@article{melillo_efimenko_genzer_2024, title={Water Droplet Equilibration on Silicone Elastomer Substrates Containing Mobile Silicones}, volume={10}, ISSN={["1520-5827"]}, url={https://doi.org/10.1021/acs.langmuir.4c02518}, DOI={10.1021/acs.langmuir.4c02518}, abstractNote={Understanding interfacial behavior at the water/silicone elastomer interface is vital in many applications, including microfluidics, antibiofouling, and self-cleaning surfaces. Silicone elastomers are not always static systems, however. Unreacted silicone molecules within a substrate may change the water-wetting behavior compared to fully reacted substrates. To investigate the impact of free silicone species at the interface, we systematically studied water wettability as a function of contact time with various silicone elastomer substrates. One set of Sylgard 184 substrates was prepared from curing at optimal stoichiometry and included doses of silicone molecules of varying molecular weights. Another set of substrates was made by mixing Sylgard 184 in imbalanced ratios to provide incomplete cross-linking. In the absence of added silicone oils, we observe a linear decrease in contact angle with time due to the evaporation of water. However, within certain molecular weight and loading levels of additional inert oils, nonlinear wetting behavior occurs as oils migrate to the interface and the system stabilizes. Similar nonlinear wetting behavior occurs without including silicone oils by mixing pure Sylgard 184 in very imbalanced mixing ratios, resulting in incomplete cross-linking. Such substrates contain unbound mobile silicone species that diffuse to the water-substrate interface. We show how the water contact angle technique can elucidate the presence of unbound silicone oils in the substrate.}, journal={LANGMUIR}, author={Melillo, Matthew J. and Efimenko, Kirill and Genzer, Jan}, year={2024}, month={Oct} }
 @article{liu_sui_harbinson_pudlo_perera_zhang_liu_ku_islam_liu_et al._2023, title={A scalable microstructure photonic coating fabricated by roll-to-roll “defects” for daytime sub-ambient passive radiative cooling}, volume={23}, ISSN={["1530-6992"]}, url={https://doi.org/10.1021/acs.nanolett.3c00111}, DOI={10.1021/acs.nanolett.3c00111}, abstractNote={The deep space's coldness (∼4 K) provides a ubiquitous and inexhaustible thermodynamic resource to suppress the cooling energy consumption. However, it is nontrivial to achieve subambient radiative cooling during daytime under strong direct sunlight, which requires rational and delicate photonic design for simultaneous high solar reflectivity (>94%) and thermal emissivity. A great challenge arises when trying to meet such strict photonic microstructure requirements while maintaining manufacturing scalability. Herein, we demonstrate a rapid, low-cost, template-free roll-to-roll method to fabricate spike microstructured photonic nanocomposite coatings with Al2O3 and TiO2 nanoparticles embedded that possess 96.0% of solar reflectivity and 97.0% of thermal emissivity. When facing direct sunlight in the spring of Chicago (average 699 W/m2 solar intensity), the coatings show a radiative cooling power of 39.1 W/m2. Combined with the coatings' superhydrophobic and contamination resistance merits, the potential 14.4% cooling energy-saving capability is numerically demonstrated across the United States.}, number={17}, journal={Nano Letters}, author={Liu, S. and Sui, C. and Harbinson, M. and Pudlo, M. and Perera, Himendra and Zhang, Zhenzhen and Liu, Ruguan and Ku, Zahyun and Islam, Md Didarul and Liu, Yuxuan and et al.}, editor={Ryu, JongEditor}, year={2023}, pages={7767–7774} }
 @article{davis_genzer_efimenko_abolhasani_2023, title={Continuous Ligand-Free Catalysis Using a Hybrid Polymer Network Support}, volume={7}, ISSN={["2691-3704"]}, url={https://doi.org/10.1021/jacsau.3c00261}, DOI={10.1021/jacsau.3c00261}, abstractNote={Although the pharmaceutical and fine chemical industries primarily utilize batch homogeneous reactions to carry out chemical transformations, emerging platforms seek to improve existing shortcomings by designing effective heterogeneous catalysis systems in continuous flow reactors. In this work, we present a versatile network-supported palladium (Pd) catalyst using a hybrid polymer of poly(methylvinylether-alt-maleic anhydride) and branched polyethyleneimine for intensified continuous flow synthesis of complex organic compounds via heterogeneous Suzuki–Miyaura cross-coupling and nitroarene hydrogenation reactions. The hydrophilicity of the hybrid polymer network facilitates the reagent mass transfer throughout the bulk of the catalyst particles. Through rapid automated exploration of the continuous and discrete parameters, as well as substrate scope screening, we identified optimal hybrid network-supported Pd catalyst composition and process parameters for Suzuki–Miyaura cross-coupling reactions of aryl bromides with steady-state yields up to 92% with a nominal residence time of 20 min. The developed heterogeneous catalytic system exhibits high activity and mechanical stability with no detectable Pd leaching at reaction temperatures up to 95 °C. Additionally, the versatility of the hybrid network-supported Pd catalyst is demonstrated by successfully performing continuous nitroarene hydrogenation with short residence times (<5 min) at room temperature. Room temperature hydrogenation yields of >99% were achieved in under 2 min nominal residence times with no leaching and catalyst deactivation for more than 20 h continuous time on stream. This catalytic system shows its industrial utility with significantly improved reaction yields of challenging substrates and its utility of environmentally-friendly solvent mixtures, high reusability, scalable and cost-effective synthesis, and multi-reaction successes.}, journal={JACS AU}, author={Davis, Bradley A. and Genzer, Jan and Efimenko, Kirill and Abolhasani, Milad}, year={2023}, month={Jul} }
 @article{im_frey_lacks_genzer_dickey_2023, title={Enhanced Triboelectric Charge Stability by Air-Stable Radicals}, volume={9}, ISSN={["2198-3844"]}, url={https://doi.org/10.1002/advs.202304459}, DOI={10.1002/advs.202304459}, abstractNote={AbstractThis paper demonstrates that air‐stable radicals enhance the stability of triboelectric charge on surfaces. While charge on surfaces is often undesirable (e.g., static discharge), improved charge retention can benefit specific applications such as air filtration. Here, it is shown that self‐assembled monolayers (SAMs) containing air‐stable radicals, 2,2,6,6‐tetramethylpiperidin‐1‐yl)oxidanyl (TEMPO), hold the charge longer than those without TEMPO. Charging and retention are monitored by Kelvin Probe Force Microscopy (KPFM) as a function of time. Without the radicals on the surface, charge retention increases with the water contact angle (hydrophobicity), consistent with the understanding that surface water molecules can accelerate charge dissipation. Yet, the most prolonged charge retention is observed in surfaces treated with TEMPO, which are more hydrophilic than untreated control surfaces. The charge retention decreases with reducing radical density by etching the TEMPO‐silane with tetrabutylammonium fluoride (TBAF) or scavenging the radicals with ascorbic acid. These results suggest a pathway toward increasing the lifetime of triboelectric charges, which may enhance air filtration, improve tribocharging for patterning charges on surfaces, or boost triboelectric energy harvesting.}, journal={ADVANCED SCIENCE}, author={Im, Sooik and Frey, Ethan and Lacks, Daniel J. and Genzer, Jan and Dickey, Michael D.}, year={2023}, month={Sep} }
 @article{frey_im_bachmann_genzer_dickey_2023, title={Patterning of a High Surface Area Liquid Metal-Carbon Composite Film Using Laser Processing}, volume={9}, ISSN={["1616-3028"]}, url={https://doi.org/10.1002/adfm.202308574}, DOI={10.1002/adfm.202308574}, abstractNote={AbstractLiquid metal is a compelling material for making soft and stretchable devices due to its high electrical conductivity and extreme stretchability. One way to pattern liquid metal is to nebulize it into small droplets, spray it onto a surface as a film, and then use a laser to “sinter” it into circuit patterns. Here, it is shown that including poly(amic acid) in the spray‐deposited film has multiple benefits: it (1) allows the unsintered regions to be removed easily, (2) lowers the power required for sintering, (3) converts to carbon upon exposure to create a carbon‐metal composite, and (4) increases the surface area of the film by 2632% compared to bulk EGaIn. The conductive liquid metal‐carbon circuits can also be transferred to a soft substrate to produce stretchable conductors. The circuits slightly increase in conductivity up to ≈30% strain and then decrease such that by 100% strain, the resistance is only ≈1.02 times its initial resistance. Lastly, the film is highly reactive with water molecules in the air, increasing in resistance over time in humid conditions. The high reactivity and surface area of the film indicate potential applications in batteries, catalysts, and capacitors. Meanwhile, the facile patterning indicates potential applications in soft circuits.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Frey, Ethan J. and Im, Sooik and Bachmann, Adam L. and Genzer, Jan and Dickey, Michael D.}, year={2023}, month={Sep} }
 @article{machikiti_pourdeyhimi_genzer_efimenko_2023, title={Tuning Interfacial Adhesion in Polyester/Polyamide Systems}, volume={7}, ISSN={["1520-5045"]}, url={https://doi.org/10.1021/acs.iecr.3c01517}, DOI={10.1021/acs.iecr.3c01517}, abstractNote={Polymer–polymer adhesion is critical in polymer processing and application areas where lamination, welding, composites, blending, and coextrusion are involved. Polyethylene terephthalate/polyamide (PET/PA) pairs are widely used to produce bicomponent fibers. The strong adhesion due to the formation of chemical bonds in the interfacial region limits post-production fiber processing. The adhesion strength in the PET/PA systems showed that PET/PA66 had the highest adhesion energy, followed by PET/PA6, PET/PA11, and PET/PA12 for all processing conditions. We developed a method that enables adhesion control by introducing a poly(octadecene-alt-maleic anhydride) (POMA) alternating copolymer by either direct interfacial modification or addition into the PET phase. Upon POMA introduction to the system, the reduction in interfacial adhesion strength between PET and polyamides is observed. We established the relationship between adhesion strengths in PET/polyamide systems, processing conditions, and concentration of the POMA modifier.}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Machikiti, Zvikomborero and Pourdeyhimi, Behnam and Genzer, Jan and Efimenko, Kirill}, year={2023}, month={Jul} }
 @article{kannan_genzer_2023, title={UV- and thermally-active small bi-functional gelator for creating gradient polymer network coatings}, volume={18}, ISSN={["1559-4106"]}, DOI={10.1116/6.0002268}, abstractNote={We present a versatile one-pot synthesis method for creating surface-anchored orthogonal gradient networks using a small bi-functional gelator, 4-azidosulfonylphenethyltrimethoxysilane (4-ASPTMS). The sulfonyl azide (SAz) group of 4-ASPTMS is UV (≤254 nm) and thermally active (≥100 °C) and, thus, enables us to vary the cross-link density in orthogonal directions by controlling the activation of SAz groups via UV and temperature means. We deposit a thin layer (∼200 nm) of a mixture comprising ∼90% precursor polymer and ∼10% 4-ASPTMS in a silicon wafer. Upon UV irradiation or annealing the layers, SAz releases nitrogen by forming singlet and triplet nitrenes that concurrently react with any C–H bond in the vicinity leading to sulfonamide cross-links. Condensation among trimethoxy groups in the bulk connects 4-ASPTMS units and completes the cross-linking. Simultaneously, 4-ASPTMS near the substrate reacts with surface-bound –OH motifs that anchor the cross-linked polymer chains to the substrate. We demonstrate the generation of orthogonal gradient network coatings exhibiting cross-link density (or stiffness) gradients in orthogonal directions using such a simple process.}, number={1}, journal={BIOINTERPHASES}, author={Kannan, Pandiyarajan Chinnayan and Genzer, Jan}, year={2023}, month={Jan} }
 @article{machikiti_pourdeyhimi_genzer_efimenko_2022, title={Controlling PA6/PET adhesion to facilitate interfacial fracture}, volume={171}, ISSN={["1873-1945"]}, DOI={10.1016/j.eurpolymj.2022.111196}, abstractNote={Microfibers get often produced in the form of bicomponent polymer systems. The materials of choice are Nylon 6 (PA6) and poly(ethylene terephthalate) (PET). This combination of PA6 and PET is preferable because of its beneficial attributes (i.e., thermal stability, mechanical strength, etc.). PA6 and PET exhibit high adhesion when processed at elevated temperatures due to chemical bonds formation by aminolysis of the ester group in PET with a secondary amine in PA6. These fibers are split/fibrillated by mechanical energy (hydroentangling or needle punching). For energy input, it is desirable to have adhesion between the PA6 and PET materials that is not too strong to allow for easy polymer splitting. Therefore, we developed a method for tailoring the PA6/PET interface adhesion by adding modifiers that react preferentially with the PA6 component. The reactivity between PA6 and PET was investigated by spin coating thin films of PA6 and PET on silicon wafers and annealing them at high temperatures. The reaction between PET and small molecules containing secondary amines (i.e., caprolactam, diallyamine, diethylamine, and diisopropylamine) shows a chemical bond between the ester group in PET and the secondary amine group. The poly(styrene-alt-maleic anhydride) (PSMA) and poly(octadecene-alt-maleic anhydride) (POMA) were chosen as model polymer interfacial modifiers. The feasibility of modifying secondary amines is examined by reacting the two modifiers, PSMA and POMA, with small molecules containing secondary amine groups. PA6 and PET display high fracture toughness (i.e., adhesion strength) at elevated temperatures and longer annealing times because of strong interactions between the amine and ester groups in PA6 and PET, respectively. We then assess the adhesion strength between PA6 and PET modified with PSMA and POMA. Both modifiers reduce interfacial adhesion strength between PA6 and PET. Therefore, it is feasible to tailor adhesion at the PA6/PET interface, which could prove helpful in microfibers production.}, journal={EUROPEAN POLYMER JOURNAL}, author={Machikiti, Zvikomborero and Pourdeyhimi, Behnam and Genzer, Jan and Efimenko, Kirill}, year={2022}, month={May} }
 @article{mu_genzer_gorman_2022, title={Degradable Anti-Biofouling Polyester Coatings with Controllable Lifetimes}, volume={1}, ISSN={["0743-7463"]}, url={https://doi.org/10.1021/acs.langmuir.1c02822}, DOI={10.1021/acs.langmuir.1c02822}, abstractNote={To achieve degradable, anti-biofouling coatings with longer lifetimes and better mechanical properties, we synthesized a series of degradable co-polyesters composed of cyclic ketene acetals, di-(ethylene glycol) methyl ether methacrylate, and a photoactive curing agent, 4-benzoylphenyl methacrylate, using a radical ring-opening polymerization. The precursor co-polyesters were spin-coated on a benzophenone-functionalized silicon wafer to form ca. 60 nm films and drop-casted on glass to form ∼32 μm films. The copolymers were cross-linked via UV irradiation at 365 nm. The degradation of films was studied by immersing the specimens in aqueous buffers of different pH values. The results show that both the pH of buffer solutions and gel fractions of networks affect the degradation rate. The coatings show good bovine serum albumin resistance capability. By adjusting the fractions of monomers, the degradation rate and degree of hydration (e.g., swelling ratio) are controllable.}, number={4}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Mu, Gaoyan and Genzer, Jan and Gorman, Christopher B.}, year={2022}, month={Jan} }
 @article{davis_bennett_genzer_efimenko_abolhasani_2022, title={Intensified Hydrogenation in Flow Using a Poly(beta-cyclodextrin) Network-Supported Catalyst}, volume={11}, ISSN={["2168-0485"]}, url={https://doi.org/10.1021/acssuschemeng.2c05467}, DOI={10.1021/acssuschemeng.2c05467}, abstractNote={The intersection of heterogeneous catalysis and flow chemistry is of great importance for the emerging distributed manufacturing of specialty chemicals. Specifically, continuous production of aryl amines is an essential step for on-demand and on-site manufacturing of fine chemicals. This work presents a heterogeneous flow chemistry route for accelerated chemoselective hydrogenation of nitroarenes using a poly(β-cyclodextrin) network-supported palladium catalyst. The developed packed-bed flow reactor enables the selective hydrogenation of a rationally selected library of nitroarenes with >99% yield at room temperature and short residence times (1 min). Utilizing sodium borohydride as the hydrogen carrier in a pressurized packed-bed flow reactor allows safe and efficient delivery of hydrogen to nitroarene molecules. We demonstrate the robustness and versatility of the flow reactor packed with the network-supported catalyst through its consistently high reaction yield over a 3 day run and its reusability and stability in several solvent mixtures with a single-reactor aryl amine manufacturing throughput of up to 31.5 g/day. Furthermore, the catalytic packed-bed reactor is used in a case study for a two-step telescopic synthesis of a critical intermediate for the antibacterial drug linezolid, further supporting its utility as an industrially relevant catalyst for the broad application of catalytic hydrogenations in flow.}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Davis, Bradley A. and Bennett, Jeffrey A. and Genzer, Jan and Efimenko, Kirill and Abolhasani, Milad}, year={2022}, month={Nov} }
 @article{ramesh_davis_roros_zhou_he_gao_menegatti_khan_genzer_2022, title={Nonwoven Membranes with Infrared Light-Controlled Permeability}, volume={9}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.2c13280}, abstractNote={This study presents the development of the first composite nonwoven fiber mats (NWFs) with infrared light-controlled permeability. The membranes were prepared by coating polypropylene NWFs with a photothermal layer of poly(N-isopropylacrylamide) (PNIPAm)-based microgels impregnated with graphene oxide nanoparticles (GONPs). This design enables "photothermal smart-gating" using light dosage as remote control of the membrane's permeability to electrolytes. Upon exposure to infrared light, the GONPs trigger a rapid local increase in temperature, which contracts the PNIPAm-based microgels lodged in the pore space of the NWFs. The contraction of the microgels can be reverted by cooling from the surrounding aqueous environment. The efficient conversion of infrared light into localized heat by GONPs coupled with the phase transition of the microgels above the lower critical solution temperature (LCST) of PNIPAm provide effective control over the effective porosity, and thus the permeability, of the membrane. The material design parameters, namely the monomer composition of the microgels and the GONP-to-microgel ratio, enable tuning the permeability shift in response to IR light; control NWFs coated with GONP-free microgels displayed thermal responsiveness only, whereas native NWFs showed no smart-gating behavior at all. This technology shows potential toward processing temperature-sensitive bioactive ingredients or remote-controlled bioreactors.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ramesh, Srivatsan and Davis, Jack and Roros, Alexandra and Zhou, Chuanzhen and He, Nanfei and Gao, Wei and Menegatti, Stefano and Khan, Saad and Genzer, Jan}, year={2022}, month={Sep} }
 @article{rittschof_orihuela_genzer_efimenko_2022, title={PDMS networks meet barnacles: a complex and often toxic relationship}, volume={11}, ISSN={["1029-2454"]}, url={https://doi.org/10.1080/08927014.2022.2145471}, DOI={10.1080/08927014.2022.2145471}, abstractNote={Abstract The biological impact of chemical formulations used in various coating applications is essential in guiding the development of new materials that directly contact living organisms. To illustrate this point, an investigation addressing the impact of chemical compositions of polydimethylsiloxane networks on a common platform for foul-release biofouling management coatings was conducted. The acute toxicity of network components to barnacle larvae, the impacts of aqueous extracts of crosslinker, silicones and organometallic catalyst on trypsin enzymatic activity, and the impact of assembled networks on barnacle adhesion was evaluated. The outcomes of the study indicate that all components used in the formulation of the silicone network alter trypsin enzymatic activity and have a range of acute toxicity to barnacle larvae. Also, the adhesion strength of barnacles attached to PDMS networks correlates to the network formulation protocol. This information can be used to assess action mechanisms and risk–benefit analysis of PDMS networks.}, journal={BIOFOULING}, author={Rittschof, Daniel and Orihuela, Beatriz and Genzer, Jan and Efimenko, Kirill}, year={2022}, month={Nov} }
 @article{barbieri_cutright_ramesh_khan_efimenko_genzer_menegatti_2022, title={Potent Antibacterial Composite Nonwovens Functionalized with Bioactive Peptides and Polymers}, volume={8}, ISSN={["2196-7350"]}, url={https://doi.org/10.1002/admi.202201061}, DOI={10.1002/admi.202201061}, abstractNote={AbstractThis study presents a set of strategies for producing potent antibacterial fabrics by functionalizing nonwoven fabrics (NWFs) with antimicrobial peptides and polymers (AMPs). The incorporation of AMPs is initially optimized on 2D substrates by evaluating conjugation on a poly(maleic anhydride) copolymer coating versus adsorption on polycationic/anionic films and microgels. The evaluation of the resulting surfaces against S. aureus and E. coli highlights the superior antibacterial activity of poly‐ionic films loaded with daptomycin and polymyxin B as well as microgels featuring controlled release of bacitracin and polymyxin B. These formulations are translated onto spun‐bond polypropylene and poly(ethylene terephthalate) NWFs. The poly‐ionic coatings are either covalently anchored or physically adsorbed onto the surface of the fibers, while the microgels and antibacterial polymers are adsorbed and photo‐crosslinked thereon using a ultraviolet (UV)‐crosslinkable benzophenone‐based polymer. Selected formulations loaded with bacitracin and polymyxin B afford a 105‐fold reduction of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in artificial sweat, respectively, on par with commercial antibacterial NWFs. The proposed antibacterial fabric, however, outperforms its commercial counterparts in terms of biocompatibility, showing virtually no adverse effect on human epidermal keratinocytes. Collectively, these results demonstrate affordable and scalable routes for developing antimicrobial NWFs that efficiently eliminate resilient pathogenic bacteria.}, journal={ADVANCED MATERIALS INTERFACES}, author={Barbieri, Eduardo and Cutright, Camden C. and Ramesh, Srivatsan and Khan, Saad A. and Efimenko, Kirill and Genzer, Jan and Menegatti, Stefano}, year={2022}, month={Aug} }
 @misc{ramesh_khan_park_ford_menegatti_genzer_2022, title={Self-healing and repair of fabrics: A comprehensive review of the application toolkit}, volume={54}, ISSN={["1873-4103"]}, DOI={10.1016/j.mattod.2021.11.016}, abstractNote={Self-healing fabrics respond to chemical and physical damage by restoring functional, structural, and morphological features. We present a comprehensive review of textile hybrids or composites capable of self-healing and repairing fabrics against damages across the micro- (µm), meso- (µm – mm), and macro-scale (>mm). The reviewed literature is organized in three sections presenting (i) the chemistry and fabrication principles of designing self-healing fabrics against increasing size scales of repair, (ii) stimuli-driven and autonomous healing, and (iii) the methods to characterize the recovery of wettability, barrier, morphological, mechanical, and other properties. The discussion of mainstream methods for developing self-healing fabrics focuses on coatings, composites, and specialized fabrication techniques required as the damage size grows from µm to mm to >mm. The section on stimuli-driven repair and autonomous recovery discusses the time scales associated with different damage repair, showing how external stimuli provide a higher driving force towards healing and accelerate material restoration than autonomous recovery. Finally, an array of optical, mechanical, and functional characterization techniques is discussed to evaluate the recovery yield and understand the repair mechanisms of the various fabrics. This review demonstrates the virtually limitless uses of next-generation self-healing systems, from separations to protective clothing, anti-fouling, and self-cleaning.}, journal={MATERIALS TODAY}, author={Ramesh, Srivatsan and Khan, Saad and Park, Yaewon and Ford, Ericka and Menegatti, Stefano and Genzer, Jan}, year={2022}, month={Apr}, pages={90–109} }
 @misc{shaw_kuriakose_cheeseman_dickey_genzer_christofferson_crawford_mcconville_chapman_truong_et al._2021, title={Antipathogenic properties and applications of low-dimensional materials}, volume={12}, ISSN={["2041-1723"]}, url={https://doi.org/10.1038/s41467-021-23278-7}, DOI={10.1038/s41467-021-23278-7}, abstractNote={AbstractA major health concern of the 21st century is the rise of multi-drug resistant pathogenic microbial species. Recent technological advancements have led to considerable opportunities for low-dimensional materials (LDMs) as potential next-generation antimicrobials. LDMs have demonstrated antimicrobial behaviour towards a variety of pathogenic bacterial and fungal cells, due to their unique physicochemical properties. This review provides a critical assessment of current LDMs that have exhibited antimicrobial behaviour and their mechanism of action. Future design considerations and constraints in deploying LDMs for antimicrobial applications are discussed. It is envisioned that this review will guide future design parameters for LDM-based antimicrobial applications.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Shaw, Z. L. and Kuriakose, Sruthi and Cheeseman, Samuel and Dickey, Michael D. and Genzer, Jan and Christofferson, Andrew J. and Crawford, Russell J. and McConville, Chris F. and Chapman, James and Truong, Vi Khanh and et al.}, year={2021}, month={Jun} }
 @article{bennett_davis_ramezani_genzer_efimenko_abolhasani_2021, title={Continuous Ligand-Free Suzuki-Miyaura Cross-Coupling Reactions in a Cartridge Flow Reactor Using a Gel-Supported Catalyst}, volume={60}, ISSN={["0888-5885"]}, url={https://doi.org/10.1021/acs.iecr.1c01531}, DOI={10.1021/acs.iecr.1c01531}, abstractNote={The Suzuki–Miyaura cross-coupling reaction is one of the most important reactions for pharmaceutical and fine chemical synthesis, performed using both homogeneous and heterogeneous catalysis. In this work, we cross-link poly(methylhydrosiloxane) (PMHS) with tri(ethylene glycol divinyl ether) to create a versatile and readily accessible gel catalyst support for Suzuki–Miyaura cross-coupling reactions in a pseudoheterogeneous manner. The Si–H units present on the PMHS backbone act dually as the cross-linking site and the reducing agent to anchor and reduce palladium(II) acetate to active palladium(0). The PMHS-supported Pd catalyst is then packed into a stainless-steel flow reactor to create a cartridgelike reactor for the continuous operation of a model Suzuki–Miyaura cross-coupling reaction. We systematically investigate the role of reaction temperature, catalyst loading, cross-linking density, and gel particle size on the transient and steady-state behavior of the cartridge flow reactor through an automated flow chemistry platform. The PMHS-supported catalytic particles demonstrate minimal deactivation and leaching over a continuous (80 h) Suzuki–Miyaura cross-coupling reaction at a 30 min nominal residence time at a relatively high reaction temperature of 95 °C. The developed modular flow chemistry strategy equipped with the cartridge flow reactor enables accelerated studies of the fundamental and applied characteristics of gel-supported catalysts while providing increased safety, higher throughput, and removal of the separation step needed for catalyst recovery compared to homogeneous cross-coupling reactions in batch reactors.}, number={26}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, publisher={American Chemical Society (ACS)}, author={Bennett, Jeffrey A. and Davis, Bradley A. and Ramezani, Mahdi and Genzer, Jan and Efimenko, Kirill and Abolhasani, Milad}, year={2021}, month={Jul}, pages={9418–9428} }
 @article{ko_truong_woo_dickey_hsiao_genzer_2021, title={Counterpropagating Gradients of Antibacterial and Antifouling Polymer Brushes}, volume={12}, ISSN={["1526-4602"]}, url={https://doi.org/10.1021/acs.biomac.1c01386}, DOI={10.1021/acs.biomac.1c01386}, abstractNote={We report on the formation of counterpropagating density gradients in poly([2-dimethylaminoethyl] methacrylate) (PDMAEMA) brushes featuring spatially varying quaternized and betainized units. Starting with PDMAEMA brushes with constant grafting density and degree of polymerization, we first generate a density gradient of quaternized units by directional vapor reaction involving methyl iodide. The unreacted DMAEMA units are then betainized through gaseous-phase betainization with 1,3-propanesultone. The gas reaction of PDMAEMA with 1,3-propanesultone eliminates the formation of byproducts present during the liquid-phase modification. We use the counterpropagating density gradients of quaternized and betainized PDMAEMA brushes in antibacterial and antifouling studies. Completely quaternized and betainized brushes exhibit antibacterial and antifouling behaviors. Samples containing 12% of quaternized and 85% of betainized units act simultaneously as antibacterial and antifouling surfaces.}, journal={BIOMACROMOLECULES}, publisher={American Chemical Society (ACS)}, author={Ko, Yeongun and Truong, Vi Khanh and Woo, Sun Young and Dickey, Michael D. and Hsiao, Lilian and Genzer, Jan}, year={2021}, month={Dec} }
 @article{clark_thacker_mcgill_miles_westmoreland_efimenko_genzer_santiso_2021, title={DFT Analysis of Organotin Catalytic Mechanisms in Dehydration Esterification Reactions for Terephthalic Acid and 2,2,4,4-Tetramethyl-1,3-cyclobutanediol}, volume={125}, ISSN={["1520-5215"]}, url={https://doi.org/10.1021/acs.jpca.1c00850}, DOI={10.1021/acs.jpca.1c00850}, abstractNote={Polyesters synthesized from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD) and terephthalic acid (TPA) are improved alternatives to toxic polycarbonates based on bisphenol A. In this work, we use ωB97X-D/LANL2DZdp calculations, in the presence of a benzaldehyde polarizable continuum model solvent, to show that esterification of TMCD and TPA will reduce and subsequently dehydrate a dimethyl tin oxide catalyst, becoming ligands on the now four-coordinate complex. This reaction then proceeds most plausibly by an intramolecular acyl-transfer mechanism from the tin complex, aided by a coordinated proton donor such as hydronium. These findings are a key first step in understanding polyester synthesis and avoiding undesirable side reactions during production.}, number={23}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, publisher={American Chemical Society (ACS)}, author={Clark, Jennifer A. and Thacker, Pranav J. and McGill, Charles J. and Miles, Jason R. and Westmoreland, Phillip R. and Efimenko, Kirill and Genzer, Jan and Santiso, Erik E.}, year={2021}, month={Jun}, pages={4943–4956} }
 @article{castillo_dickey_gorman_genzer_efimenko_2021, title={Deposition of silicate coatings on poly(ethylene terephthalate) for improved scratch and solvent resistance}, volume={10}, ISSN={["1097-4628"]}, url={https://doi.org/10.1002/app.51800}, DOI={10.1002/app.51800}, abstractNote={AbstractThe surface of poly(ethylene terephthalate) (PET) films crystallizes when exposed to a broad class of organic solvents (protic polar, aprotic polar, and non‐polar). This phenomenon leads to irreversible changes in transparency and mechanical properties. It also limits PET films and coatings in applications including electronics, medicine, packaging, and construction. This work describes a method to impart solvent resistance to the PET surface by depositing a silicate film. This coating enables many post‐functionalization options, including those that tune wettability or impart antifouling characteristics to the parent PET surface. It also endows PET surface resistance to organic solvent exposure without affecting the overall mechanical and optical properties of the PET. Additionally, the silicate layer improves the scratch resistance of PET surfaces.}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, publisher={Wiley}, author={Castillo, Gilbert A. and Dickey, Michael D. and Gorman, Christopher B. and Genzer, Jan and Efimenko, Kirill}, year={2021}, month={Oct} }
 @article{poblete_mondal_ma_dickey_genzer_zhu_2022, title={Direct measurement of rate-dependent mode I and mode II traction-separation laws for cohesive zone modeling of laminated glass}, volume={279}, ISSN={["1879-1085"]}, DOI={10.1016/j.compstruct.2021.114759}, abstractNote={This paper reports a combined experimental-modeling study on the adhesion at glass/poly(vinyl butyral) (PVB) interfaces. PVB is a critical component in laminated glasses that provides impact resistance and prevents spallation in the event of glass breakage. We characterize the mode I (normal) and mode II (shear) interfacial fracture behaviors in glass/PVB/glass laminates and obtained independent cohesive (traction–separation) laws for the two modes. We observe a pronounced rate dependence of both traction-separation laws. Specifically, with increasing loading rate, the interfacial stiffness, the peak stress, and the fracture toughness increase while the critical opening or shear displacement decreases. These measured traction-separation laws are used as inputs in finite element analysis to predict the mechanical behavior of the peel test, which agrees reasonably well with the experimental results. Finite element analysis of a glass laminate subjected to impact loading demonstrates how the measured interfacial properties can be used to predict the mechanical behavior and failure of laminated glass.}, journal={COMPOSITE STRUCTURES}, author={Poblete, Felipe R. and Mondal, Kunal and Ma, Yinong and Dickey, Michael D. and Genzer, Jan and Zhu, Yong}, year={2022}, month={Jan} }
 @article{ramesh_davis_roros_eiben_fabiani_smith_reynolds_pourdeyhimi_khan_genzer_et al._2021, title={Dual-Responsive Microgels for Structural Repair and Recovery of Nonwoven Membranes for Liquid Filtration}, volume={3}, ISSN={["2637-6105"]}, url={https://doi.org/10.1021/acsapm.0c01360}, DOI={10.1021/acsapm.0c01360}, abstractNote={This study presents dual-responsive colloidal microgels to repair nonwoven fiber mats (NWFs) and recover their native morphological and functional properties. The formulation comprises poly(N-isopr...}, number={3}, journal={ACS APPLIED POLYMER MATERIALS}, publisher={American Chemical Society (ACS)}, author={Ramesh, Srivatsan and Davis, Jack and Roros, Alexandra and Eiben, Justin and Fabiani, Thomas and Smith, Ryan and Reynolds, Lewis and Pourdeyhimi, Behnam and Khan, Saad and Genzer, Jan and et al.}, year={2021}, month={Mar}, pages={1508–1517} }
 @article{mu_pandiyarajan_lu_weaver_genzer_gorman_2021, title={Dynamic Surfaces-Degradable Polyester Networks that Resist Protein Adsorption}, volume={37}, ISSN={["0743-7463"]}, url={https://doi.org/10.1021/acs.langmuir.1c00890}, DOI={10.1021/acs.langmuir.1c00890}, abstractNote={We synthesized a series of novel degradable alternating copolyesters composed of diglycolic anhydride (DGA) and two epoxides, epoxymethoxytriethylene glycol (ETEG) and a photoactive crosslinking agent epoxy benzophenone (EBP). After UV crosslinking, soaking the films in a good solvent (tetrahydrofuran) removed uncrosslinked material, and the resulting film gel fractions were calculated. These network films were then degraded in buffer solutions of varying pH values. The degradation of networks with lower gel fraction (fewer crosslinks) was faster and followed first-order kinetics. In contrast, the denser network degraded slower and followed zeroth-order kinetics. The lower gel fraction networks possess a higher swelling ratio and resist bovine serum albumin (BSA) adsorption better by entropic shielding and faster degradation. In comparison, higher gel fraction networks with higher EBP mole fractions adsorb more BSA due to hydrophobic interactions and slower degradation.}, number={30}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Mu, Gaoyan and Pandiyarajan, C. K. and Lu, Xiuyuan and Weaver, Matt and Genzer, Jan and Gorman, Christopher B.}, year={2021}, month={Aug}, pages={8978–8988} }
 @article{zboray_efimenko_jones_genzer_2021, title={Functional Gels Containing Hydroxamic Acid Degrade Organophosphates in Aqueous Solutions}, volume={60}, ISSN={["0888-5885"]}, url={https://doi.org/10.1021/acs.iecr.1c01374}, DOI={10.1021/acs.iecr.1c01374}, abstractNote={We synthesized poly(maleic anhydride-co-methyl vinyl ether) (PMAMVE) gels and functionalized them to form hydroxamic acid functional groups. We evaluated the performance of the gels in decomposing dimethyl nitrophenyl phosphate (DMNP). We monitored organophosphate degradation kinetics as a function of gel chemical composition, cross-linking density, and solution pH and applied Thiele modulus analysis to determine the importance of transport phenomena related to the particulate gel size. The decomposition of DMNP in the maleic anhydride gels followed pseudo-first-order kinetics for all studied conditions. The performance was influenced by the spatial confinement of the hydroxamic acid groups inside the gel. The gels made of PMAMVE copolymers modified with hydroxamic acid offer a robust new system with high degradation efficiency, scalability, and preparation simplicity.}, number={24}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, publisher={American Chemical Society (ACS)}, author={Zboray, Steven and Efimenko, Kirill and Jones, Jacob L. and Genzer, Jan}, year={2021}, month={Jun}, pages={8799–8811} }
 @article{liu_islam_ku_boyd_zhong_urbas_smith_derov_nguyen_kim_et al._2021, title={Novel computational design of high refractive index nanocomposites and effective refractive index tuning based on nanoparticle morphology effect}, volume={223}, ISSN={["1879-1069"]}, url={https://doi.org/10.1016/j.compositesb.2021.109128}, DOI={10.1016/j.compositesb.2021.109128}, abstractNote={This study introduces a method to predict the refractive index (RI) of nanocomposites with the Finite Elements Analysis (FEA) based on the Fabry-Pérot interference. The efficacy was verified by comparing the estimated composites' RI with the available data in the literature. In the experimental verification, the FEA-based prediction showed closer results with the measurement as compared to the effective medium approximation (EMA) approaches, which are prevalently used to predict the physical properties of nanocomposites. Due to the modeling capability, the FEA-method could investigate the effect of the nanoparticle morphology (particle size, shape, and orientation) and distribution. Large particle size, particle agglomeration in high electric-field amplitude region, and particle elongation along the light oscillating direction are found to be the major factors to enhance the RI of composites. The underlying mechanism of RI changing is attributed to the light scattering by embedded nanoparticles, which provides one potential real-time RI tuning schematic.}, journal={COMPOSITES PART B-ENGINEERING}, publisher={Elsevier BV}, author={Liu, Sipan and Islam, Md Didarul and Ku, Zahyun and Boyd, Darryl A. and Zhong, Yaxu and Urbas, Augustine M. and Smith, Evan and Derov, John and Nguyen, Vinh Q. and Kim, Woohong and et al.}, year={2021}, month={Oct} }
 @article{cutright_harris_ramesh_khan_genzer_menegatti_2021, title={Surface-Bound Microgels for Separation, Sensing, and Biomedical Applications}, volume={8}, ISSN={["1616-3028"]}, url={https://doi.org/10.1002/adfm.202104164}, DOI={10.1002/adfm.202104164}, abstractNote={AbstractThis study presents a comprehensive survey of microgel‐coated materials and their functional behavior, describing the complex interplay between the physicochemical and mechanical properties of the microgels and the chemical and morphological features of substrates. The cited literature is articulated in four main sections: i) properties of 2D and 3D substrates, ii) synthesis, modification, and characterization of the microgels, iii) deposition techniques and surface patterning, and iv) application of microgel‐coated surfaces focusing on separations, sensing, and biomedical applications. Each section discusses – by way of principles and examples – how the various design parameters work in concert to deliver functionality to the composite systems. The case studies presented herein are viewed through a multi‐scale lens. At the molecular level, the surface chemistry and the monomer make‐up of the microgels endow responsiveness to environmental and artificial physical and chemical cues. At the micro‐scale, the response effects shifts in size, mechanical, and optical properties, and affinity towards species in the surrounding liquid medium, ranging from small molecules to cells. These phenomena culminate at the macro‐scale in measurable, reversible, and reproducible effects, aiming in a myriad of directions, from lab‐scale to industrial applications.}, number={47}, journal={ADVANCED FUNCTIONAL MATERIALS}, publisher={Wiley}, author={Cutright, Camden C. and Harris, Jacob L. and Ramesh, Srivatsan and Khan, Saad A. and Genzer, Jan and Menegatti, Stefano}, year={2021}, month={Aug} }
 @article{woo_pandiyarajan_genzer_2021, title={Tuning the Properties of Surface-Anchored Polymer Networks by Varying the Concentration of a Thermally Activated Cross-Linker, Annealing Time, and Temperature in a One-Pot Reaction}, volume={3}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.1c00890}, abstractNote={We investigate the properties of surface-anchored polymer networks created via one-pot synthesis using thermally active 6-azidosulfonylhexyltriethoxysilane (6-ASHTES). 6-ASHTES is a bifunctional gelator that undergoes cross-linking and surface-anchoring reactions when annealed above 100 °C. We employ a poly(vinylpyrrolidone) (PVP) with different molecular weights (10–1300 kDa) as a model system to examine the effect of 6-ASHTES concentration, annealing time, and annealing temperature on gel formation. A thin film of PVP/6-ASHTES mixture is deposited on a clean silicon wafer and annealed to form network layers. Spectroscopic ellipsometry measures the film thickness of the cross-linked layers from which the gel fraction and swelling ratio are determined. The gel fraction of PVP in the network can be "dialed in" by varying the annealing time, temperature, and concentration of 6-ASHTES in the PVP/6-ASHTES mixture. We use a simple Monte Carlo simulation model to describe cross-linking as a function of cross-linker concentration, reaction rate, reaction time, and polymer length. The trends obtained from the model simulations are in qualitative agreement with the experimental data.}, number={11}, journal={ACS APPLIED POLYMER MATERIALS}, author={Woo, Sun Young and Pandiyarajan, C. K. and Genzer, Jan}, year={2021}, month={Nov}, pages={5568–5577} }
 @article{pandiyarajan_genzer_2021, title={UV- and Thermally-Active Bifunctional Gelators Create Surface-Anchored Polymer Networks}, volume={6}, ISSN={["1521-3927"]}, DOI={10.1002/marc.202100266}, abstractNote={AbstractA versatile one‐step synthesis of surface‐attached polymer networks using small bifunctional gelators (SBG), namely 4‐azidosulfonylphenethyltrimethoxysilane (4‐ASPTMS) and 6‐azidosulfonylhexyltriethoxysilane (6‐ASHTES) is reported. A thin layer (≈200 nm) of a mixture comprising ≈90% precursor polymer and 10% of 4‐ASPTMS or 10% 6‐ASHTES on a silicon wafer is deposited. Upon UV irradiation (≈l–254 nm) or annealing (>100 °C) layers, sulfonyl azides (SAz) release nitrogen by forming singlet and triplet nitrenes that concurrently react with any C─H bond in the vicinity resulting in sulfonamide crosslinks. Condensation among tri‐alkoxy groups (i.e., methoxy or ethoxy) in bulk connects the SBG units, which completes the crosslinking. Concurrently, when such functionalities react with hydroxyl groups at the surface, which enable the covalent attachment of the crosslinked polymer chains. A systematic investigation on reaction mechanism and gel formation using spectroscopic ellipsometry (SE) and Fourier‐transform infrared spectroscopy in the attenuated total reflection mode (FTIR‐ATR) is performed. Analogous thermally initiated gelation for both 4‐ASPTMS and 6‐ASHTES is found. The 6‐ASHTES is UV inactive at ≈l–254 nm, while the 4‐ASPTMS is active and forms gels. The difference is attributed to the aromatic nature of 4‐ASPTMS that absorb UV light at ≈l–254 nm due to π–π* transition.}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Pandiyarajan, Chinnayan Kannan and Genzer, Jan}, year={2021}, month={Jun} }
 @article{ko_christau_klitzing_genzer_2020, title={Charge Density Gradients of Polymer Thin Film by Gaseous Phase Quaternization}, volume={9}, ISSN={["2161-1653"]}, DOI={10.1021/acsmacrolett.9b00930}, abstractNote={We report on the rapid formation of charge density gradients in polymer films by exposing poly([2-dimethylaminoethyl] methacrylate) (PDMAEMA) films resting on flat silica substrates to methyl iodide (i.e., MI, also known as iodomethane) vapors. We adjust the charge gradient by varying the MI concentration in solution and the process time. The thickness of the parent PDMAEMA film does not affect the diffusion of MI through and the reaction kinetics in the films. Instead, the diffusion of MI through the gaseous phase constitutes the limiting step in the overall process.}, number={2}, journal={ACS MACRO LETTERS}, author={Ko, Yeongun and Christau, Stephanie and Klitzing, Regine and Genzer, Jan}, year={2020}, month={Feb}, pages={158–162} }
 @article{schmitz_wohl_tiemsin_genzer_2020, title={Controlled heating and alignment platform enhances versatility in colloidal probe fabrication}, volume={91}, ISSN={["1089-7623"]}, DOI={10.1063/1.5111387}, abstractNote={A colloidal probe, comprising a colloidal particle attached to an atomic force microscope cantilever, is employed to measure interaction forces between the particle and a surface. It is possible to change or even destroy a particle while attaching it to a cantilever, thus limiting the types of systems to which the colloidal probe technique may be applied. Here, we present the Controlled Heating and Alignment Platform (CHAP) for fabricating colloidal probes without altering the original characteristics of the attached particle. The CHAP applies heat directly to the atomic force microscope chip to rapidly and precisely control the cantilever temperature. It minimizes particle heating and enables control over the viscosity of the thermoplastic adhesive to prevent it from contaminating the particle surface. 3D-printed components made the CHAP compatible with standard optical microscopes and streamlined the fabrication process, while increasing the platform’s versatility. To demonstrate the utility of CHAP, we conducted a case study using a thermoplastic wax adhesive to fabricate colloidal probes bearing polystyrene and silica particles between 0.7 and 40 μm in diameter. We characterized the properties and interactions of the adhesive and particles, as well as the properties of the completed probes, to demonstrate the retention of particle features throughout fabrication. Pull-off tests with CHAP’s probes measured adhesive force values in the expected ranges and demonstrated that particles were firmly attached to the cantilevers.}, number={1}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Schmitz, Russell C. and Wohl, Christopher J. and Tiemsin, Pacita I. and Genzer, Jan}, year={2020}, month={Jan} }
 @article{islam_kim_ko_ku_boyd_smith_nguyen_myers_baker_kim_et al._2020, title={Design of High Efficient Mid‐Wavelength Infrared Polarizer on ORMOCHALC Polymer}, volume={305}, ISSN={1438-7492 1439-2054}, url={http://dx.doi.org/10.1002/mame.202000033}, DOI={10.1002/mame.202000033}, abstractNote={AbstractWhile an organically modified chalcogenide (ORMOCHALC) can be used to fabricate a polymeric mid‐wavelength infrared (MWIR) polarizer with competitive extinction ratio compared to the commercial wire‐grid polarizers, which are composed of fragile inorganic materials, there is still a knowledge gap regarding the systematic design process to obtain high transmission efficiency and extinction ratio. To this end, a computational parameter study for design optimization is conducted with the geometric parameters of the bilayer grating ORMOCHALC polarizer. The computational study shows that the Fabry–Pérot cavity is the primary mechanism that determines the transmission behaviors and the extinction ratio. A bilayer grating design, guided by the parameter study, is realized through the thermal nanoimprint and metal deposition processes. The extinction ratios measured with the Fourier‐transform infrared are 245, 304, and 351 at the wavelength of 3, 4, and 5 µm, respectively. Compared to the state‐of‐the‐art of the polymeric MWIR linear polarizers, the extinction ratio is improved by 1.4 times, and the transmission efficiency is increased by 2.5 times. Theoretical analysis with the multiple‐layer model based on the transfer matrix method predicts a matched transmission behavior with the experiment and a full‐wave electromagnetic simulation.}, number={5}, journal={Macromolecular Materials and Engineering}, publisher={Wiley}, author={Islam, Md Didarul and Kim, Jun Oh and Ko, Yeongun and Ku, Zahyun and Boyd, Darryl A. and Smith, Evan M. and Nguyen, Vinh Q. and Myers, Jason D. and Baker, Colin C. and Kim, Woohong and et al.}, year={2020}, month={Mar}, pages={2000033} }
 @article{walker_genzer_santiso_2020, title={Effect of Poly(vinyl butyral) Comonomer Sequence on Adhesion to Amorphous Silica: A Coarse-Grained Molecular Dynamics Study}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.0c10747}, abstractNote={Modulating a comonomer sequence, in addition to overall chemical composition, is the key to unlocking the true potential of many existing commercial copolymers. We employ coarse-grained molecular dynamics (MD) simulations to study the behavior of random-blocky poly(vinyl butyral-co-vinyl alcohol) (PVB) melts in contact with an amorphous silica surface, representing the interface found in laminated safety glass. Our two-pronged coarse-graining approach utilizes both macroscopic thermophysical data and all-atom molecular dynamics simulation data. Polymer-polymer nonbonded interactions are described by the fused-sphere SAFT-γ Mie equation of state, while bonded interactions are derived using Boltzmann inversion to match bond and angle distributions from all-atom PVB chains. Spatially-dependent polymer-surface interactions are mapped from a hydroxylated all-atom amorphous silica slab model and all-atom monomers to an external potential acting on the coarse-grained sites. We ran a series of interfacial coarse-grained MD simulations for PVB melts, systematically varying overall chemical composition and block length distribution. We discovered an unexpectedly complex relationship between blockiness parameter and adhesion energy. For intermediate vinyl alcohol (VA) content, adhesion strength to the silica slab was found to be maximal not for diblock copolymers, but rather random-blocky copolymers with a moderately high degree of blockiness. We attribute this to two main factors: (1) changes in morphology, which dramatically alter the number of VA beads interacting with the surface, and (2) a non-negligible contribution of vinyl butyral (VB) monomers to adhesion energy, due to their preference to adsorb to zones with low hydroxyl density on the silica surface.}, number={42}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Walker, Christopher C. and Genzer, Jan and Santiso, Erik E.}, year={2020}, month={Oct}, pages={47879–47890} }
 @article{islam_liu_boyd_zhong_nahid_henry_taussig_ko_nguyen_myers_et al._2020, title={Enhanced mid-wavelength infrared refractive index of organically modified chalcogenide (ORMOCHALC) polymer nanocomposites with thermomechanical stability}, volume={108}, ISSN={["1873-1252"]}, url={http://dx.doi.org/10.1016/j.optmat.2020.110197}, DOI={10.1016/j.optmat.2020.110197}, abstractNote={Abstract Organically modified chalcogenide (ORMOCHALC) polymers have proven to be alternatives to the conventional inorganic materials for mid-wavelength infrared (MWIR, λ = 3–5 μm) optical components. While the refractive index of ORMOCHALC can be reinforced by the content of chalcogenides such as sulfur (S) and selenium (Se), the increased portion of the S or Se deteriorate the thermomechanical stabilities. As a remedy, this study utilizes ZnS nanoparticles to reinforce both optical and thermomechanical properties of the sulfur-based ORMOCHALC polymer, poly(S-random-1,3-diisopropenylbenzene). The refractive index n and extinction coefficient k of the nanocomposites were characterized by Infrared Variable Angle Spectroscopic Ellipsometry (IR-VASE). The results show a significant increment in the refractive index of Δn = 6.58% at the wavelength of 4 μm by adding 20 wt% ZnS (or 7.29 vol%) in the ORMOCHALC polymer. The low extinction coefficient of the nanocomposites (}, journal={OPTICAL MATERIALS}, author={Islam, Md Didarul and Liu, Sipan and Boyd, Darryl A. and Zhong, Yaxu and Nahid, Masrur Morshed and Henry, Reece and Taussig, Laine and Ko, Yeongun and Nguyen, Vinh Q. and Myers, Jason D. and et al.}, year={2020}, month={Oct} }
 @article{walker_genzer_santiso_2020, title={Extending the fused-sphere SAFT-gamma Mie force field parameterization approach to poly(vinyl butyral) copolymers}, volume={152}, ISSN={["1089-7690"]}, DOI={10.1063/1.5126213}, abstractNote={SAFT-γ Mie, a molecular group-contribution equation of state with foundations in the statistical associating fluid theory framework, is a promising means for developing accurate and transferable coarse-grained force fields for complex polymer systems. We recently presented a new approach for incorporating bonded potentials derived from all-atom molecular dynamics simulations into fused-sphere SAFT-γ Mie homopolymer chains by means of a shape factor parameter, which allows for bond distances less than the tangent-sphere value required in conventional SAFT-γ Mie force fields. In this study, we explore the application of the fused-sphere SAFT-γ Mie approach to copolymers. In particular, we demonstrate its capabilities at modeling poly(vinyl alcohol-co-vinyl butyral) (PVB), an important commercial copolymer widely used as an interlayer in laminated safety glass applications. We found that shape factors determined from poly(vinyl alcohol) and poly(vinyl butyral) homopolymers do not in general correctly reproduce random copolymer densities when standard SAFT-γ Mie mixing rules are applied. However, shape factors optimized to reproduce the density of a random copolymer of intermediate composition resulted in a model that accurately represents density across a wide range of chemical compositions. Our PVB model reproduced copolymer glass transition temperature in agreement with experimental data, but heat capacity was underpredicted. Finally, we demonstrate that atomistic details may be inserted into equilibrated fused-sphere SAFT-γ Mie copolymer melts through a geometric reverse-mapping algorithm.}, number={4}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Walker, Christopher C. and Genzer, Jan and Santiso, Erik E.}, year={2020}, month={Jan} }
 @article{cutright_finkelstein_orlowski_mcintosh_brotherton_fabiani_khan_genzer_menegatti_2020, title={Nonwoven fiber mats with thermo-responsive permeability to inorganic and organic electrolytes}, volume={616}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2020.118439}, abstractNote={This study presents the development and characterization of nonwoven fiber mats (NWFs) with stimuli-controlled permeability. An ensemble of membranes was initially constructed by coating the fibers of polypropylene NWFs with a layer of poly ((N-isopropyl acrylamide)-co-(acrylic acid)) (PNIPAm-co-AA) hydrogel. Different coatings were produced by varying the PNIPAm/AA monomer ratio between 3.9 and 18.6. The thermo-responsive layer is expanded at room temperature and contracts when heated above its lower critical solution temperature (LCST). The resulting membranes were first characterized via laser scanning microscopy and fluorescence confocal microscopy to evaluate the thickness and morphology of the hydrogel layer. Microscopy shows uniform coating of the fibers, with a thickness comparable to the fiber diameter, and homogeneous filling of the pore space. The permeability of the NWFs was then evaluated using different solutes, namely an inorganic salt (sodium chloride), an organic acid (citric acid), and an amphiphilic drug (Doxorubicin). These tests consistently show that the flux of the solute is (1) higher at temperatures > LCST, where the hydrogel layer collapses and opens the pore space, and (2) decreases at room temperature (<LCST) in a composition-dependent manner (lower for hydrogels with higher AA content); and (3) the thermo-responsive change in permeability is fully reversible.}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Cutright, Camden and Finkelstein, Rachel and Orlowski, Elliot and McIntosh, Evan and Brotherton, Zach and Fabiani, Thomas and Khan, Saad and Genzer, Jan and Menegatti, Stefano}, year={2020}, month={Dec} }
 @article{abd-el-aziz_antonietti_barner-kowollik_binder_boeker_boyer_buchmeiser_cheng_d'agosto_floudas_et al._2020, title={The Next 100 Years of Polymer Science}, volume={221}, ISSN={["1521-3935"]}, DOI={10.1002/macp.202000216}, abstractNote={AbstractThe year 2020 marks the 100th anniversary of the first article on polymerization, published by Hermann Staudinger. It is Staudinger who realized that polymers consist of long chains of covalently linked building blocks. Polymers have had a tremendous impact on the society ever since this initial publication. People live in a world that is almost impossible to imagine without synthetic polymers. But what does the future hold for polymer science? In this article, the editors and advisory board of Macromolecular Chemistry and Physics reflect on this question.}, number={16}, journal={MACROMOLECULAR CHEMISTRY AND PHYSICS}, author={Abd-El-Aziz, Alaa S. and Antonietti, Markus and Barner-Kowollik, Christopher and Binder, Wolfgang H. and Boeker, Alexander and Boyer, Cyrille and Buchmeiser, Michael R. and Cheng, Stephen Z. D. and D'Agosto, Franck and Floudas, George and et al.}, year={2020}, month={Aug} }
 @article{turgman-cohen_geezer_2019, title={Computer Simulation of Surface-Initiated Controlled Radical Polymerization: Effect of Free-Monomer Model on Brush Properties}, volume={28}, ISSN={["1521-3919"]}, DOI={10.1002/mats.201900033}, abstractNote={AbstractMonte Carlo simulation is employed using the bond‐fluctuation model (BFM) to explore the role of free‐monomer model on surface‐initiated controlled polymerization from flat substrates. Three free‐monomer models differ in two aspects: 1) their extent of excluded volume interactions between free‐monomer/polymer segments and 2) monomer availability (finite or infinite) during the simulation. In the explicit monomer (EM) model, free‐monomers behave as a single BFM‑type units. In the phantom monomer (PM) model, free‐monomers act analogously to those in the EM model but lack excluded volume interactions with the growing polymers. In the implicit monomer (IM) model, no explicit monomers are included in the simulation box; the polymers can grow as long as space is available near active chain‐ends. It is found that the breadth of the molecular weight distribution of the grown polymers decreases from EM, to PM, to IM models. With the EM model, free‐monomers are excluded from the near‐surface region, while with the PM model they are not. Due to its excluded volume interactions, the EM model tends to compress the brush against the substrate. Finally, the relaxation of the shape of a polydisperse brush after the polymerization reaction ends has been reported.}, number={5}, journal={MACROMOLECULAR THEORY AND SIMULATIONS}, author={Turgman-Cohen, Salomon and Geezer, Jan}, year={2019}, month={Sep} }
 @article{miles_ko_genzer_2020, title={Dependence of deposition method on the molecular structure and stability of organosilanes revealed from degrafting by tetrabutylammonium fluoride}, volume={22}, ISSN={["1463-9084"]}, DOI={10.1039/c9cp05221f}, abstractNote={We probe the structure of self-assembled monolayers comprising organosilanes on flat silica-based surfaces prepared by liquid and vapor deposition by removing the organosilane molecules gradually from the substrate via tetrabutylammonium fluoride.}, number={2}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Miles, Jason and Ko, Yeongun and Genzer, Jan}, year={2020}, month={Jan}, pages={658–666} }
 @article{ko_miles_genzer_2019, title={Determining Water Sorption and Desorption in Thin Hydrophilic Polymer Films by Thermal Treatment}, volume={1}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.9b00607}, abstractNote={Knowledge of dry thickness of polymer films is required to determine the areal density of polymeric grafts and the degree of swelling of polymer networks and surface-anchored polymer assemblies. Because hydrophilic polymer films absorb water at ambient conditions and retain it, it is challenging to establish accurate dry thickness in such systems. Here we report on determining water uptake by chargeable/charged polymer films by monitoring the coefficient of thermal expansion (CTE) and thermo-optic coefficient (TOC) using ellipsometry. Knowing accurate amount of moisture in polymer films is needed for numerous applications, including, humidity and temperature sensors, polymer nanoreactors, lubricating coatings, antibacterial surfaces, and many others.}, number={9}, journal={ACS APPLIED POLYMER MATERIALS}, author={Ko, Yeongun and Miles, Jason R. and Genzer, Jan}, year={2019}, month={Sep}, pages={2495–2502} }
 @article{walker_genzer_santiso_2019, title={Development of a fused-sphere SAFT-gamma Mie force field for poly(vinyl alcohol) and poly(ethylene)}, volume={150}, ISSN={["1089-7690"]}, DOI={10.1063/1.5078742}, abstractNote={SAFT-γ Mie, a group-contribution equation of state rooted in Statistical Associating Fluid Theory, provides an efficient framework for developing accurate, transferable coarse-grained force fields for molecular simulation. Building on the success of SAFT-γ Mie force fields for small molecules, we address two key issues in extending the SAFT-γ Mie coarse-graining methodology to polymers: (1) the treatment of polymer chain rigidity and (2) the disparity between the structure of linear chains of tangent spheres and the structure of the real polymers. We use Boltzmann inversion to derive effective bond-stretching and angle-bending potentials mapped from all-atom oligomer molecular dynamics (MD) simulations to the coarse-grained sites and a fused-sphere version of SAFT-γ Mie as the basis for non-bonded interactions. The introduction of an overlap parameter between Mie spheres leads to a degeneracy when fitting to monomer vapor-liquid equilibria (VLE) data, which we resolve by matching polymer density from coarse-grained MD simulation with that from all-atom simulation. The result is a chain of monomers rigorously parameterized to experimental VLE data and with structural detail consistent with all-atom simulations. We test our approach on atactic poly(vinyl alcohol) and polyethylene and compare the results for SAFT-γ Mie models with structural detail mapped from the Optimized Potentials for Liquid Simulations (OPLS) and Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) all-atom force fields.}, number={3}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Walker, Christopher C. and Genzer, Jan and Santiso, Erik E.}, year={2019}, month={Jan} }
 @article{walker_pandiyarajan_efimenko_genzer_2019, title={Generating Surface-Anchored Zwitterionic Networks and Studying Their Resistance to Bovine Serum Albumin Adsorption}, volume={1}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.9b00772}, abstractNote={We report a simple method to generate surface-anchored zwitterionic network coatings that exhibit low nonspecific protein adsorption. We first synthesize amphiphilic random copolymers comprising 2-(dimethylamino)ethyl methacrylate (DMAEMA) and propargyl methacrylate (PGMA) units in two different nominal molar ratios (50:50 and 75:25) by free radical copolymerization. The DMAEMA moieties in the copolymers are then betainized with 1,3-propane sultone to obtain zwitterionic macromolecules. We create substrate-anchored network coatings by casting thin copolymer films (∼100 nm) containing 2 wt % of photoactive benzophenone onto a polystyrene substrate and cross-link them by UV-light irradiation at 365 nm (UV dose = 9–10 J/cm2). We investigate the cross-linking reaction with infrared spectroscopy, monitor the change in film thickness, and study the swelling behavior of the coatings as a function of ionic strength and electrolyte using spectroscopic ellipsometry. We demonstrate the performance of such surface-at...}, number={12}, journal={ACS APPLIED POLYMER MATERIALS}, author={Walker, Edwin J., Jr. and Pandiyarajan, C. K. and Efimenko, Kirill and Genzer, Jan}, year={2019}, month={Dec}, pages={3323–3333} }
 @article{hubbard_cui_huang_takahashi_dickey_genzer_king_gong_2019, title={Hydrogel/Elastomer Laminates Bonded via Fabric Interphases for Stimuli-Responsive Actuators}, volume={1}, ISSN={["2590-2385"]}, DOI={10.1016/j.matt.2019.04.008}, abstractNote={The human body is composed of composite structures made of water-rich hydrophilic domains and hydrophobic barriers. Combining hydrogels with elastomers results in similar synthetic biomaterials applicable to fields ranging from stretchable electronics to actuators. Here, we report a method to combine hydrogels with elastomers via a glass fiber fabric interphase. The interphase plays two roles: it enables chemically different materials to be robustly bound without chemical treatment while also dramatically improving the mechanical properties of the composite. Maximum interfacial adhesion energies of ∼1,000 N m−1 between the hydrogel and fabric and ∼360 N m−1 between the elastomer and fabric approach adhesion values of chemically bound soft materials. The composite tearing toughness (143 kJ m−2) vastly exceeds that of all neat components. In these materials, Young's modulus is high (∼1.2 GPa), while bending modulus is low (∼7 MPa), resulting in structures that can serve as actuators through controlled solvent exposure.}, number={3}, journal={MATTER}, author={Hubbard, Amber M. and Cui, Wei and Huang, Yiwan and Takahashi, Riku and Dickey, Michael D. and Genzer, Jan and King, Daniel R. and Gong, Jian Ping}, year={2019}, month={Sep}, pages={674–689} }
 @article{erramilli_genzer_2019, title={Influence of surface topography attributes on settlement and adhesion of natural and synthetic species}, volume={15}, ISSN={["1744-6848"]}, DOI={10.1039/c9sm00527g}, abstractNote={Surface topographies of various sizes, shapes, and spatial organization abound in nature.}, number={20}, journal={SOFT MATTER}, author={Erramilli, Shreya and Genzer, Jan}, year={2019}, month={May}, pages={4045–4067} }
 @article{kopyshev_kanevche_lomadze_pfitzner_loebner_patil_genzer_heberle_santer_2019, title={Light-Induced Structuring of Photosensitive Polymer Brushes}, volume={1}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.9b00705}, abstractNote={We investigate light-induced irreversible structuring of surface topographies in poly(3-sulfopropyl methacrylate/potassium salt) (PSPMK) brushes on flat solid substrates prepared by surface-initiated atom transfer radical polymerization. The brushes have been loaded with azobenzene-based surfactant comprised of positively charged headgroups and hydrophobic tail. The surfactant exhibits photoresponsive properties through photoisomerization from the trans to cis states leading to significant changes in physicochemical properties of grafted polymer chains. The azobenzene surfactant enables photoresponsive behavior without introducing irreversible changes to chemical composition of the parent polymer brush. Exposing these photosensitive brushes to irradiation with UV interference beams causes the polymer brush to form surface relief grating (SRG) patterns. The cationic surfactant penetrates only ∼25% of the upper portion of the PSPMK brush, resulting in the formation of two sections within the brush: a photor...}, number={11}, journal={ACS APPLIED POLYMER MATERIALS}, author={Kopyshev, Alexey and Kanevche, Katerina and Lomadze, Nino and Pfitzner, Emanuel and Loebner, Sarah and Patil, Rohan R. and Genzer, Jan and Heberle, Joachim and Santer, Svetlana}, year={2019}, month={Nov}, pages={301–3026} }
 @article{ma_lin_kim_ko_kim_oh_sun_gorman_voinov_smirnov_et al._2019, title={Liquid Metal Nanoparticles as Initiators for Radical Polymerization of Vinyl Monomers}, volume={8}, ISSN={["2161-1653"]}, url={https://doi.org/10.1021/acsmacrolett.9b00783}, DOI={10.1021/acsmacrolett.9b00783}, abstractNote={Sonication of gallium or gallium-based liquid metals in an aqueous solution of vinyl monomers leads to rapid free radical polymerization (FRP), without the need for conventional molecular initiators. Under ambient conditions, a passivating native oxide separates these metals from solution and renders the metal effectively inert. However, sonication generates liquid metal nanoparticles (LMNPs) of ∼100 nm diameter and thereby increases the surface area of the metal. The exposed metal initiates polymerization, which proceeds via a FRP mechanism and yields high molecular weight polymers that can form physical gels. Spin trapping EPR reveals the generation of free radicals. Time-of-flight secondary ion mass spectrometry measurements confirm direct polymer bonding to gallium, verifying the formation of surface-anchored polymer grafts. The grafted polymers can modify the interfacial properties, that is, the preference of the metal particles to disperse in aqueous versus organic phases. The polymer can also be degrafted and isolated from the particles using strong acid or base. The concept of physically disrupting passivated metal surfaces offers new routes for surface-initiated polymerization and has implications for surface modification, reduction reactions, and fabrication of mechanically responsive materials.}, number={11}, journal={ACS MACRO LETTERS}, publisher={American Chemical Society (ACS)}, author={Ma, Jinwoo and Lin, Yiliang and Kim, Yong-Woo and Ko, Yeongun and Kim, Jongbeom and Oh, Kyu Hwan and Sun, Jeong-Yun and Gorman, Christopher B. and Voinov, Maxim A. and Smirnov, Alex I. and et al.}, year={2019}, month={Nov}, pages={1522–1527} }
 @article{li_lin_dai_ko_genzer_2019, title={Mechanochemical Degrafting of a Surface-Tethered Poly(acrylic acid) Brush Promoted Etching of Its Underlying Silicon Substrate}, volume={35}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.9b02610}, abstractNote={The stability of surface-tethered polyelectrolyte brushes has been investigated during the past few years. We have previously reported on degrafting of poly(acrylic acid) (PAA) polymer brushes from flat silicone substrates. Here we present detailed study on the effects of NaCl concentration and the grafting density and molecular weight on the stability of PAA brushes during incubation in 0.1 M ethanolamine buffer (pH 9.0) solutions. Without NaCl in the buffer solution, the PAA brushes remain intact. Adding NaCl facilitates etching of the substrate due to accelerating dissolution of the top silica layer and promoting degrafting of the PAA chains. The PAA grafting density and molecular weight play an important role in substrate etching by affecting the penetration barrier and local concentration of the etchants. We also tested the stability of self-assembled monolayers (SAMs) made of hydrophobic alkyltrichlorosilanes anchored on silicon substrates. The results demonstrated that the SAMs were too thin to protect the substrates from etching, in contrast to thick poly(methyl methacrylate) (PMMA) brushes. Our findings suggest that both polymer brushes (especially polyelectrolyte brushes) and SAMs anchored to silicon substrates may undergo erosion/etching on the substrates in basic environments, which compromises their stability and therefore jeopardizes their applications in coating, biosensing, etc.}, number={42}, journal={LANGMUIR}, author={Li, Yuanchao and Lin, Yiliang and Dai, Yunkai and Ko, Yeongun and Genzer, Jan}, year={2019}, month={Oct}, pages={13693–13699} }
 @article{cutright_brotherton_alexander_harris_shi_khan_genzer_menegatti_2020, title={Packing density, homogeneity, and regularity: Quantitative correlations between topology and thermoresponsive morphology of PNIPAM-co-PAA microgel coatings}, volume={508}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2019.145129}, abstractNote={This study investigates the formation of monolayers of microgel particles comprising poly[(N-isopropylacrylamide)-co-(acrylic acid)] on solid substrates, their surface morphology, and stimuli-responsiveness. Crosslinked microgels with different chemical composition were produced to show a broad range of responses in hydrodynamic radius and degree of self-assembly with temperature and pH. Microgels were deposited on silicon wafers primed with a bilayer of poly(octadecene-alt-maleic anhydride) and polyethyleneimine by either incubation or spin coating of aqueous suspension of microgels at different temperature and pH. The characterization of the microgel-coated wafers led to the identification of three metrics describing microgel arrangement: density (ρ); heterogeneity (H), which correlates strongly with ρ and depends on deposition temperature and pH with statistical significance, but not on microgel composition; and packing efficiency (PE), which portrays the regularity of microgel arrangement and exhibits no correlation with ρ nor H. The values of ρ, H, and PE calculated for in silico models of microgel coatings confirmed that these three metrics portray distinct characteristics of surface topology. Finally, profilometry analysis showed that microgel coatings respond to thermal stimuli with sensible variations in surface roughness; notably, the thermal variation of roughness correlates strongly with ρ and H, and to a lesser extent with PE.}, journal={APPLIED SURFACE SCIENCE}, author={Cutright, Camden and Brotherton, Zach and Alexander, Landon and Harris, Jacob and Shi, Kaihang and Khan, Saad and Genzer, Jan and Menegatti, Stefano}, year={2020}, month={Apr} }
 @article{ko_genzer_2019, title={Spontaneous Degrafting of Weak and Strong Polycationic Brushes in Aqueous Buffer Solutions}, volume={52}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.9b01362}, abstractNote={Polymers grafted to substrates have traditionally been considered stable because of the covalent bonds that hold the polymers attached to the substrate. However, several recent reports have indicated that grafted polymers may detach from substrates under specific conditions. In this work, we report on a systematic study of polymer degrafting involving polycationic brushes with different degrees of quaternization (DQ, mol %), which have been incubated in three different buffer solutions (pH 4, 7.4, and 9) with the same ionic strength of 0.05 M. We have varied the molecular weight (MW) and grafting density (σ) of the polymer brushes using a combinatorial setup to examine the effect of MW, σ, and DQ on polymer degrafting. Furthermore, we explored the effect of the bonding environment at the base of the initiator (mono- vs. tri-functional) of the grafted polymer layer at the substrate on the overall stability of polymer brushes on the substrate. The two major findings in this paper are (1) degrafting of polyc...}, number={16}, journal={MACROMOLECULES}, author={Ko, Yeongun and Genzer, Jan}, year={2019}, month={Aug}, pages={6192–6200} }
 @article{pandiyarajan_genzer_2019, title={Thermally Activated One-Pot, Simultaneous Radical and Condensation Reactions Generate Surface-Anchored Network Layers from Common Polymers}, volume={52}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.8b02194}, abstractNote={We present a versatile one-pot synthesis method that generates surface-attached polymer networks by cross-linking common polymers using thermally active 6-azidosulfonylhexyltriethoxysilane (6-ASHTES), which acts as a cross-linker and a surface-anchoring agent. We deposit a thin layer (∼200 nm) of a mixture comprising a given amount of 6-ASHTES and a polymer onto the substrate and anneal it at elevated temperatures (100–140 °C). Upon heating, the sulfonyl azide groups release nitrogen, and the resulting nitrenes abstract protons from the neighboring C–H bonds in polymers and undergo a C–H insertion reaction and/or recombination to form sulfonamide bonds. Condensation among ethoxysilane headgroups in bulk links 6-ASHTES units completes cross-linking. Simultaneously, 6-ASHTES reacts with substrate-bound −OH or C–H groups and attaches the covalently cross-linked polymer to the substrate. We carry out systematic investigation of gel kinetics involving annealing temperature, annealing time, and the concentratio...}, number={2}, journal={MACROMOLECULES}, author={Pandiyarajan, C. K. and Genzer, Jan}, year={2019}, month={Jan}, pages={700–707} }
 @article{datta_efimenko_genzer_2019, title={Thermally driven directional free-radical polymerization in confined channels}, volume={10}, ISSN={["1759-9962"]}, url={https://doi.org/10.1039/C8PY01550C}, DOI={10.1039/c8py01550c}, abstractNote={We report on the formation of poly(acrylamide) (PAAm) with a relatively-narrow molecular weight distribution (MWD) by means of thermally-driven directional free-radical polymerization carried out in polymerization chambers featuring two parallel glass walls separated by various distances, ranging from sub-millimeter to a few millimeters.}, number={8}, journal={POLYMER CHEMISTRY}, publisher={Royal Society of Chemistry (RSC)}, author={Datta, Preeta and Efimenko, Kirill and Genzer, Jan}, year={2019}, month={Feb}, pages={920–925} }
 @article{mailen_wagner_bang_zikry_dickey_genzer_2019, title={Thermo-mechanical transformation of shape memory polymers from initially flat discs to bowls and saddles}, volume={28}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85065648786&partnerID=MN8TOARS}, DOI={10.1088/1361-665X/ab030a}, abstractNote={This paper describes the transformation of shape memory polymer (SMP) discs, from flat sheets to complex three-dimensional (3D) shapes, in response to heat generated by localized absorption of external infrared (IR) light. The gray-scale ink darkness printed on the surface of the SMP sheet determines the amount of absorbed light and the amount of heat generated on the surface of the sheet. Consequently, the lateral pattern of the ink governs the out-of-plane deformation of the SMP sheets due to variations in localized heating and shrinking. While recent studies have focused primarily on out-of-plane deformations of planar, rectangular substrates printed with linear patterns of ink and featuring either discrete or gradient ink variation, only limited studies have been performed on circular substrates with axisymmetric ink patterns. When heated by IR light, the axial symmetry of these ink designs produces unique out-of-plane deformations of the sheets, such as saddle shapes or bowl-like structures. We investigate these designs by utilizing a finite element analysis of material shrinkage and deformation, and we validate the model with experimental measurements and observations. This investigation provides insights into the mechanisms that cause axisymmetric geometries and ink patterns to form non-axisymmetric 3D structures, which can lead to the ability to program planar geometries that form complex 3D shapes when exposed to external stimuli.}, number={4}, journal={SMART MATERIALS AND STRUCTURES}, author={Mailen, Russell W. and Wagner, Catherine H. and Bang, Rachel S. and Zikry, Mohammed and Dickey, Michael D. and Genzer, Jan}, year={2019}, month={Apr} }
 @article{cooper_joshipura_parekh_norkett_mailen_miller_genzer_dickey_2019, title={Toughening stretchable fibers via serial fracturing of a metallic core}, volume={5}, ISSN={["2375-2548"]}, url={https://doi.org/10.1126/sciadv.aat4600}, DOI={10.1126/sciadv.aat4600}, abstractNote={Stretchable fibers dissipate energy via the sequential fracturing of a metallic core held together by an elastomeric shell.}, number={2}, journal={SCIENCE ADVANCES}, publisher={American Association for the Advancement of Science (AAAS)}, author={Cooper, Christopher B. and Joshipura, Ishan D. and Parekh, Dishit P. and Norkett, Justin and Mailen, Russell and Miller, Victoria M. and Genzer, Jan and Dickey, Michael D.}, year={2019}, month={Feb} }
 @article{jelken_pandiyarajan_genzer_lomadze_santer_2018, title={Fabrication of Flexible Hydrogel Sheets Featuring Periodically Spaced Circular Holes with Continuously Adjustable Size in Real Time}, volume={10}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.8b09580}, abstractNote={We report on the formation of stimuli-responsive structured hydrogel thin films whose pattern geometry can be adjusted on demand and tuned reversibly by varying solvent quality or by changing temperature. The hydrogel films, ∼100 nm in thickness, were prepared by depositing layers of random copolymers comprising N-isopropylacrylamide and ultraviolet (UV)-active methacryloyloxybenzophenone units onto solid substrates. A two-beam interference pattern technique was used to cross-link the selected areas of the film; any unreacted material was extracted using ethanol after UV light-assisted cross-linking. In this way, we produced nanoholes, perfectly ordered structures with a narrow size distribution, negligible tortuosity, adjustable periodicity, and a high density. The diameter of the circular holes ranged from a few micrometers down to several tens of nanometers; the hole periodicity could be adjusted readily by changing the optical period of the UV interference pattern. The holes were reversibly closed and opened by swelling/deswelling the polymer networks in the presence of ethanol and water, respectively, at various temperatures. The reversible regulation of the hole diameter can be repeated many times within a few seconds. The hydrogel sheet with circular holes periodically arranged may also be transferred onto different substrates and be employed as tunable templates for the deposition of desired substances.}, number={36}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Jelken, Joachim and Pandiyarajan, C. K. and Genzer, Jan and Lomadze, Nino and Santer, Svetlana}, year={2018}, month={Sep}, pages={30844–30851} }
 @article{patil_miles_ko_datta_rao_kiserow_genzer_2018, title={Kinetic Study of Degrafting Poly(methyl methacrylate) Brushes from Flat Substrates by Tetrabutylammonium Fluoride}, volume={51}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.8b01832}, abstractNote={Polymer degrafting is a process in which surface-attached polymer brushes are removed from the substrate by breaking a chemical bond in proximity to the substrate. This paper provides insight into the kinetics of degrafting poly(methyl methacrylate) (PMMA) brushes using tetrabutylammonium fluoride (TBAF) and demonstrates how the process can be modeled using a series of degrafting reactions. The trichlorosilane-based polymerization initiator utilized here to synthesize PMMA grafts by surface-initiated atom transfer radical polymerization anchors to the silica substrate by up to three potential attachment points. During the degrafting sequence this anchoring reduces to two and one chemical bond and finally results in complete liberation of the PMMA macromolecule from the substrate. We investigate the effect of TBAF concentration, the initial grafting density of PMMA grafts on the substrate, and TBAF exposure time on degrafting of PMMA by monitoring the instantaneous areal grafting density of PMMA on the sub...}, number={24}, journal={MACROMOLECULES}, author={Patil, Rohan and Miles, Jason and Ko, Yeongun and Datta, Preeta and Rao, Balaji M. and Kiserow, Douglas and Genzer, Jan}, year={2018}, month={Dec}, pages={10237–10245} }
 @article{bennett_kristof_vasudevan_genzer_srogl_abolhasani_2018, title={Microfluidic synthesis of elastomeric microparticles: A case study in catalysis of palladium-mediated cross-coupling}, volume={64}, ISSN={0001-1541}, url={http://dx.doi.org/10.1002/AIC.16119}, DOI={10.1002/AIC.16119}, abstractNote={Palladium (Pd)‐loaded poly‐hydromethylsiloxane (PHMS) microparticles of tunable size and elasticity are prepared in a capillary‐based coaxial flow‐focusing microfluidic device constructed using off‐the‐shelf components. Simultaneous droplet formation and chemical cross‐linking processes are performed by tuning the dilution of the cross‐linking catalyst in the annular flow of the microreactor, resulting in PHMS microparticles synthesized in a single step. The size of the elastomeric microparticles can be tuned by adjusting the flow rate ratio of the polymer and cross‐linker mixture to water, while the elasticity can be tuned by the polymer to cross‐linker ratio as well as the flow rate ratio of the polymer mixture to cross‐linking catalyst mixture. Microparticle elasticity is characterized by the degree of solvent uptake. Application of the synthesized PHMS microparticles in organic synthesis is demonstrated by producing monodispersed Pd‐loaded microparticles and utilizing them as microreaction vessels for continuous Suzuki‐Miyaura cross‐coupling in a Pd‐loaded microparticle‐packed bed reactor. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3188–3197, 2018}, number={8}, journal={AIChE Journal}, publisher={Wiley}, author={Bennett, Jeffrey A. and Kristof, Andrew J. and Vasudevan, Vishal and Genzer, Jan and Srogl, Jiri and Abolhasani, Milad}, year={2018}, month={Feb}, pages={3188–3197} }
 @article{hubbard_davis_dickey_genzer_2018, title={Shape memory polymers for self-folding via compression of thermoplastic sheets}, volume={135}, ISSN={["1097-4628"]}, url={https://doi.org/10.1002/app.46889}, DOI={10.1002/app.46889}, abstractNote={ABSTRACTWe report a simple method to strain, and thereby program, shape memory polymers by compressing planar thermoplastic sheets. This work is motivated by the limited number of commercially available prestrained polymer sheets; current examples include: Shrinky Dinks, Eastman's Embrace, and polyurethane shrink films. However, these commercial specimens limit the sample thickness, polymer composition, and amount of stored strain. We show here that melt pressing can strain thermoplastic sheets over a range of thicknesses and polymer chemical compositions. After pressing (and thus, straining), the polymer sheets can self‐fold out‐of‐plane into complex geometries using two different actuation mechanisms, both of which locally release strain stored in the polymer. Three‐dimensional geometries are attained experimentally with both thick (~12 mm) and thin (~1 mm) strained polymer samples with a range of polymer compositions. Digital image correlation maps the strain profile within the melt pressed samples while a Mooney–Rivlin and geometric model predicts the average strain and folding response of the samples, respectively. The model predictions agree well with experimental results. These findings enable self‐folding with a broader design space such as polymer chemical composition, sample thickness, strain within the sample, and external stimulus. Techniques presented here should translate to other thermoplastic polymers, thus making this technique a viable tool to increase the available pool of materials available for self‐folding devices. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46889.}, number={47}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, publisher={Wiley}, author={Hubbard, Amber M. and Davis, Duncan S. and Dickey, Michael D. and Genzer, Jan}, year={2018}, month={Dec} }
 @article{lin_genzer_li_qiao_dickey_tang_2018, title={Sonication-enabled rapid production of stable liquid metal nanoparticles grafted with poly(1-octadecene-alt-maleic anhydride) in aqueous solutions}, volume={10}, ISSN={["2040-3372"]}, url={https://doi.org/10.1039/C8NR05600E}, DOI={10.1039/c8nr05600e}, abstractNote={We demonstrate sonication-enabled production of liquid metal nanoparticles grafted with poly(1-octadecene-alt-maleic anhydride) in water that remain stable in biological buffers.}, number={42}, journal={NANOSCALE}, publisher={Royal Society of Chemistry (RSC)}, author={Lin, Yiliang and Genzer, Jan and Li, Weihua and Qiao, Ruirui and Dickey, Michael D. and Tang, Shi-Yang}, year={2018}, month={Nov}, pages={19871–19878} }
 @inproceedings{michel_felder_genzer_fuller_2000, title={Student use of instructional technology in the introductory chemical engineering course}, DOI={10.18260/1-2--28492}, abstractNote={An introductory computer engineering course where students learn about combinational and sequential circuits is fundamental to any Electrical and Computer Engineering (ECE) curriculum. Many of these courses are taught using a hardware description language (HDL) such as Verilog or VHDL. However, younger students traditionally struggle with HDLs due to their abstract nature. The students are used to designing with traditional logic gates and structures, but are often confused by the software-like interface that an HDL provides. This creates a disconnection between the student's experience in the classroom where the students learn with one method (visually with gates and structures) and in labs or projects where they are asked to implement designs using text descriptors. Often times a student's frustration with HDLs leads to them being disinterested in digital systems or even computer engineering as a major. This paper will describe the transition of an introductory Computer Engineering course from primarily using Verilog for its assignments to instead using a combination of schematic capture (which is very similar to what they see in class) and Verilog. With this course's redesign, the author saw the student's self-reported confidence in their design skills improve by 44% (from 41% to 85%) and their interest in taking additional computer engineering courses improve by 10% (from 66% to 76%).}, booktitle={2000 ASEE Annual Conference Proceedings, ASEE, June 2000}, publisher={Washington, D.C.: American Society for Engineering Education}, author={Michel, A. and Felder, R.M. and Genzer, Jan and Fuller, H.}, year={2000} }
 @article{li_lin_ko_kiserow_genzer_2018, title={Visualization of Mechanochemically-Assisted Degrafting of Surface-Tethered Poly(Acrylic Acid) Brushes}, volume={7}, ISSN={["2161-1653"]}, DOI={10.1021/acsmacrolett.8b00241}, abstractNote={We report visualization of mechanochemically assisted degrafting of surface-tethered poly(acrylic acid) (PAA) brushes in a basic aqueous buffer at nanometer to micrometer length scale by monitoring changes in local etching of silicon substrates. PAA brushes were prepared by surface-initiated atom transfer radical polymerization and incubated in 0.1 M ethanolamine buffer (pH 9.0) with 0.5 M NaCl. Morphological changes of the underlying substrates were monitored by scanning electron microscopy and atomic force microscopy. The appearance of regular-shaped pits indicated etching of the substrate, and both their number and size grew with increasing incubation time. We compared the etching behaviors for PAA, poly(methyl methacrylate) (PMMA), and poly(poly(ethylene glycol) methacrylate) (PPEGMA) brushes grafted on silicon substrates. After incubation for 7 days, the substrate of PMMA brush remained intact. In PAA brush systems, we detected the formation of a few large pits whose size grew in time. Many pits showed up on the substrate of PPEGMA brush but with substantially smaller size compared to PAA. Our findings suggest that hydrophobicity and stability of the grafted polymers play an important role in the morphological changes of the underlying silicon substrates under given incubation conditions.}, number={6}, journal={ACS MACRO LETTERS}, author={Li, Yuanchao and Lin, Yiliang and Ko, Yeongun and Kiserow, Douglas and Genzer, Jan}, year={2018}, month={Jun}, pages={609–613} }
 @article{mailen_dickey_genzer_zikry_2017, title={A fully coupled thermo-viscoelastic finite element model for self-folding shape memory polymer sheets}, volume={55}, ISSN={["1099-0488"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85019544264&partnerID=MN8TOARS}, DOI={10.1002/polb.24372}, abstractNote={ABSTRACTThe thermo‐mechanical response of heat activated shape memory polymers (SMPs) has been investigated using a thermo‐viscoelastic finite element analysis that accounts for external and internal heat sources. SMPs can be thermally stimulated by external heat sources, such as temperature and surface heat flux, or from internal viscous heating. Viscous heating can significantly affect the response of SMP sheets by increasing the temperature during pre‐strain, which accelerates stress relaxation. This stress relaxation results in a slower shrinking rate when the SMP is reheated. Viscous heating also causes an increase in temperatures during unconstrained recovery. The predicted results elucidate how the coupled thermo‐mechanical loading conditions affect folding and unfolding of SMP sheets in response to localized heating in a hinged region. A parametric study of sheet thickness, hinge width, degree of pre‐strain, and hinge surface temperature is also conducted. The validated results can provide guidelines for the design of functional, self‐folding structures. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1207–1219}, number={16}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, publisher={Wiley}, author={Mailen, Russell W. and Dickey, Michael D. and Genzer, Jan and Zikry, Mohammed A.}, year={2017}, month={Aug}, pages={1207–1219} }
 @article{schoch_genzer_2018, title={Adsorption of size-polydisperse particles on sinusoidally corrugated surfaces}, volume={44}, ISSN={["1029-0435"]}, DOI={10.1080/08927022.2017.1405161}, abstractNote={Abstract We use adhesion model based on Monte Carlo computer simulation to study adsorption of core-shell spherical particles of polydisperse sizes onto sinusoidally corrugated substrates with predefined amplitude (A) and wavelength (λ). The core-shell particles comprise a hard inner core and an adhesive shell that mediates interaction with the substrate lattice elements. The probability distribution of particle sizes (diameters) is determined by either a single normal distribution function (Dmean = 20) of standard deviation 0–8 (0–40% of Dmean) or a bimodal distribution function constructed by adding two normal distributions of differing mean values. Using comparisons of these surface textures to flat substrates the surface texture reduces adhesion strength by up to ~40% for feature height 20 at λ/Dmean = 0.5 depending on the standard deviation. In systems featuring bimodal particle size distributions we observe that for mean particle size ratio (Dmean B/Dmean A) of 2 surface texture continues to reduce the adhesion strength of particles by ~40–50% for some combinations of A and λ when compared to flat analogues. However, at mean particle size ratio of 4, the surfaces tested no longer reduce particle adsorption significantly. This suggests that when particle sizes are far apart a second texture is needed to act against the smaller particles.}, number={6}, journal={MOLECULAR SIMULATION}, author={Schoch, Phillip K. and Genzer, Jan}, year={2018}, pages={494–506} }
 @article{hubbard_mailen_zikry_dickey_genzer_2017, title={Controllable curvature from planar polymer sheets in response to light}, volume={13}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/C7SM00088J}, DOI={10.1039/C7SM00088J}, abstractNote={The ability to change shape and control curvature in 3D structures starting from planar sheets can aid in assembly and add functionality to an object. Herein, we convert planar sheets of shape memory polymers (SMPs) into 3D objects with controllable curvature by dictating where the sheets shrink. Ink patterned on the surface of the sheet absorbs infrared (IR) light, resulting in localized heating, and the material shrinks locally wherever the temperature exceeds the activation temperature, Ta. We introduce two different mechanisms for controlling curvature within SMP sheets. The 'direct' mechanism uses localized shrinkage to induce curvature only in regions patterned with ink. The 'indirect' mechanism uses localized shrinkage in regions patterned with ink to induce curvature in neighboring regions without ink through a balance of internal stresses. Finite element analysis predicts the final shape of the polymer sheets with excellent qualitative agreement with experimental studies. Results from this study show that curvature can be controlled by the distribution and darkness of the ink pattern on the polymer sheet. Additionally, we utilize the direct and indirect curvature mechanisms to demonstrate the formation and actuation of gripper devices, which represent the potential utility of this approach.}, number={12}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Hubbard, Amber M. and Mailen, Russell W. and Zikry, Mohammed A. and Dickey, Michael D. and Genzer, Jan}, year={2017}, pages={2299–2308} }
 @article{miles_schlenker_ko_patil_rao_genzer_2017, title={Design and Fabrication of Wettability Gradients with Tunable Profiles through Degrafting Organosilane Layers from Silica Surfaces by Tetrabutylammonium Fluoride}, volume={33}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.7b02961}, abstractNote={Surface-bound wettability gradients allow for a high-throughput approach to evaluate surface interactions for many biological and chemical processes. Here we describe the fabrication of surface wettability gradients on flat surfaces by a simple, two-step procedure that permits precise tuning of the gradient profile. This process involves the deposition of homogeneous silane SAMs followed by the formation of a surface coverage gradient through the selective removal of silanes from the substrate. Removal of silanes from the surface is achieved by using tetrabutylammonium fluoride which selectively cleaves the Si-O bonds at the headgroup of the silane. The kinetics of degrafting has been modeled by using a series of first order rate equations, based on the number of attachment points broken to remove a silane from the surface. Degrafting of monofunctional silanes exhibits a single exponential decay in surface coverage; however, there is a delay in degrafting of trifunctional silanes due to the presence of multiple attachment points. The effects of degrafting temperature and time are examined in detail and demonstrate the ability to reliably and precisely control the gradient profile on the surface. We observe a relatively homogeneous coverage of silane (i.e., without the presence of islands or holes) throughout the degrafting process, providing a much more uniform surface when compared to additive approaches of gradient formation. Linear gradients were formed on the substrates to demonstrate the reproducibility and tuneability of this subtractive approach.}, number={51}, journal={LANGMUIR}, author={Miles, Jason and Schlenker, Spencer and Ko, Yeongun and Patil, Rohan and Rao, Balaji M. and Genzer, Jan}, year={2017}, month={Dec}, pages={14556–14564} }
 @article{pandiyarajan_genzer_2017, title={Effect of Network Density in Surface-Anchored Poly(N-isopropylacrylamide) Hydrogels on Adsorption of Fibrinogen}, volume={33}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.6b04434}, abstractNote={We describe a simple approach to generate surface-attached biocompatible hydrogels with tunable cross-link density and employ them to study the effect of gel structure on protein adsorption. Using free-radical polymerization, we synthesize a series of random copolymers comprising N-isopropylacrylamide (NIPAm) and the photoactive curing agent 4-methacryloyl-oxy-benzophenone (MABP) of mole fractions ranging from 2.5 to 10%. We deposit a thin film of the precursor copolymer (∼150 nm) on a silicon or glass substrate, which is precoated with monolayers of benzophenone-silane, then cross-link it through UV irradiation at 365 nm (dose ≈ 6-10 J/cm2) to generate surface-attached networks. A systematic investigation of the network properties such as gel fraction, cross-link density, and swelling ratio reveals that gels with higher MABP content (≥5%) produce densely cross-linked hydrophobic networks with low or no swelling in an aqueous medium. We study the adsorption of fibrinogen (Fg) on such hydrogel substrates and establish that the amount of adsorbed Fg depends on the degree of cross-linking and the swelling capacity of the networks. Specifically, although Fg adsorbs heavily on denser networks, loosely bound gels that swell in aqueous medium repel proteins. We attribute the latter behavior to entropic shielding and size-exclusion factors.}, number={8}, journal={LANGMUIR}, author={Pandiyarajan, C. K. and Genzer, Jan}, year={2017}, month={Feb}, pages={1974–1983} }
 @article{mailen_dickey_genzer_zikry_2017, title={Effects of thermo-mechanical behavior and hinge geometry on folding response of shape memory polymer sheets}, volume={122}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/1.5000040}, DOI={10.1063/1.5000040}, abstractNote={Shape memory polymer (SMP) sheets patterned with black ink hinges change shape in response to external stimuli, such as absorbed thermal energy from an infrared (IR) light. The geometry of these hinges, including size, orientation, and location, and the applied thermal loads significantly influence the final folded shape of the sheet, but these variables have not been fully investigated. We perform a systematic study on SMP sheets to fundamentally understand the effects of single and double hinge geometries, hinge orientation and spacing, initial temperature, heat flux intensity, and pattern width on the folding behavior. We have developed thermo-viscoelastic finite element models to characterize and quantify the stresses, strains, and temperatures as they relate to SMP shape changes. Our predictions indicate that hinge orientation can be used to reduce the total bending angle, which is the angle traversed by the folding face of the sheet. Two parallel hinges increase the total bending angle, and heat conduction between the hinges affects the transient folding response. IR intensity and initial temperatures can also influence the transient folding behavior. These results can provide guidelines to optimize the transient folding response and the three-dimensional folded structure obtained from self-folding polymer origami sheets that can be applied for myriad applications.}, number={19}, journal={JOURNAL OF APPLIED PHYSICS}, publisher={AIP Publishing}, author={Mailen, Russell W. and Dickey, Michael D. and Genzer, Jan and Zikry, Mohammed}, year={2017}, month={Nov} }
 @article{li_ko_lin_kiserow_genzer_2017, title={Enhanced Stability of Surface-Tethered Diblock Copolymer Brushes with a Neutral Polymer Block and a Weak Polyelectrolyte Block: Effects of Molecular Weight and Hydrophobicity of the Neutral Block}, volume={50}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.7b01825}, abstractNote={We study the stability of diblock copolymer brushes featuring a bottom neutral block, poly(methyl methacrylate) (PMMA) or poly(poly(ethylene glycol) methacrylate) (PPEGMA), and a top poly(acrylic acid) (PAA) block on flat silicon substrate. The polymer brushes are prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). We use a combinatorial design featuring a molecular weight gradient in the bottom neutral block to investigate systematically the effect of the molecular weight of that block on the stability of the copolymer brush. We measure variations in dry thickness of the diblock copolymer brush by ellipsometry after different incubation times in aqueous buffer (pH = 9.0) as a function of thickness of the neutral block, indicating degrafting of the mechanically activated copolymer chains via hydrolysis of ester groups in the initiator and/or Si–O bonds that attach the polymer to the substrate. The stability of the diblock copolymer brushes is higher than that of PAA homopolymer b...}, number={21}, journal={MACROMOLECULES}, author={Li, Yuanchao and Ko, Yeongun and Lin, Yiliang and Kiserow, Douglas and Genzer, Jan}, year={2017}, month={Nov}, pages={8580–8587} }
 @article{applin_schmitz_tiemsin_genzer_connell_wohl_2017, title={Further insight into the mechanism of poly(styrene-co-methyl methacrylate) microsphere formation}, volume={55}, ISSN={["1099-0518"]}, DOI={10.1002/pola.28612}, abstractNote={Polymeric microspheres have been utilized in a broad range of applications ranging from chromatographic separation techniques to analysis of air flow over aerodynamic surfaces. The preparation of microspheres from many different polymer families has consequently been extensively studied using a variety of synthetic approaches. Although there are a variety of methods of synthesis for polymeric microspheres, free-radical initiated emulsion polymerization is one of the most common techniques. In this work, poly(styrene-co-methyl methacrylate) microspheres were synthesized via surfactant-free emulsion polymerization. The effect of co-monomer composition and addition time on particle size distribution, particle formation, and particle morphology were investigated. Particles were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM) to gain further insight into particle size and size distributions. Reaction kinetics were analyzed alongside of characterization results. A particle formation mechanism for poly(styrene-co-methyl methacrylate) microspheres was proposed based on characterization results and known reaction kinetics.}, number={13}, journal={JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY}, author={Applin, Samantha I. and Schmitz, Russell C. and Tiemsin, Pacita I. and Genzer, Jan and Connell, John W. and Wohl, Christopher J.}, year={2017}, month={Jul}, pages={2249–2259} }
 @article{macewan_weitzhandler_hoffmann_genzer_gradzielski_chilkoti_2017, title={Phase Behavior and Self-Assembly of Perfectly Sequence-Defined and Monodisperse Multiblock Copolypeptides}, volume={18}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.6b01759}, abstractNote={This paper investigates how the properties of multiblock copolypeptides can be tuned by their block architecture, defined by the size and distribution of blocks along the polymer chain. These parameters were explored by the precise, genetically encoded synthesis of recombinant elastin-like polypeptides (ELPs). A family of ELPs was synthesized in which the composition and length were conserved while the block length and distribution were varied, thus creating 11 ELPs with unique block architectures. To our knowledge, these polymers are unprecedented in their intricately and precisely varied architectures. ELPs exhibit lower critical solution temperature (LCST) behavior and micellar self-assembly, both of which impart easily measured physicochemical properties to the copolymers, providing insight into polymer hydrophobicity and self-assembly into higher order structures, as a function of solution temperature. Even subtle variation in block architecture changed the LCST phase behavior and morphology of these ELPs, measured by their temperature-triggered phase transition and nanoscale self-assembly. Size and morphology of polypeptide micelles could be tuned solely by controlling the block architecture, thus demonstrating that when sequence can be precisely controlled, nanoscale self-assembly of polypeptides can be modulated by block architecture.}, number={2}, journal={BIOMACROMOLECULES}, author={MacEwan, Sarah R. and Weitzhandler, Isaac and Hoffmann, Ingo and Genzer, Jan and Gradzielski, Michael and Chilkoti, Ashutosh}, year={2017}, month={Feb}, pages={599–609} }
 @article{christau_moeller_genzer_koehler_klitzing_2017, title={Salt-Induced Aggregation of Negatively Charged Gold Nanoparticles Confined in a Polymer Brush Matrix}, volume={50}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.7b00866}, abstractNote={We report on the salt-induced aggregation of citrate-coated gold nanoparticles (AuNPs) confined within poly(N-isopropylacrylamide) (PNIPAM) brushes grafted from flat substrates. Compared to highly dispersed AuNPs, a red-shift and broadening of the surface plasmon (SP) band is observed when the AuNPs are confined by the PNIPAM brush matrix due to their close vicinity. Additional red-shifting and broadening occur upon immersion in aqueous salt solutions (1 M NaF, NaCl, NaBr, and KCl). Nanoparticle assemblies are established due to salt-induced aggregation of AuNPs and are dependent on the type of salt. In the presence of KCl, nanoparticle assemblies are built up that result in the formation a second plasmon peak at ∼700 nm. The color change of PNIPAM/AuNP is associated with (1) the collapse of the PNIPAM brushes in the presence of salt and (2) nanoparticle aggregation due to electrostatic screening of the negative charges around the AuNPs by the salt ions. Ion specificity is related to ion-pair association ...}, number={18}, journal={MACROMOLECULES}, author={Christau, Stephanie and Moeller, Tim and Genzer, Jan and Koehler, Ralf and Klitzing, Regine}, year={2017}, month={Sep}, pages={7333–7343} }
 @article{cooper_arutselvan_liu_armstrong_lin_khan_genzer_dickey_2017, title={Sensors: Stretchable Capacitive Sensors of Torsion, Strain, and Touch Using Double Helix Liquid Metal Fibers (Adv. Funct. Mater. 20/2017)}, volume={27}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/ADFM.201770124}, DOI={10.1002/ADFM.201770124}, abstractNote={Scanning electron micrographs of hollow elastic fibers. Injecting the core with liquid metal renders the fibers conductive. As Michael D. Dickey and co-workers present in article number 1605630, two or more fibers twisted together can sense large amounts of torsion due to changes in geometry, and therefore capacitance, between the fibers. Self-capacitance between fingers and the metal in the fibers allows for touch sensing.}, number={20}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Cooper, Christopher B. and Arutselvan, Kuralamudhan and Liu, Ying and Armstrong, Daniel and Lin, Yiliang and Khan, Mohammad Rashed and Genzer, Jan and Dickey, Michael D.}, year={2017}, month={May} }
 @article{liu_shaw_dickey_genzer_2017, title={Sequential self-folding of polymer sheets}, volume={3}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.1602417}, abstractNote={We demonstrate an innovative strategy for sequentially self-folding 2D polymer sheets into 3D objects using light.}, number={3}, journal={SCIENCE ADVANCES}, publisher={American Association for the Advancement of Science (AAAS)}, author={Liu, Ying and Shaw, Brandi and Dickey, Michael D. and Genzer, Jan}, year={2017}, month={Mar} }
 @article{lin_liu_genzer_dickey_2017, title={Shape-transformable liquid metal nanoparticles in aqueous solution}, volume={8}, ISSN={["2041-6539"]}, url={https://doi.org/10.1039/C7SC00057J}, DOI={10.1039/c7sc00057j}, abstractNote={This paper reports the formation of shape-changing and phase-transforming liquid metal particles that have potential applications in drug delivery, catalysis, colloidal jamming, and optics.}, number={5}, journal={CHEMICAL SCIENCE}, publisher={Royal Society of Chemistry (RSC)}, author={Lin, Yiliang and Liu, Yang and Genzer, Jan and Dickey, Michael D.}, year={2017}, month={May}, pages={3832–3837} }
 @article{cooper_arutselvan_liu_armstrong_lin_khan_genzer_dickey_2017, title={Stretchable Capacitive Sensors of Torsion, Strain, and Touch Using Double Helix Liquid Metal Fibers}, volume={27}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201605630}, abstractNote={Soft and stretchable sensors have the potential to be incorporated into soft robotics and conformal electronics. Liquid metals represent a promising class of materials for creating these sensors because they can undergo large deformations while retaining electrical continuity. Incorporating liquid metal into hollow elastomeric capillaries results in fibers that can integrate with textiles, comply with complex surfaces, and be mass produced at high speeds. Liquid metal is injected into the core of hollow and extremely stretchable elastomeric fibers and the resulting fibers are intertwined into a helix to fabricate capacitive sensors of torsion, strain, and touch. Twisting or elongating the fibers changes the geometry and, thus, the capacitance between the fibers in a predictable way. These sensors offer a simple mechanism to measure torsion up to 800 rad m−1—two orders of magnitude higher than current torsion sensors. These intertwined fibers can also sense strain capacitively. In a complementary embodiment, the fibers are injected with different lengths of liquid metal to create sensors capable of distinguishing touch along the length of a small bundle of fibers via self‐capacitance. The three capacitive‐based modes of sensing described here may enable new sensing applications that employ the unique attributes of stretchable fibers.}, number={20}, journal={ADVANCED FUNCTIONAL MATERIALS}, publisher={Wiley}, author={Cooper, Christopher B. and Arutselvan, Kuralamudhan and Liu, Ying and Armstrong, Daniel and Lin, Yiliang and Khan, Mohammad Rashed and Genzer, Jan and Dickey, Michael D.}, year={2017}, month={May} }
 @article{lin_gordon_khan_vasquez_genzer_dickey_2017, title={Vacuum filling of complex microchannels with liquid metal}, volume={17}, ISSN={["1473-0189"]}, url={https://doi.org/10.1039/C7LC00426E}, DOI={10.1039/c7lc00426e}, abstractNote={This paper describes the utilization of vacuum to fill complex microchannels with liquid metal.}, number={18}, journal={LAB ON A CHIP}, publisher={Royal Society of Chemistry (RSC)}, author={Lin, Yiliang and Gordon, Olivia and Khan, M. Rashed and Vasquez, Neyanel and Genzer, Jan and Dickey, Michael D.}, year={2017}, month={Sep}, pages={3043–3050} }
 @article{castillo_wilson_efimenko_dickey_gorman_genzer_2016, title={Amidation of Polyesters Is Slow in Nonaqueous Solvents: Efficient Amidation of Poly(ethylene terephthalate) with 3-Aminopropyltriethoxysilane in Water for Generating Multifunctional Surfaces}, volume={8}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/ACSAMI.6B12155}, DOI={10.1021/acsami.6b12155}, abstractNote={This paper describes surface functionalization of poly(ethylene terephthalate) (PET) films by transamidation of the ester groups with primary amines. The use of water as a solvent improves tremendously the reaction rate and yield compared to conventionally used alcohols. In this study, PET films were exposed to an aqueous solution of 3-aminopropyltriethoxysilane (APTES), which resulted in ester-to-amide reactions on the surface of the film. Hydrolysis of the resulting ethoxy moieties in APTES creates hydroxyl groups that can be used as anchoring points for further modification of PET films. This scheme offers an alternative approach to modify polyesters using water as the solvent.}, number={51}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Castillo, Gilbert A. and Wilson, Lance and Efimenko, Kirill and Dickey, Michael D. and Gorman, Christopher B. and Genzer, Jan}, year={2016}, month={Dec}, pages={35641–35649} }
 @article{lin_ladd_wang_martin_genzer_khan_dickey_2016, title={Drawing liquid metal wires at room temperature}, volume={7}, ISSN={2352-4316}, url={http://dx.doi.org/10.1016/J.EML.2016.03.010}, DOI={10.1016/J.EML.2016.03.010}, abstractNote={This paper describes an extremely facile method to fabricate metallic wires at room temperature. The wires form by stretching viscoelastic polymer substrates supporting a drop of gallium-based liquid metal. Stretching the polymer causes the metal to also elongate due to the adhesion between the two materials. The diameters of the resulting wires, which can be as small as 10 μm, decrease with increasing strain. This method is inspired by the process used for drawing optical fibers, which involves pulling a pre-form cylinder of molten glass until it thins to the size of a fiber. In contrast, the process here is done at room temperature and realized without the need for large forces. Moreover, geometries beyond simple wires are possible including parallel, core–shell, branched, and helix structures. The resulting wires can be elastic (stretchable), viscoelastic (soft), or plastic (stiff) depending on the chemistry and post-processing of the polymer. Wires can make electrical contacts by allowing the metal to sink through the viscoelastic polymer onto a substrate containing electrodes. In addition, removing the polymer substrate after elongation produces freestanding liquid metal wires stabilized by the surface oxide on the metal. Rheological studies show that polymers with a variety of properties can be utilized to form these wires including viscoelastic materials and gels. The ability to form metallic wires in a simple manner may find uses in soft and stretchable electronics, or enable new applications, such as ‘wires on demand’ for repairing electrical connections.}, journal={Extreme Mechanics Letters}, publisher={Elsevier BV}, author={Lin, Yiliang and Ladd, Collin and Wang, Siyao and Martin, Andre and Genzer, Jan and Khan, Saad A. and Dickey, Michael D.}, year={2016}, month={Jun}, pages={55–63} }
 @article{christau_moeller_brose_genzer_soltwedel_klitzing_2016, title={Effect of gold nanoparticle hydrophobicity on thermally induced color change of PNIPAM brush/gold nanoparticle hybrids}, volume={98}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2016.03.088}, abstractNote={This paper addresses the relation between gold nanoparticle (AuNP) distribution in thermoresponsive polymer brushes and the thermally induced color change of the polymer brush/AuNP hybrids. Therefore, we report on the effect of AuNP surface functionalization on the structure and optical response of the nanoparticles in thermoresponsive poly(N- isopropylacrylamide) (PNIPAM) brushes. Two different types of gold nanoparticles are attached to the PNIPAM brushes: (1) AuNPs that are coated with citrate anions (AuNP-citrate), and (2) AuNPs stabilized with 12-mercaptododecanoic acid ligands (AuNP-MDA). Neutron reflectivity (NR) measurements indicate that the spatial structure of the hybrid depends on the particle type. A strong increase in thickness is observed after attachment of AuNP-citrate; this is not the case for AuNP-MDA. The thermoinduced color change of the PNIPAM/AuNP hybrids depends strongly on the particle type. While a red-shift of the surface plasmon band occurs in case of AuNP-citrate, a blue-shift is found for AuNP-MDA when the temperature is increased above the PNIPAM's volume phase transition temperature. This blue-shift vanishes after a certain number of heating/cooling cycles, indicating a rearrangement of the AuNPs in the brush. The different behavior of AuNP-citrate as compared to AuNP-MDA can be explained by the hydrophobic nature of the 12-mercaptododecanoic acid ligands.}, journal={POLYMER}, author={Christau, Stephanie and Moeller, Tim and Brose, Felix and Genzer, Jan and Soltwedel, Olaf and Klitzing, Regine}, year={2016}, month={Aug}, pages={454–463} }
 @article{kopyshev_galvin_patil_genzer_lomadze_feldmann_zakrevski_santer_2016, title={Light-Induced Reversible Change of Roughness and Thickness of Photosensitive Polymer Brushes}, volume={8}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.6b06881}, abstractNote={We investigate light-induced changes in thickness and roughness of photosensitive polymer brushes containing azobenzene cationic surfactants by atomic force microscopy (AFM) in real time during light irradiation. Because the cis-state of azobenzene unit requires more free volume than its trans counterpart, the UV light-induced expansion of polymer thin films associated with the trans-to-cis isomerism of azobenzene groups is expected to occur. This phenomenon is well documented in physisorbed polymer films containing azobenzene groups. In contrast, photosensitive polymer brushes show a decrease in thickness under UV irradiation. We have found that the azobenzene surfactants in their trans-state form aggregates within the brush. Under irradiation, the surfactants undergo photoisomerization to the cis-state, which is more hydrophilic. As a consequence, the aggregates within the brush are disrupted, and the polymer brush contracts. When subsequently irradiated with blue light the polymer brush thickness returns back to its initial value. This behavior is related to isomerization of the surfactant to the more hydrophobic trans-state and subsequent formation of surfactant aggregates within the polymer brush. The photomechanical function of the dry polymer brush, i.e., contraction and expansion, was found to be reversible with repeated irradiation cycles and requires only a few seconds for switching. In addition to the thickness change, the roughness of the brush also changes reversibly between a few Angstroms (blue light) and several nanometers (UV light). Photosensitive polymer brushes represent smart films with light responsive thickness and roughness that could be used for generating dynamic fluctuating surfaces, the function of which can be turned on and off in a controllable manner on a nanometer length scale.}, number={29}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Kopyshev, Alexey and Galvin, Casey J. and Patil, Rohan R. and Genzer, Jan and Lomadze, Nino and Feldmann, David and Zakrevski, Juri and Santer, Svetlana}, year={2016}, month={Jul}, pages={19175–19184} }
 @article{oezcam_efimenko_spontak_fischer_genzer_2016, title={Multipurpose Polymeric Coating for Functionalizing Inert Polymer Surfaces}, volume={8}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.5b12216}, abstractNote={In this work, we report on the development of a highly functionalizable polymer coating prepared by the chemical coupling of trichlorosilane (TCS) to the vinyl groups of poly(vinylmethyl siloxane) (PVMS). The resultant PVMS-TCS copolymer can be coated as a functional organic primer layer on a variety of polymeric substrates, ranging from hydrophilic to hydrophobic. Several case studies demonstrating the remarkable and versatile properties of PVMS-TCS coatings are presented. In particular, PVMS-TCS is found to serve as a convenient precursor for the deposition of organosilanes and the subsequent growth of polymer brushes, even on hydrophobic surfaces, such as poly(ethylene terephthalate) and polypropylene. In this study, the physical and chemical characteristics of these versatile PVMS-TCS coatings are interrogated by an arsenal of experimental probes, including scanning electron microscopy, water contact-angle measurements, ellipsometry, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy.}, number={8}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Oezcam, A. Evren and Efimenko, Kirill and Spontak, Richard J. and Fischer, Daniel A. and Genzer, Jan}, year={2016}, month={Mar}, pages={5694–5705} }
 @article{kopyshev_galvin_genzer_lomadze_santer_2016, title={Polymer brushes modified by photosensitive azobenzene containing polyamines}, volume={98}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2016.03.050}, abstractNote={This paper describes a strategy for preparing photosensitive polymeric grafts on flat solid surfaces by loading diblock-copolymer or homopolymer brushes with cationic azobenzene-containing surfactants. In contrast to previous work, we utilize photosensitive surfactants that bear positively-charged polyamine head groups whose charge varies between 1+ and 3+. Poly(methylmethacrylate-b-methacrylic acid) (PMMA-b-PMAA) brushes were prepared by employing atom transfer radical polymerization, where the bottom poly(methyl methacrylate) block was grown first followed by the synthesis of t-butyl methacrylate block that after de-protection yielded poly(methacrylic acid). We used PMMA-b-PMAA brushes with constant grafting density and length of the PMMA block, and three different lengths of the PMAA block. The azobenzene-based surfactants attached only to the PMAA block. The degree of binding (i.e., the number of surfactant molecules per binding site on the brush backbone) of the surfactants to the brush depends strongly on the valence of the surfactant head-group; within the brushes the concentration of the surfactant carrying unit charge is larger than that of multivalent surfactants. We detect pronounced response of the brush topography on irradiation with UV interference pattern even at very low degree of binding (as small as 0.08) of multi-valence surfactant. Areas on the sample that receive the highest UV dose exhibit chain scission. By removing the ruptured chains from the substrate via good solvent, one uncovers a surface topographical relief grating, whose spatial arrangement follows the intensity distribution of the UV light on the sample during irradiation. Due to strong coupling of the multi-valence surfactants to the polymer brush, it was possible in some cases to completely remove the polyelectrolyte block from the PMMA layer. The application of multi-valence azobenzene surfactants for triggering brush photosensitive has important advantage over usage of surfactant with unit charge because relative to single-valence surfactants much lower concentrations of the multivalent surfactant are needed to achieve comparable response upon UV irradiation.}, journal={POLYMER}, author={Kopyshev, Alexey and Galvin, Casey J. and Genzer, Jan and Lomadze, Nino and Santer, Svetlana}, year={2016}, month={Aug}, pages={421–428} }
 @article{pandiyarajan_rubinstein_genzer_2016, title={Surface-Anchored Poly(N-isopropylacrylamide) Orthogonal Gradient Networks}, volume={49}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.6b01048}, abstractNote={We present a versatile synthetic route leading toward generating surface-attached polyacrylamide gels, in which the cross-link density varies continuously and gradually across the substrate in two orthogonal directions. We employ free radical polymerization to synthesize random copolymers comprising ~5% of photoactive methacrylyloxybenzophenone (MABP), ~5% of thermally active styrene sulfonyl azide (SSAz), and ~90% of N-isopropylacrylamide (NIPAAm) units. The presence of MABP and SSAz in the copolymer facilitates control over the cross-link density of the gel in an orthogonal manner using photoactivated and thermally activated cross-linking chemistries, respectively. Spectroscopic ellipsometry is employed to determine the degree of swelling of the gel in water and methanol as a function of position on the substrate. Network swelling varies continuously and gradually across the substrate and is high in regions of low gel fractions and low in regions of high gel fractions.}, number={14}, journal={MACROMOLECULES}, author={Pandiyarajan, C. K. and Rubinstein, Michael and Genzer, Jan}, year={2016}, month={Jul}, pages={5076–5083} }
 @article{galvin_genzer_2016, title={Swelling of Hydrophilic Polymer Brushes by Water and Alcohol Vapors}, volume={49}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.6b00111}, abstractNote={We examine the effect of end-tethering, grafting density (σ), chemistry of polymer side chain, and solvent type on the vapor swelling of hydrophilic polymer brushes. Using a library of samples derived by postpolymerization modification of a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brush, we determine the extent of vapor swelling and solvent uptake at different vapor pressures of water, methanol, and ethanol using spectroscopic ellipsometry. We compare the results from neat PDMAEMA and PDMAEMA quaternized by methyl iodide with chemically analogous samples prepared by spincasting bulk PDMAEMA. We find that brush samples swell to greater extents than spuncast samples, indicating a role for end-tethering in the vapor uptake process. Furthermore, vapor swelling of polymer brushes depends strongly on both polymer and solvent chemistry. We demonstrate that the extent to which σ affects vapor sorption inside the brush depends on polymer side chain chemistry, indicating an interdependence of the observe...}, number={11}, journal={MACROMOLECULES}, author={Galvin, Casey J. and Genzer, Jan}, year={2016}, month={Jun}, pages={4316–4329} }
 @article{cruz-teran_carlin_efimenko_genzer_rao_2016, title={Targeted Mutagenesis and Combinatorial Library Screening Enables Control of Protein Orientation on Surfaces and Increased Activity of Adsorbed Proteins}, volume={32}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.6b01446}, abstractNote={While nonspecific adsorption is widely used for immobilizing proteins on solid surfaces, the random nature of protein adsorption may reduce the activity of immobilized proteins due to occlusion of the active site. We hypothesized that the orientation a protein assumes on a given surface can be controlled by systematically introducing mutations into a region distant from its active site, thereby retaining activity of the immobilized protein. To test this hypothesis, we generated a combinatorial protein library by randomizing six targeted residues in a binding protein derived from highly stable, nonimmunoglobulin Sso7d scaffold; mutations were targeted in a region that is distant from the binding site. This library was screened to isolate binders that retain binding to its cognate target (chicken immunoglobulin Y, cIgY) as well as exhibit adsorption on unmodified silica at pH 7.4 and high ionic strength conditions. A single mutant, Sso7d-2B5, was selected for further characterization. Sso7d-2B5 retained binding to cIgY with an apparent dissociation constant similar to that of the parent protein; both mutant and parent proteins saturated the surface of silica with similar densities. Strikingly, however, silica beads coated with Sso7d-2B5 could achieve up to 7-fold higher capture of cIgY than beads coated with the parent protein. These results strongly suggest that mutations introduced in Sso7d-2B5 alter its orientation relative to the parent protein, when adsorbed on silica surfaces. Our approach also provides a generalizable strategy for introducing mutations in proteins so as to improve their activity upon immobilization, and has direct relevance to development of protein-based biosensors and biocatalysts.}, number={34}, journal={LANGMUIR}, author={Cruz-Teran, Carlos A. and Carlin, Kevin B. and Efimenko, Kirill and Genzer, Jan and Rao, Balaji M.}, year={2016}, month={Aug}, pages={8660–8667} }
 @misc{liu_genzer_dickey_2016, title={"2D or not 2D": Shape-programming polymer sheets}, volume={52}, ISSN={["1873-1619"]}, DOI={10.1016/j.progpolymsci.2015.09.001}, abstractNote={This review summarizes progress toward programming two-dimensional (2D) polymer sheets which respond to a variety of external stimuli to form three-dimensional (3D) shapes or topographical features on macroscopically planar sheets. Shape programming strategically adds value or function to 2D sheets, films, or coatings that can be created inexpensively. 2D substrates are common form factors that are compatible with ordinary 2D patterning techniques (i.e., inkjet, photolithography, roll-to-roll printing) and may be stored, packed, and shipped efficiently. Polymer materials are attractive due to their flexibility, light weight, low price, and compatibility with high throughput processing. This review highlights strategies for triggering shape change in planar polymeric materials. The strategies are divided into four broad categories: (1) 2D substrates with latent topography “programmed” using conventional microfabrication, (2) 2D substrates that form topography due to imposed or self-generated stress, (3) 2D substrates that form 3D shapes by out-of-plane bending, and (4) 2D substrates that use “hinges” to achieve out-of-plane folding. The review highlights all strategies while focusing primarily on last two approaches.}, journal={PROGRESS IN POLYMER SCIENCE}, publisher={Elsevier BV}, author={Liu, Ying and Genzer, Jan and Dickey, Michael D.}, year={2016}, month={Jan}, pages={79–106} }
 @article{datta_genzer_2016, title={"Grafting Through" Polymerization Involving Surface-Bound Monomers}, volume={54}, ISSN={["1099-0518"]}, DOI={10.1002/pola.27907}, abstractNote={ABSTRACT“Grafting through” polymerization represents copolymerization of free monomers in solution and polymerizable units bound to a substrate. Free polymer chains are formed initially in solution and can incorporate the surface‐bound monomers, and thereby, get covalently bonded to the surface during the polymerization process. As more growing chains attach to the surface‐bound monomers, an immobilized polymer layer is formed on the surface. We use a combination of computer simulation and experiments to comprehend this process for monomers bound to a flat impenetrable substrate. We concentrate specifically on addressing the effect of spatial density of the surface‐bound monomers on the formation of the surface‐attached polymers. We employ a lattice‐based Monte Carlo model utilizing the bond fluctuation model scheme to provide molecular‐level insight into the grafting process. For experimental validation, we create gradients of density of bound methacrylate units on flat silicon wafers using organosilane chemistry and carry out “grafting through” free radical polymerization initiated in bulk. We report that the proximity of the surface‐bound polymerizable units promotes the “grafting through” process but prevents more free growing chains to “graft through'' the polymerizable units. The “grafting through” process is self‐limiting in nature and does not affect the overall density of the surface‐bound polymer layer, except in case of the highest theoretical packing density of surface‐bound monomers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 263–274}, number={2}, journal={JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY}, author={Datta, Preeta and Genzer, Jan}, year={2016}, month={Jan}, pages={263–274} }
 @article{shen_rojas_genzer_gurgel_carbonell_2016, title={Affinity interactions of human immunoglobulin G with short peptides: role of ligand spacer on binding, kinetics, and mass transfer}, volume={408}, ISSN={["1618-2650"]}, DOI={10.1007/s00216-015-9135-y}, abstractNote={The interaction affinity between human IgG and a short peptide ligand (hexameric HWRGWV) was investigated by following the shifts in frequency and energy dissipation in a quartz crystal microbalance (QCM). HWRGWV was immobilized by means of poly(ethylene glycol) tethered on QCM sensors coated with silicon oxide, which enhanced the accessibility of the peptide to hIgG and also passivated the surface. Ellipsometry and ToF-SIMS were employed for surface characterization. The peptide ligand density was optimized to 0.88 chains nm(-2), which enabled the interaction of each hIgG molecule with at least one ligand. The maximum binding capacity was found to be 4.6 mg m(-2), corresponding to a monolayer of hIgG, similar to the values for chromatographic resins. Dissociation constants were lower than those obtained from resins, possibly due to overestimation of bound mass by QCM. Equilibrium thermodynamic and kinetic parameters were determined, shedding light on interfacial effects important for detection and bioseparation. Graphical Abstract The interaction affinity between human IgG and a short peptide ligand was investigated by using quartz crystal microgravimetry, ellipsometry and ToF-SIMS. Equilibrium thermodynamic and kinetics parameters were determined, shedding light on interfacial effects important for detection and bioseparation.}, number={7}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Shen, Fei and Rojas, Orlando J. and Genzer, Jan and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2016}, month={Mar}, pages={1829–1841} }
 @article{patil_kiserow_genzer_2015, title={Creating surface patterns of polymer brushes by degrafting via tetrabutyl ammonium fluoride}, volume={5}, ISSN={["2046-2069"]}, DOI={10.1039/c5ra17000a}, abstractNote={We demonstrate the use of tetrabutyl ammonium fluoride (TBAF) for creating spatial patterns of poly(methyl methacrylate) (PMMA) brushes on a flat silica support by degrafting PMMA grafted chains from selected regions on the substrate.}, number={105}, journal={RSC ADVANCES}, author={Patil, Rohan and Kiserow, Douglas and Genzer, Jan}, year={2015}, pages={86120–86125} }
 @article{patil_turgman-cohen_srogl_kiserow_genzer_2015, title={Direct Measurement of Molecular Weight and Grafting Density by Controlled and Quantitative Degrafting of Surface-Anchored Poly(methyl methacrylate)}, volume={4}, ISSN={["2161-1653"]}, DOI={10.1021/mz5007188}, abstractNote={We report on quantitative determination of the molecular weight distribution (MWD) and grafting density (σP) of polymer assemblies grown by controlled radical polymerization from flat substrates as a function of polymerization time and the ratio between the inhibitor and catalyst species. Specifically, we grow poly(methyl methacrylate) (PMMA) brushes on flat silica-based surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP), cleave the PMMA grafts quantitatively using tetrabutyl ammonium fluoride (TBAF), and analyze their MWD by size exclusion chromatography equipped with a high-sensitivity differential refractive index detector. The polymer growth and degrafting processes are followed by ellipsometry, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The σP is independent of polymerization time and increases with increasing SI-ATRP inhibitor/catalyst ratio. Specifically, σP increases from 0.48 ± 0.06 to 0.58 ± 0.06 chains/nm2 as the inhibitor/catalyst molar ratio increases from 0 to 0.015, respectively, providing evidence that high inhibitor/catalyst ratio offers better control of the SI-ATRP reaction, by lowering number of terminations, and leading to denser PMMA brush assemblies.}, number={2}, journal={ACS MACRO LETTERS}, author={Patil, Rohan R. and Turgman-Cohen, Salomon and Srogl, Jiri and Kiserow, Douglas and Genzer, Jan}, year={2015}, month={Feb}, pages={251–254} }
 @article{klok_genzer_2015, title={Expanding the Polymer Mechanochemistry Toolbox through Surface-Initiated Polymerization}, volume={4}, ISSN={["2161-1653"]}, DOI={10.1021/acsmacrolett.5b00295}, abstractNote={Surface-initiated polymerizations represent a versatile toolbox to generate densely grafted assemblies of chain end-tethered polymers. At sufficiently short interchain distances, surface-grafted polymers are forced into an extended chain conformation, which forms the basis of several unique properties, including their ability to withstand efficiently biofouling or to act as low friction coatings. While the effect on materials properties is well-established, only relatively recently first reports have appeared describing that chain stretching in surface-grafted polymer films also impacts chemical stability/reactivity. This Viewpoint presents surface-initiated polymerization as an alternative polymer mechanochemical tool. The absence of an external force field to induce chain elongation and the possibility to modulate chain stretching by varying brush molecular weight and grafting density, in conjunction with electrostatic interactions and nanoinclusions that may be present inside the polymeric grafts, make surface-initiated polymerization an attractive tool to both study and understand the effects of polymer chain conformation on the stability/reactivity of surface-grafted polymers.}, number={6}, journal={ACS MACRO LETTERS}, author={Klok, Harm-Anton and Genzer, Jan}, year={2015}, month={Jun}, pages={636–639} }
 @article{cai_yuan_blencowe_qiao_genzer_spontak_2015, title={Film-Stabilizing Attributes of Polymeric Core-Shell Nanoparticles}, volume={9}, ISSN={["1936-086X"]}, DOI={10.1021/acsnano.5b00237}, abstractNote={Self-organization of nanoparticles into stable, molecularly thin films provides an insightful paradigm for manipulating the manner in which materials interact at nanoscale dimensions to generate unique material assemblies at macroscopic length scales. While prior studies in this vein have focused largely on examining the performance of inorganic or organic/inorganic hybrid nanoparticles (NPs), the present work examines the stabilizing attributes of fully organic core-shell microgel (CSMG) NPs composed of a cross-linked poly(ethylene glycol dimethacrylate) (PEGDMA) core and a shell of densely grafted, but relatively short-chain, polystyrene (PS) arms. Although PS homopolymer thin films measuring from a few to many nanometers in thickness, depending on the molecular weight, typically dewet rapidly from silica supports at elevated temperatures, spin-coated CSMG NP films measuring as thin as 10 nm remain stable under identical conditions for at least 72 h. Through the use of self-assembled monolayers (SAMs) to alter the surface of a flat silica-based support, we demonstrate that such stabilization is not attributable to hydrogen bonding between the acrylic core and silica. We also document that thin NP films consisting of three or less layers (10 nm) and deposited onto SAMs can be fully dissolved even after extensive thermal treatment, whereas slightly thicker films (40 nm) on Si wafer become only partially soluble during solvent rinsing with and without sonication. Taken together, these observations indicate that the present CSMG NP films are stabilized primarily by multidirectional penetration of relatively short, unentangled NP arms caused by NP layering, rather than by chain entanglement as in linear homopolymer thin films. This nanoscale "velcro"-like mechanism permits such NP films, unlike their homopolymer counterparts of comparable chain length and thickness, to remain intact as stable, free-floating sheets on water, and thus provides a viable alternative to ultrathin organic coating strategies.}, number={8}, journal={ACS NANO}, author={Cai, Xiao-Jing and Yuan, Hao-Miao and Blencowe, Anton and Qiao, Greg G. and Genzer, Jan and Spontak, Richard J.}, year={2015}, month={Aug}, pages={7940–7949} }
 @article{lin_cooper_wang_adams_genzer_dickey_2015, title={Handwritten, Soft Circuit Boards and Antennas Using Liquid Metal Nanoparticles}, volume={11}, ISSN={["1613-6829"]}, DOI={10.1002/smll.201502692}, abstractNote={Soft conductors are created by embedding liquid metal nanoparticles between two elastomeric sheets. Initially, the particles form an electrically insulating composite. Soft circuit boards can be handwritten by a stylus, which sinters the particles into conductive traces by applying localized mechanical pressure to the elastomeric sheets. Antennas with tunable frequencies are formed by sintering nanoparticles in microchannels.}, number={48}, journal={SMALL}, publisher={Wiley}, author={Lin, Yiliang and Cooper, Christopher and Wang, Meng and Adams, Jacob J. and Genzer, Jan and Dickey, Michael D.}, year={2015}, month={Dec}, pages={6397–6403} }
 @article{galvin_bain_henke_genzer_2015, title={Instability of Surface-Grafted Weak Polyacid Brushes on Flat Substrates}, volume={48}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ACS.MACROMOL.5B01289}, DOI={10.1021/ACS.MACROMOL.5B01289}, abstractNote={We study the stability of weak polyacid brush (WPAB) gradients in aqueous media covering a range in grafting density (σ) spanning 0.05–0.5 chains/nm2 using two analogous surface-anchored bromoisobutyrate-based initiators for atom transfer radical polymerization (ATRP) bearing either an ester or amide linker. Variations in dry thickness of ester-based WPABs as a function of time and pH are consistent with WPAB degrafting via linker hydrolysis catalyzed by mechanical tension in the grafted chains. Sources of tension considered include high σ, as well as swelling and electrostatic repulsion associated with increasing degree of deprotonation (α) of repeat units in the WPAB. Normalized thickness of the WPAB decreases by a maximum amount at intermediate σ between ∼0.05−0.15 chains/nm2, implying that contributions to tension by α are counterbalanced by charge regulation in the WPAB at high σ. Amide-based WPABs are more stable up to 264 h incubation, suggesting that commonly used ester-bearing ATRP initiators are...}, number={16}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Galvin, Casey J. and Bain, Erich D. and Henke, Adam and Genzer, Jan}, year={2015}, month={Aug}, pages={5677–5687} }
 @article{kopyshev_lomadze_feldmann_genzer_santer_2015, title={Making polymer brush photosensitive with azobenzene containing surfactants}, volume={79}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2015.09.023}, abstractNote={We report on rendering polyelectrolyte brushes photosensitive by loading them with azobenzene-containing cationic surfactants. Planar poly(methacrylic acid) (PMAA) brushes are synthesized using the "grafting from" free-radical polymerization scheme followed by exposure to a solution of photosensitive surfactants consisting of positively-charged head groups and hydrophobic tails into which azobenzene moieties are inserted. In this study the length of the hydrophobic methylene spacer connecting the azobenzene and the charged head group ranges from 4 to 10 CH2 groups. Under irradiation with UV light, the photo-isomerization of azobenzene integrated into a surfactant results in a change in size, geometry, dipole moment and free volume of the whole molecule. When the brush loaded with photosensitive surfactants is exposed to irradiation with UV interference patterns, the topography of the brush deforms following the distribution of the light intensity, exhibiting surface relief gratings (SRG). Since SRG formation is accompanied by a local rupturing of polymer chains in areas from which the polymer material is receding, most of the polymer material is removed from the surface during treatment with good solvent, leaving behind characteristic patterns of lines or dots. The azobenzene molecules still integrated within the polymer film can be removed by washing the brush with water. The remaining nano-structured brush can then be re-used for further functionalization. Although the opto-mechanically induced rupturing occurs for all surfactants, larger species do not penetrate deep enough into the brush such that after rupturing a leftover layer of polymer material remains on the substrate. This indicates that rupturing occurs predominantly in regions of high surfactant density.}, journal={POLYMER}, author={Kopyshev, Alexey and Lomadze, Nino and Feldmann, David and Genzer, Jan and Santer, Svetlana}, year={2015}, month={Nov}, pages={65–72} }
 @article{mailen_liu_dickey_zikry_genzer_2015, title={Modelling of shape memory polymer sheets that self-fold in response to localized heating}, volume={11}, ISSN={["1744-6848"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84943141129&partnerID=MN8TOARS}, DOI={10.1039/c5sm01681a}, abstractNote={We conduct a nonlinear finite element analysis (FEA) of the thermo-mechanical shrinking and self-folding behavior of pre-strained polystyrene polymer sheets.}, number={39}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Mailen, Russell W. and Liu, Ying and Dickey, Michael D. and Zikry, Mohammed and Genzer, Jan}, year={2015}, pages={7827–7834} }
 @article{shivapooja_yu_orihuela_mays_rittschof_genzer_lopez_2015, title={Modification of Silicone Elastomer Surfaces with Zwitterionic Polymers: Short-Term Fouling Resistance and Triggered Biofouling Release}, volume={7}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.5b09199}, abstractNote={We present a method for dual-mode-management of biofouling by modifying surface of silicone elastomers with zwitterionic polymeric grafts. Poly(sulfobetaine methacrylate) was grafted from poly(vinylmethylsiloxane) elastomer substrates using thiol-ene click chemistry and surface-initiated, controlled radical polymerization. These surfaces exhibited both fouling resistance and triggered fouling-release functionality. The zwitterionic polymers exhibited fouling resistance over short-term (∼hours) exposure to bacteria and barnacle cyprids. The biofilms that eventually accumulated over prolonged-exposure (∼days) were easily detached by applying mechanical strain to the elastomer substrate. Such dual-functional surfaces may be useful in developing environmentally and biologically friendly coatings for biofouling management on marine, industrial, and biomedical equipment because they can obviate the use of toxic compounds.}, number={46}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Shivapooja, Phanindhar and Yu, Qian and Orihuela, Beatriz and Mays, Robin and Rittschof, Daniel and Genzer, Jan and Lopez, Gabriel P.}, year={2015}, month={Nov}, pages={25586–25591} }
 @article{patil_turgman-cohen_srogl_kiserow_genzer_2015, title={On-Demand Degrafting and the Study of Molecular Weight and Grafting Density of Poly(methyl methacrylate) Brushes on Flat Silica Substrates}, volume={31}, ISSN={["0743-7463"]}, DOI={10.1021/la5044766}, abstractNote={We report on degrafting of surface-anchored poly(methyl methacrylate) (PMMA) brushes from flat silica-based substrates using tetrabutylammonium fluoride (TBAF) and determining their molecular weight distribution (MWD) using size exclusion chromatography (SEC). The grafted PMMA layer was synthesized using surface-initiated atom transfer radical polymerization (SI-ATRP) of MMA for polymerization times ranging from 6 to 24 h. X-ray photoelectron spectroscopy, ellipsometry, and time-of-flight secondary ion mass spectrometry were employed in tandem to characterize the degrafting process. The SEC eluograms were fit to various polymer distributions, namely Zimm-Schulz, ATRP in continuous stirred tank reactor, Wesslau, Schulz-Flory, and Smith et al. The ATRP model gives the best fit to the experimental data. The dry PMMA brush thickness and the number-average molecular weight (obtained from the MWD) suggest that the grafting density of the PMMA grafts is independent of polymerization time, indicating well-controlled/living growth of MMA. The observed polydispersity index (PDI) was higher than that generally observed in bulk grown polymers under similar conditions, indicating an effect due to chain confinement and crowding. We detect small but noticeable dependence of the polymer brush grafting density on the inhibitor/catalyst ratio. Higher inhibitor/catalyst ratio offers better control with lower early terminations, which results in a small increase in the apparent grafting density of the chains.}, number={8}, journal={LANGMUIR}, author={Patil, Rohan R. and Turgman-Cohen, Salomon and Srogl, Jiri and Kiserow, Douglas and Genzer, Jan}, year={2015}, month={Mar}, pages={2372–2381} }
 @article{malik_genzer_hall_2015, title={Proteinlike Copolymers as Encapsulating Agents for Small-Molecule Solutes}, volume={31}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.5b00032}, abstractNote={We describe the utilization of proteinlike copolymers (PLCs) as encapsulating agents for small-molecule solutes. We perform Monte Carlo simulations on systems containing PLCs and model solute molecules in order to understand how PLCs assemble in solution and what system conditions promote solute encapsulation. Specifically, we explore how the chemical composition of the PLCs and the range and strength of molecular interactions between hydrophobic segments on the PLC and solute molecules affect the solute encapsulation efficiency. The composition profiles of the hydrophobic and hydrophilic segments, the solute, and implicit solvent (or voids) within the PLC globule are evaluated to gain a complete understanding of the behavior in the PLC/solute system. We find that a single-chain PLC encapsulates solute successfully by collapsing the macromolecule to a well-defined globular conformation when the hydrophobic/solute interaction is at least as strong as the interaction strength among hydrophobic segments and the interaction among solute molecules is at most as strong as the hydrophobic/solute interaction strength. Our results can be used by experimentalists as a framework for optimizing unimolecular PLC solute encapsulation and can be extended potentially to applications such as "drug" delivery via PLCs.}, number={11}, journal={LANGMUIR}, author={Malik, Ravish and Genzer, Jan and Hall, Carol K.}, year={2015}, month={Mar}, pages={3518–3526} }
 @article{davis_chen_dickey_genzer_2016, title={Self-Folding of Thick Polymer Sheets Using Gradients of Heat}, volume={8}, ISSN={["1942-4310"]}, DOI={10.1115/1.4032209}, abstractNote={Self-folding converts two-dimensional (2D) sheets into three-dimensional (3D) objects in a hands-free manner. This paper demonstrates a simple approach to self-fold commercially available, millimeter-thick thermoplastic polymer sheets. The process begins by first stretching poly(methyl methacrylate) (PMMA), polystyrene (PS), or polycarbonate (PC) sheets using an extensometer at elevated temperatures close to the glass transition temperature (Tg) of each sheet. Localizing the strain to a small strip creates a “hinge,” which folds in response to asymmetric heating of the sheet. Although there are a number of ways to supply heat, here a heat gun delivers heat to one side of the hinge to create the necessary temperature gradient through the polymer sheet. When the local temperature exceeds the Tg of the polymer, the strain in the hinged region relaxes. Because strain relaxation occurs gradually across the sheet thickness, the polymer sheet folds in the direction toward the heating source. A simple geometric model predicts the dihedral angle of the sheet based on the thickness of the sheet and width of the hinge. This paper reports for the first time that this approach to folding works for a variety of thermoplastics using sheets that are significantly thicker (∼10 times) than those reported previously.}, number={3}, journal={JOURNAL OF MECHANISMS AND ROBOTICS-TRANSACTIONS OF THE ASME}, publisher={ASME International}, author={Davis, Duncan and Chen, Bin and Dickey, Michael D. and Genzer, Jan}, year={2016}, month={Jun} }
 @article{davis_mailen_genzer_dickey_2015, title={Self-folding of polymer sheets using microwaves and graphene ink}, volume={5}, ISSN={2046-2069}, url={http://dx.doi.org/10.1039/C5RA16431A}, DOI={10.1039/C5RA16431A}, abstractNote={Self-folding represents an attractive way to convert two-dimensional (2D) material sheets into three-dimensional (3D) objects in a hands-free manner. This paper describes a simple approach to self-fold pre-strained polystyrene (PS) sheets using microwaves.}, number={108}, journal={RSC Advances}, publisher={Royal Society of Chemistry (RSC)}, author={Davis, Duncan and Mailen, Russell and Genzer, Jan and Dickey, Michael D.}, year={2015}, pages={89254–89261} }
 @article{yenice_schoen_bildirir_genzer_klitzing_2015, title={Thermoresponsive PDMAEMA Brushes: Effect of Gold Nanoparticle Deposition}, volume={119}, ISSN={["1520-6106"]}, DOI={10.1021/acs.jpcb.5b04757}, abstractNote={The paper addresses the effect of gold nanoparticle (Au-NP) deposition on the thermoresponsive volume phase transition of the weak polyelectrolyte poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. PDMAEMA brushes were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP). The PDMAEMA/Au-NP composite brushes were fabricated by immersing the brush modified wafer in the Au-NP suspension. Atomic force microscopy (AFM), ellipsometry, and scanning electron microscopy (SEM) have been employed to characterize the neat PDMAEMA brushes and PDMAEMA/Au-NP composite brushes. All neat PDMAEMA brushes swelled below the volume phase transition temperature and collapsed with increasing temperature over a broad temperature range independent of the initial brush thickness. Water uptake of the brushes is also independent of initial brush thickness. The adsorption of the charged Au-NPs significantly affects the degree of swelling and the thermoresponsive properties of the brushes. PDMAEMA/Au-NP composite brushes do not exhibit any noticeable phase transition at the experimental temperature range irrespective of the initial brush thickness. The reason for this behavior is attributed to a combination of the following: the decreased conformational entropy of the Au-NP adsorbed polymer chains, the increased hydrophilicity of the system due to the charged Au-NPs, and the ≈13 nm diameter Au-NPs causing steric hindrance. We have also shown that the AFM full-indentation method can be successfully applied to determine the polymer brush thicknesses.}, number={32}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Yenice, Zuleyha and Schoen, Sebastian and Bildirir, Hakan and Genzer, Jan and Klitzing, Regine}, year={2015}, month={Aug}, pages={10348–10358} }
 @article{schoch_genzer_2014, title={Adsorption of "soft" spherical particles onto sinusoidally-corrugated substrates}, volume={10}, DOI={10.1039/c4sm01610f}, abstractNote={We utilize a Monte Carlo simulation scheme based on the bond fluctuation model to simulate settlement of “soft” adhesive particles onto sinusoidally-corrugated substrates.}, number={38}, journal={Soft Matter}, author={Schoch, P. K. and Genzer, Jan}, year={2014}, pages={7452–7458} }
 @article{schoch_genzer_2014, title={Adsorption of Multiple Spherical Particles onto Sinusoidally Corrugated Substrates}, volume={30}, ISSN={["0743-7463"]}, DOI={10.1021/la502026g}, abstractNote={We utilize a Monte Carlo simulation scheme based on the bond fluctuation model to simulate settlement of adhesive particles onto sinusoidally corrugated substrates. The particles are composed of a hard inner core with either an effective potential shell or a "soft" adhesive shell made of flexible arms attached to the particle surface. These chains adhere via either the effective potential shell or the sticky chain ends to the surface via pairwise nonspecific interactions. This simulation model allows for multiple particles to settle onto each tested substrate to elucidate the behavior of the collective adhesive layer featuring multiparticle assembly. Particles move within a 3D lattice space and settle on the substrate due to attractive particle/substrate interactions. Once a single particle adheres to the substrate, a new particle is introduced into the lattice to begin a new settlement. Through this multiparticle settlement mode, we explore the interplay among the characteristics of the particles (i.e., size, interaction shell) and the substrates (i.e., wavelength and periodicity) as well as interparticle interactions. We report that the adhesion of particles with an effective interaction shell to the substrates is reduced dramatically when the particle size is smaller than the feature width of the periodic substrate. The settlement of particles with flexible hair on the sinusoidally corrugated substrates is more complex. Specifically, the presence of flexible polymeric hairs makes the particle settlement more likely to occur on nearly all substrates studied irrespective of the characteristics of the substrate.}, number={31}, journal={LANGMUIR}, author={Schoch, Phillip K. and Genzer, Jan}, year={2014}, month={Aug}, pages={9407–9417} }
 @article{gurarslan_hardrict_roy_galvin_hill_gracz_sumerlin_genzer_tonelli_2015, title={Beyond Microstructures: Using the Kerr Effect to Characterize the Macrostructures of Synthetic Polymers}, volume={53}, ISSN={["1099-0488"]}, DOI={10.1002/polb.23598}, abstractNote={ABSTRACTThe macrostructures of synthetic polymers are essentially the complete molecular chain architectures, including the types and amounts of constituent short‐range microstructures, such as the regio‐ and stereosequences of the inserted monomers, the amounts and sequences of monomers found in co‐, ter‐, and tetra‐polymers, branching, inadvertent, and otherwise, etc. Currently, the best method for characterizing polymer microstructures uses high field, high resolution 13C‐nuclear magnetic resonance (NMR) spectroscopy observed in solution. However, even 13C‐NMR is incapable of determining the locations or positions of resident polymer microstructures, which are required to elucidate their complete macrostructures. The sequences of amino acid residues in proteins, or their primary structures, cannot be characterized by NMR or other short‐range spectroscopic methods, but only by decoding the DNA used in their syntheses or, if available, X‐ray analysis of their single crystals. Similarly, there are currently no experimental means to determine the sequences or locations of constituent microstructures along the chains of synthetic macromolecules. Thus, we are presently unable to determine their macrostructures. As protein tertiary and quaternary structures and their resulting ultimate functions are determined by their primary sequence of amino acids, so too are the behaviors and properties of synthetic polymers critically dependent on their macrostructures. We seek to raise the consciousness of both synthetic and physical polymer scientists and engineers to the importance of characterizing polymer macrostructures when attempting to develop structure–property relations. To help achieve this task, we suggest using the electrical birefringence or Kerr effects observed in their dilute solutions. The molar Kerr constants of polymer solutes contributing to the birefringence of their solutions, under the application of a strong electric field, are highly sensitive to both the types and locations of their constituent microstructures. As a consequence, we may begin to characterize the macrostructures of synthetic polymers by means of the Kerr effect. To simplify implementation of the Kerr effect to characterize polymer macrostructures, we suggest that NMR first be used to determine the types and amounts of constituent microstructures present. Subsequent comparison of observed Kerr effects with those predicted for different microstructural locations along the polymer chains can then be used to identify the most likely macrostructures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 155–166}, number={3}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Gurarslan, Rana and Hardrict, Shauntrece and Roy, Debashish and Galvin, Casey and Hill, Megan R. and Gracz, Hanna and Sumerlin, Brent S. and Genzer, Jan and Tonelli, Alan}, year={2015}, month={Feb}, pages={155–166} }
 @article{christau_moeller_yenice_genzer_klitzing_2014, title={Brush/Gold Nanoparticle Hybrids: Effect of Grafting Density on the Particle Uptake and Distribution within Weak Polyelectrolyte Brushes}, volume={30}, ISSN={["0743-7463"]}, DOI={10.1021/la503432x}, abstractNote={The effect of the brush grafting density on the loading of 13 nm gold nanoparticles (AuNPs) into stimuli-responsive poly(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) brushes anchored to flat impenetrable substrates is reported. Atom-transfer radical polymerization (ATRP) is used to grow polymer brushes via a "grafting from" approach from a 2-bromo-2-methyl-N-(3-(triethoxysilyl) propyl) propanamide (BTPAm)-covered silicon substrate. The grafting density is varied by using mixtures of initiator and a "dummy" molecule that is not able to initiate polymerization. A systematic study is carried out by varying the brush grafting density while keeping all of the other parameters constant. X-ray reflectivity is a suitable tool for investigating the spatial structure of the hybrid, and it is combined with scanning electron microscopy and UV/vis spectroscopy to study the particle loading and interpenetration of the particles within the polymer brush matrix. The particle uptake increases with decreasing grafting density and is highest for an intermediate grafting density because more space between the polymer chains is available. For very low grafting densities of PDMAEMA brushes, the particle uptake decreases because of a lack of the polymer matrix for the attachment of particles. The structure of the surface-grafted polymer chains changes after particle attachment. More water is incorporated into the brush matrix after particle immobilization, which leads to a swelling of the polymer chains in the hybrid material. Water can be removed from the brush by decreasing the relative humidity, which leads to brush shrinking and forces the AuNPs to get closer to each other.}, number={43}, journal={LANGMUIR}, author={Christau, Stephanie and Moeller, Tim and Yenice, Zuleyha and Genzer, Jan and Klitzing, Regine}, year={2014}, month={Nov}, pages={13033–13041} }
 @article{özçam_efimenko_genzer_2014, title={Effect of ultraviolet/ozone treatment on the surface and bulk properties of poly(dimethyl siloxane) and poly(vinylmethyl siloxane) networks}, volume={55}, ISSN={0032-3861}, url={http://dx.doi.org/10.1016/J.POLYMER.2014.05.027}, DOI={10.1016/J.POLYMER.2014.05.027}, abstractNote={We present a comparative study aiming at comprehending the effect of ultraviolet/ozone treatment on the modification of poly(dimethyl siloxane) (PDMS) and poly(vinylmethyl siloxane) (PVMS) silicone elastomers networks (SENs). Both PDMS and PVMS SENs undergo dramatic changes in their properties when exposed to UVO. The surface chemical composition of both PDMS and PVMS at long UVO treatment times changes substantially and features a high density of hydrophilic groups. There are two major differences in behavior in the two classes of materials. First, relative to PDMS, the PVMS-based SENs get modified throughout the entire bulk. Second, the physico-chemical changes detected in PVMS take place on much shorter time scale relative to PDMS. These results are in accord with our earlier reports that indicated that when exposed to UVO, the topmost ≈5 nm of PDMS gets converted into a silica-like material, which then acts as a barrier for diffusion of atomic oxygen. In this case, the bulk of PDMS maintains its elasticity. In contrast, both the surface and bulk of PVMS films undergo substantial changes in properties when exposed to UVO. First, the surface modification of PVMS SENs takes place after only a few seconds of the UVO treatment. In addition, we register substantial modification of bulk properties, including the complete densification accompanied with increased bulk modulus. Likely, the susceptibility of the vinyl bonds to radical reactions is responsible for this effect.}, number={14}, journal={Polymer}, publisher={Elsevier BV}, author={Özçam, A. Evren and Efimenko, Kirill and Genzer, Jan}, year={2014}, month={Jun}, pages={3107–3119} }
 @article{cai_genzer_spontak_2014, title={Evolution of Homopolymer Thin-Film Instability on Surface-Anchored Diblock Copolymers Varying in Composition}, volume={30}, ISSN={["0743-7463"]}, DOI={10.1021/la503046n}, abstractNote={The stability of molecularly thin polymer films deposited on various material substrates is of critical importance to many contemporary nanotechnologies involving functional coatings and nano/micropatterned surfaces, in which case the causes responsible for film destabilization must be fully understood. Previous experimental studies report that factors such as film thickness and polymer molecular weight play significant roles in governing the rate, as well as mechanism, of destabilization. Complementary theoretical predictions reveal that surface heterogeneities can likewise induce (and regulate the process of) destabilization. In this study, we investigate the destabilization rate and mechanism of homopolystyrene (PS) films differing in thickness on top of poly(styrene-b-methyl methacrylate) (SM) diblock copolymer monolayers varying in chemical composition anchored to flat silica-like substrates to examine the effect of surface constitution on PS stability. Copolymers with a long M block consistently promote PS dewetting by nucleation and growth, wherein the linear dewetting rate decreases monotonically with increasing PS molecular weight, film thickness, and S fraction in the SM copolymer. In analogous studies involving a copolymer with a relatively short M block, however, PS dewetting proceeds instead by spinodal dewetting that evolves gradually into nucleation and growth as the film thickness is increased.}, number={39}, journal={LANGMUIR}, author={Cai, Xiao-Jing and Genzer, Jan and Spontak, Richard J.}, year={2014}, month={Oct}, pages={11689–11695} }
 @article{allensworth_liu_braun_genzer_dickey_2014, title={In-plane deformation of shape memory polymer sheets programmed using only scissors}, volume={55}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2014.07.042}, abstractNote={Abstract This paper describes an unconventional, yet simple method to program sheets of shape memory polymer into a variety of two dimensional (2D) structures. The final shape is “encoded” by physically cutting an initial design out of a pre-strained film. The orientation of the initial cut-out relative to the direction of strain and the subsequent relaxation of strain via heating defines the final shape. The appeal of the approach described here is that an easy, low-cost cutting method can achieve a similar shape memory effect attained by more complex processing techniques. Unlike conventional methods, where the final shape of a shape memory polymer must be defined a priori, the direction of cutting of the polymer defines its final shape without any complex pre-programmed strain profiles. A geometric model relating the resolved 2D polymer shape to the initial shape and strain orientation reveals linear correlation between the model-predicted and experimentally-observed shapes. In addition to demonstrating the principle with simple rectangular shapes, we suggest geometries related to encryption and high aspect ratio fibers.}, number={23}, journal={POLYMER}, publisher={Elsevier BV}, author={Allensworth, James R. and Liu, Ying and Braun, Hayley and Genzer, Jan and Dickey, Michael D.}, year={2014}, month={Nov}, pages={5948–5952} }
 @article{christau_genzer_klitzing_2015, title={Polymer Brush/Metal Nanoparticle Hybrids for Optical Sensor Applications: from Self-Assembly to Tailored Functions and Nanoengineering}, volume={229}, ISSN={["0942-9352"]}, DOI={10.1515/zpch-2014-0573}, abstractNote={Abstract
               This review article summarizes the progress of research in the field
of polymer brush/metal nanoparticle hybrid materials. We will
discuss the mutual influence of polymer brush matrix and
particles. Self-assembly of particles within polymer brushes, and ways
to control the loading and location of nanoparticles inside polymer
brushes will be described, as well as the possibility to use the brush
templates as nanoreactors to generate metal nanoparticles. The
combination of stimuli-responsive polymer brushes and nanoparticles
exhibiting surface plasmon resonance, such as gold or silver, enables
the design of optical sensors based on reversible variations of the
brush conformation. Sensing devices are capable of detecting a variety
of extrinsic variations in their surrounding enviroments. The progress
in the development of such optical sensors using brush/particle
hybrids will be discussed in more detail.}, number={7-8}, journal={ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS}, author={Christau, Stephanie and Genzer, Jan and Klitzing, Regine}, year={2015}, month={Aug}, pages={1089–1117} }
 @article{hayes_liu_genzer_lazzi_dickey_2014, title={Self-Folding Origami Microstrip Antennas}, volume={62}, ISSN={["1558-2221"]}, DOI={10.1109/tap.2014.2346188}, abstractNote={This communication presents antennas that incorporate self-folding polymer substrates that transform planar, two-dimensional structures into three-dimensional antennas when exposed to a light source. Pre-strained polystyrene sheets supporting a patterned copper foil form the light-activated structures. Black ink that is inkjet printed on the polymer substrate selectively absorbs light and controls the shape of the transformation. This approach represents a simple method to reconfigure the shape of an antenna and a hands-free method to assemble 3D antennas from many of the conventional methods that are used to pattern 2D metal foils. We demonstrate and characterize two embodiments that highlight this concept: a monopole antenna that transforms from a conventional microstrip transmission line and a microstrip patch antenna that converts within seconds into a monopole antenna.}, number={10}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Hayes, Gerard J. and Liu, Ying and Genzer, Jan and Lazzi, Gianluca and Dickey, Michael D.}, year={2014}, month={Oct}, pages={5416–5419} }
 @article{liu_mailen_zhu_dickey_genzer_2014, title={Simple geometric model to describe self-folding of polymer sheets}, volume={89}, ISSN={["1550-2376"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000334306400006&KeyUID=WOS:000334306400006}, DOI={10.1103/physreve.89.042601}, abstractNote={Self-folding is the autonomous folding of two-dimensional shapes into three-dimensional forms in response to an external stimulus. This paper focuses on light-induced self-folding of prestrained polymer sheets patterned with black ink. The ink absorbs the light and the resulting heat induces the polymer beneath the ink to relax faster than the rest of the sheet. A simple geometric model captures both the folding angle and folding kinetics associated with this localized shrinkage. The model assumes that (1) the polymer in contact with the ink shrinks at a rate determined by the temporal temperature profile of the hinge surface; (2) the bottom of the sheet, which is cooler, does not shrink considerably; and (3) a linear gradient of strain relaxation exists across the film between these two extremes. Although there are more complex approaches for modeling folding, the appeal of this model is its simplicity and ease of use. Measurements of the macroscopic, thermally driven shrinkage behavior of the sheets help predict the kinetics of folding by determining how fast the top of the hinge shrinks as a function of temperature and time. These measurements also provide information about the temperature required to induce folding and offer indirect measurement of the glass transition temperature of the polymer that comprises the sheet.}, number={4}, journal={PHYSICAL REVIEW E}, publisher={American Physical Society (APS)}, author={Liu, Ying and Mailen, Russell and Zhu, Yong and Dickey, Michael D. and Genzer, Jan}, year={2014}, month={Apr} }
 @article{galvin_dimitriou_satija_genzer_2014, title={Swelling of Polyelectrolyte and Polyzwitterion Brushes by Humid Vapors}, volume={136}, ISSN={["1520-5126"]}, DOI={10.1021/ja5065334}, abstractNote={Swelling behavior of polyelectrolyte and polyzwitterion brushes derived from poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) in water vapor is investigated using a combination of neutron and X-ray reflectivity and spectroscopic ellipsometry over a wide range of relative humidity (RH) levels. The extent of swelling depends strongly on the nature of the side-chain chemistry. For parent PDMAEMA, there is an apparent enrichment of water vapor at the polymer/air interface. Despite extensive swelling at high humidity level, no evidence of charge repulsion is found in weak or strong polyelectrolyte brushes. Polyzwitterionic brushes swell to a greater extent than the quaternized brushes studied. However, for RH levels beyond 70%, the polyzwitterionic brushes take up less water molecules, leading to a decline in water volume fraction from the maximum of ~0.30 down to ~0.10. Using a gradient in polymer chain grafting density (σ), we provide evidence that this behavior stems from the formation of inter- and intramolecular zwitterionic complexes.}, number={36}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Galvin, Casey J. and Dimitriou, Michael D. and Satija, Sushil K. and Genzer, Jan}, year={2014}, month={Sep}, pages={12737–12745} }
 @article{liu_miskiewicz_escuti_genzer_dickey_2014, title={Three-dimensional folding of pre-strained polymer sheets via absorption of laser light}, volume={115}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4880160}, DOI={10.1063/1.4880160}, abstractNote={Patterned light from a laser can induce rapid self-folding of pre-strained polymer sheets. Black ink coated on the sheet absorbs the light, which converts the photon energy into thermal energy that heats the sheet locally; the temperature of the sheet is highest at the surface where the light impinges on the sheet and decreases through the sheet thickness. The gradient of temperature induces a gradient of strain relaxation through the depth of the sheet, which causes folding within seconds of irradiation. The pattern of laser light that irradiates the compositionally homogeneous two-dimensional (2D) substrate dictates the resulting three-dimensional (3D) shape. Unlike most approaches to self-folding, the methodology described here requires no patterning of pre-defined hinges. It opens up the possibility of using a patterning technique that is inherently 2D to form 3D shapes. The use of lasers also enables systematic control of key process parameters such as power, intensity, and the pattern of light (i.e., beam width and shape). The rate of folding and folding angle measured with respect to these parameters provide an indirect quantification of heat loss in the sample and thereby identify the threshold power and power intensity that must be delivered to the hinge for folding to occur.}, number={20}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Liu, Ying and Miskiewicz, Matthew and Escuti, Michael J. and Genzer, Jan and Dickey, Michael D.}, year={2014}, month={May}, pages={204911} }
 @article{oezcam_spontak_genzer_2014, title={Toward the Development of a Versatile Functionalized Silicone Coating}, volume={6}, ISSN={["1944-8252"]}, DOI={10.1021/am506661m}, abstractNote={The development of a versatile silicone copolymer coating prepared by the chemical coupling of trichlorosilane (TCS) to the vinyl groups of poly(vinylmethylsiloxane) (PVMS) is reported. The resultant PVMS-TCS copolymer can be deposited as a functional organic layer on a hydrophobic poly(dimethylsiloxane) substrate and its mechanical modulus can be regulated by varying the TCS coupling ratio. In this paper, several case studies demonstrating the versatile properties of these PVMS-TCS functional coatings on PDMS elastomer substrates are presented. Numerous experimental probes, including optical microscopy, Fourier-transform infrared spectroscopy, surface contact angle, ellipsometry, and nanoindentation, are utilized to interrogate the physical and chemical characteristics of these PVMS-TCS coatings.}, number={24}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Oezcam, A. Evren and Spontak, Richard J. and Genzer, Jan}, year={2014}, month={Dec}, pages={22544–22552} }
 @article{hardrict_gurarslan_galvin_gracz_roy_sumerlin_genzer_tonelli_2013, title={Characterizing polymer macrostructures by identifying and locating microstructures along their chains with the kerr effect}, volume={51}, ISSN={["0887-6266"]}, DOI={10.1002/polb.23248}, abstractNote={AbstractIn this brief report, we demonstrate that Kerr effect measurements, which determine the excess birefringence contributed by polymer solutes in dilute solutions observed under a strong electric field, are highly sensitive to and capable of determining their microstructures, as well as their locations along the macromolecular backbone. Specifically, using atactic triblock copolymers with the same overall composition of styrene (S) and p‐bromostyrene (pBrS) units, but with two different block arrangements, that is, pBrS90‐b‐S120‐b‐pBrS90 (I) and S60‐b‐pBrS180‐b‐S60 (II), which are indistinguishable by NMR, we detected a dramatic difference in their molar Kerr constants (mK), in agreement with those previously estimated. Although similar in magnitude, their Kerr constants differ in sign, with mK(II) positive and mK(I) negative. In addition, S/pBrS random and gradient copolymers synthesized by reversible addition‐fragmentation chain‐transfer (RAFT) polymerization exhibit a heretofore unexpected enhanced enchainment of racemic (r) pBrS‐pBrS diads. Comparison of their observed and calculated mKs suggests that the gradient S/pBrS copolymers possess an unanticipated additional gradient in stereosequence that parallels their comonomer gradient, that is, as the concentration of pBrs units decreases from one end of the copolymer chain to the other, so does the content of r diads. This conclusion could only be reached by comparison of observed and calculated Kerr effects, which access the global properties of macromolecules, and not NMR, which is only sensitive to local polymer structural environments, but not to their locations on the copolymer chains. Molar Kerr constants are characteristic of entire polymer chains and are highly sensitive to their constituent microstructures and their distribution along the chain. They may be used to both identify constituent microstructures and locate them along the polymer chain, thereby enabling, for the first time, characterization of their complete macrostructures. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013}, number={9}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Hardrict, S. N. and Gurarslan, R. and Galvin, C. J. and Gracz, H. and Roy, D. and Sumerlin, B. S. and Genzer, J. and Tonelli, A. E.}, year={2013}, month={May}, pages={735–741} }
 @article{datta_genzer_2013, title={Computer Simulation of Template Polymerization Using a Controlled Reaction Scheme}, volume={46}, ISSN={["1520-5835"]}, DOI={10.1021/ma3025915}, abstractNote={We employ a Monte Carlo simulation scheme based on the bond fluctuation model to simulate template polymerization via controlled polymerization scheme involving copolymerization of free monomers (A) and monomers bound to a template (B) that consists of linear or ring-like substrates with equidistant sites occupied by bound B monomers. Both A and B are chemically identical; i.e., there is no interaction potential acting between A and B. A new macromolecule is initiated in bulk by activation of an initiator; any monomer that is within the reaction distance (nearest neighbors) of the initiator can be incorporated into the chain. As the macromolecule grows, it adds either bulk (i.e., A) or template-bound monomers (i.e., B) to its chain. The living nature of the polymers is assured by eliminating any termination or chain transfer. We analyze the effect of the number and spacing of the B bound monomers on the substrate on the chemical composition and monomer distribution in the resultant A–B random copolymer. Our results reveal that the likelihood of B being incorporated in the A–B copolymer increases with increasing the number and density of the B monomers on the template substrate; the maximum sequence length of "polymerized" bound B monomers increases with increasing the number of bound B monomers present in a single substrate. Long consecutive sequences of B bound monomers in the A–B copolymer are formed when the B bound monomers are immobilized in space in high densities.}, number={6}, journal={MACROMOLECULES}, author={Datta, Preeta and Genzer, Jan}, year={2013}, month={Mar}, pages={2474–2484} }
 @article{malik_hall_genzer_2013, title={Effect of Protein-like Copolymers Composition on the Phase Separation Dynamics of a Polymer Blend: A Monte Carlo Simulation}, volume={46}, ISSN={["1520-5835"]}, DOI={10.1021/ma400187u}, abstractNote={We use kinetic Monte Carlo simulation based on the bond fluctuation model to investigate the dynamics of phase separation in immiscible 80/20 A/B binary polymer blends, comprising 80% and 20% of A and B components, respectively, in the presence of ≈4.92% 30-mer protein-like copolymer (PLC) made of C and D segments. The molecular interactions are chosen such that there is an attraction between A and C and between B and D segments and no interaction between like segments; all other interaction energies have been chosen to be repulsive. The PLC migration to and presence at the A/B interface effectively slow down the process of phase separation in binary blends, thereby minimizing the unfavorable A/B contacts and reducing the A/B interfacial tension. The ability of PLCs to effectively retard the process of phase separation depends sensitively on the PLC composition. PLCs with 0.3 ≤ xC ≤ 0.5, where xC is the mole fraction of C, are most effective in compatibilizing the 80/20 A/B binary blend. The growth of pha...}, number={10}, journal={MACROMOLECULES}, author={Malik, Ravish and Hall, Carol K. and Genzer, Jan}, year={2013}, month={May}, pages={4207–4214} }
 @article{goli_gera_liu_rao_rojas_genzer_2013, title={Generation and Properties of Antibacterial Coatings Based on Electrostatic Attachment of Silver Nanoparticles to Protein-Coated Polypropylene Fibers}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am4011644}, abstractNote={We present a simple method for attaching silver nanoparticles to polypropylene (PP) fibers in a two-step process to impart antibacterial properties. Specifically, PP fibers are pretreated by the adsorption from an aqueous solution of heat-denatured lysozyme (LYS) followed by LYS cross-linking using glutaraldehyde and sodium borohydride. At neutral pH, the surface of the adsorbed LYS layer is enriched with numerous positive charges. Silver nanoparticles (AgNPs) capped with trisodium citrate are subsequently deposited onto the protein-coated PP. Nanoparticle binding is mediated by electrostatic interactions between the positively charged LYS layer and the negatively charged AgNPs. The density of AgNPs deposited on PP depends on the amount of protein adsorbed on the surface. UV-vis spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy are employed to follow all preparation steps and to characterize the resulting functional surfaces. The antibacterial activity of the modified surfaces is tested against gram negative bacteria Escherichia coli (E. coli). Overall, our results show that PP surfaces coated with AgNPs exhibit excellent antibacterial activity with 100% removal efficiency.}, number={11}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Goli, Kiran K. and Gera, Nimish and Liu, Xiaomeng and Rao, Balaji M. and Rojas, Orlando J. and Genzer, Jan}, year={2013}, month={Jun}, pages={5298–5306} }
 @article{bain_turgman-cohen_genzer_2013, title={Macromol. Theory Simul. 1/2013}, volume={22}, ISSN={1022-1344}, url={http://dx.doi.org/10.1002/mats.201370001}, DOI={10.1002/mats.201370001}, abstractNote={Cover: Polymerizations in confined geometries result in deviations from predicted properties, including molecular weight distribution, topology, and composition. Similar effects are encountered in surface-initiated polymerizations, where confinement arises from grafting of chain ends. Recent developments in computer simulations of bulk, confined, and surface-initiated polymerizations are reviewed, and the cover image compares systems with varying degrees of confinement and analogous surface-initiated examples. Further details can be found in the article by E. D. Bain, S. Turgman-Cohen, J. Genzer* on page 8.}, number={1}, journal={Macromolecular Theory and Simulations}, publisher={Wiley}, author={Bain, Erich D. and Turgman-Cohen, Salomon and Genzer, Jan}, year={2013}, month={Jan}, pages={1–1} }
 @article{mays_dickey_genzer_2013, title={Microfluidic channels fabricated from poly(vinylmethylsiloxane) networks that resist swelling by organic solvents}, volume={13}, ISSN={["1473-0189"]}, DOI={10.1039/c3lc50848j}, abstractNote={This paper describes the use of poly(vinylmethylsiloxane) (PVMS) networks for fabricating microfluidic channels that resist swelling in the presence of organic solvents, thus providing a versatile alternative to poly(dimethylsiloxane) (PDMS). In particular, we demonstrate that in contrast to PDMS microchannels, the UV-treated PVMS structures exhibit high resistance to swelling by toluene.}, number={22}, journal={LAB ON A CHIP}, publisher={Royal Society of Chemistry (RSC)}, author={Mays, Robin L. and Dickey, Michael D. and Genzer, Jan}, year={2013}, pages={4317–4320} }
 @article{kopyshev_galvin_genzer_lomadze_santer_2013, title={Opto-Mechanical Scission of Polymer Chains in Photosensitive Diblock-Copolymer Brushes}, volume={29}, ISSN={["0743-7463"]}, DOI={10.1021/la403241t}, abstractNote={In this paper we report on an opto-mechanical scission of polymer chains within photosensitive diblock-copolymer brushes grafted to flat solid substrates. We employ surface-initiated polymerization of methylmethacrylate (MMA) and t-butyl methacrylate (tBMA) to grow diblock-copolymer brushes of poly(methylmethacrylate-b-t-butyl methacrylate) following the atom transfer polymerization (ATRP) scheme. After the synthesis, deprotection of the PtBMA block yields poly(methacrylic acid) (PMAA). To render PMMA-b-PMAA copolymers photosensitive, cationic azobenzene containing surfactants are attached to the negatively charged outer PMAA block. During irradiation with an ultraviolet (UV) interference pattern, the extent of photoisomerization of the azobenzene groups varies spatially and results in a topography change of the brush, i.e., formation of surface relief gratings (SRG). The SRG formation is accompanied by local rupturing of the polymer chains in areas from which the polymer material recedes. This opto-mechanically induced scission of the polymer chains takes place at the interfaces of the two blocks and depends strongly on the UV irradiation intensity. Our results indicate that this process may be explained by employing classical continuum fracture mechanics, which might be important for tailoring the phenomenon for applying it to poststructuring of polymer brushes.}, number={45}, journal={LANGMUIR}, author={Kopyshev, Alexey and Galvin, Casey J. and Genzer, Jan and Lomadze, Nino and Santer, Svetlana}, year={2013}, month={Nov}, pages={13967–13974} }
 @article{efimenko_oezcam_genzer_fischer_phelan_douglas_2013, title={Self-assembly fronts in collision: impinging ordering organosilane layers}, volume={9}, ISSN={["1744-6848"]}, DOI={10.1039/c2sm27600c}, abstractNote={Colliding autocatalytic wave-fronts of self-assembling organosilane (OS) layers are generated through the controlled positioning of sources of the volatile OS material at the edges of a silica wafer and through adjustment of the container dimensions in which the wafer sources are placed. The concentration profiles and molecular orientation of the OS colliding wave-fronts are assessed by means of combinatorial near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. For systems involving self-assembly wave-fronts developing from the same OS precursor molecule, the shapes of interfacial region arising from front collision are centro-symmetrical and slowly ‘heal’ to form a uniform OS layer. In contrast, heterogeneous systems, involving OS molecules having different chemistries exhibit different rates of advance and highly non-symmetrical concentration profiles after front collision. We discuss the general nature of our OS colliding front data in terms of a mean field model of colliding reaction–diffusion fronts that generalizes a model introduced before for describing single OS front propagation.}, number={8}, journal={SOFT MATTER}, author={Efimenko, Kirill and Oezcam, Ali E. and Genzer, Jan and Fischer, Daniel A. and Phelan, Fredrick R., Jr. and Douglas, Jack F.}, year={2013}, pages={2493–2505} }
 @article{casper_gözen_dickey_genzer_maria_2013, title={Surface wrinkling by chemical modification of poly(dimethylsiloxane)-based networks during sputtering}, volume={9}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/C3SM50966D}, DOI={10.1039/C3SM50966D}, abstractNote={Wrinkling is an important mechanical phenomenon that generates periodic topographical patterns across a surface. This paper presents experimental evidence that surface wrinkles, which form consequent to thin film magnetron sputtering of either indium tin oxide (ITO) or aluminum on poly(dimethylsiloxane) networks (PDMS-N) made from a commercial Sylgard-184 kit, result from chemical modification of the PDMS-N surface as opposed to extrinsic thermomechanical stresses originating from differential thermal expansion. X-ray photoelectron spectroscopy results reveal that the PDMS-N surface becomes depleted in carbon and concurrently enriched in oxygen relative to silicon due to sputtering. This silica-like surface layer possesses intrinsic compressive stress that leads to wrinkle formation during the first ≈5 seconds of sputtering. The wrinkles maintain their periodicity irrespective of the thickness of the ITO film formed during subsequent deposition. Furthermore, upon removal of the ITO layer, the wrinkles persist with their periodicity unchanged. A narrow sputtering pressure window between 2 and 12 mTorr generates wrinkles. Pressures below this range cannot sustain a radio frequency plasma, while pressures above this range provide sufficient thermalization of kinetic energy as to eliminate the energetic bombardment that modifies the PDMS-N. This study provides a new understanding of the origins of wrinkling in sputtered films on polymeric substrates and creates opportunities to manipulate the topography produced by spontaneous surface wrinkling.}, number={32}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Casper, Michelle D. and Gözen, Arif Ö. and Dickey, Michael D. and Genzer, Jan and Maria, Jon-Paul}, year={2013}, pages={7797} }
 @article{salas_genzer_lucia_hubbe_rojas_2013, title={Water-Wettable Polypropylene Fibers by Facile Surface Treatment Based on Soy Proteins}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am401065t}, abstractNote={Modification of the wetting behavior of hydrophobic surfaces is essential in a variety of materials, including textiles and membranes that require control of fluid interactions, adhesion, transport processes, sensing, etc. This investigation examines the enhancement of wettability of an important class of textile materials, viz., polypropylene (PP) fibers, by surface adsorption of different proteins from soybeans, including soy flour, isolate,glycinin, and β-conglycinin. Detailed investigations of soy adsorption from aqueous solution (pH 7.4, 25 °C) on polypropylene thin films is carried out using quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). A significant amount of protein adsorbs onto the PP surfaces primarily due to hydrophobic interactions. We establish that adsorption of a cationic surfactant, dioctadecyldimethylammonium bromide (DODA) onto PP surfaces prior to the protein deposition dramatically enhances its adsorption. The adsorption of proteins from native (PBS buffer, pH 7.4, 25 °C) and denatured conditions (PBS buffer, pH 7.4, 95 °C) onto DODA-treated PP leads to a high coverage of the proteins on the PP surface as confirmed by a significant improvement in water wettability. A shift in the contact angle from 128° to completely wettable surfaces (≈0°) is observed and confirmed by imaging experiments conducted with fluorescence tags. Furthermore, the results from wicking tests indicate that hydrophobic PP nonwovens absorb a significant amount of water after protein treatment, i.e., the PP-modified surfaces become completely hydrophilic.}, number={14}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Salas, Carlos and Genzer, Jan and Lucia, Lucian A. and Hubbe, Martin A. and Rojas, Orlando J.}, year={2013}, month={Jul}, pages={6541–6548} }
 @article{salas_rojas_lucia_hubbe_genzer_2012, title={Adsorption of Glycinin and beta-Conglycinin on Silica and Cellulose: Surface Interactions as a Function of Denaturation, pH, and Electrolytes}, volume={13}, ISSN={["1526-4602"]}, DOI={10.1021/bm2014153}, abstractNote={Soybean proteins have found uses in different nonfood applications due to their interesting properties. We report on the kinetics and extent of adsorption on silica and cellulose surfaces of glycinin and β-conglycinin, the main proteins present in soy. Quartz crystal microgravimetry (QCM) experiments indicate that soy protein adsorption is strongly affected by changes in the physicochemical environment. The affinity of glycinin and the mass adsorbed on silica and cellulose increases (by ca. 13 and 89%, respectively) with solution ionic strength (as it increases from 0 to 100 mM NaCl) due to screening of electrostatic interactions. In contrast, β-conglycinin adsorbs on the same substrates to a lower extent and the addition of electrolyte reduces adsorption (by 25 and 57%, respectively). The addition of 10 mM 2-mercaptoethanol, a denaturing agent, reduces the adsorption of both proteins with a significant effect for glycinin. This observation is explained by the cleavage of disulfide bonds which allows unfolding of the molecules and promotes dissociation into subunits that favors more compact adsorbed layer structures. In addition, adsorption of glycinin onto cellulose decreases with lowering the pH from neutral to pH 3 due to dissociation of the macromolecules, resulting in flatter adsorbed layers. The respective adsorption isotherms fit a Langmuir model and QCM shifts in energy dissipation and frequency reveal multiple-step kinetic processes indicative of changes in adlayer structure.}, number={2}, journal={BIOMACROMOLECULES}, author={Salas, Carlos and Rojas, Orlando J. and Lucia, Lucian A. and Hubbe, Martin A. and Genzer, Jan}, year={2012}, month={Feb}, pages={387–396} }
 @article{turgman-cohen_genzer_2012, title={Computer Simulation of Concurrent Bulk- and Surface-Initiated Living Polymerization}, volume={45}, ISSN={["0024-9297"]}, DOI={10.1021/ma202679r}, abstractNote={We use Monte Carlo simulation implementing the bond fluctuation model formalism in the canonical (NVT) ensemble to study living polymerization initiated concurrently in bulk and on flat substrates. Our results reveal that the molecular weights and molecular weight distributions of both classes of polymers depend on the grafting density of the surface-bound polymers (σ) and the fraction of polymers on the surface (η) relative to that in bulk. In general, polymer grafts on the surface possess lower molecular weight and higher polydispersity index compared to their bulk counterparts. The difference between the molecular weight of the two populations of polymers decreases with decreasing σ and increasing η. Our work provides evidence that the common practice of using the molecular weight of bulk-initiated polymers in estimating the grafting density of polymeric anchors on flat substrates is not generally valid.}, number={4}, journal={MACROMOLECULES}, author={Turgman-Cohen, Salomon and Genzer, Jan}, year={2012}, month={Feb}, pages={2128–2137} }
 @article{powers_ryu_jhon_strickland_hall_genzer_2012, title={Determining the Polydispersity in Chemical Composition and Monomer Sequence Distribution in Random Copolymers Prepared by Postpolymerization Modification of Homopolymers}, volume={1}, ISSN={["2161-1653"]}, DOI={10.1021/mz300386g}, abstractNote={We report on establishing the polydispersity in chemical composition (PCC) and polydispersity in monomer sequence distribution (PMSD) in random copolymers of poly(styrene-co-4-bromostyrene) (PBrxS), where x = (0.385 ± 0.035) is the mole fraction of the 4-bromostyrene units (4-BrS), prepared by electrophilic substitution of bromine in the para-position of the phenyl ring of the parent polystyrene. Upon fixing the total number of repeating units, we tune the distribution of styrene and 4-BrS segments in PBrxS by carrying out the bromination reaction on polystyrene homopolymers in different solvents. While PBrxS with relatively random comonomer distribution is prepared in 1-chlorodecane, random-blocky sequences of 4-BrS in PBrxS are achieved by carrying out the bromination reaction in 1-chlorododecane. The PCC in both copolymers is established by fractionating both polymers using interaction chromatography (IC) and determining the chemical composition of the individual fractions by neutron activation analysis (NAA). The NAA data along with IC experiments reveal that the random-blocky sample possesses a narrowed PCC relative to a specimen with a more random comonomer sequence distribution. The full width at half-maximum (fwhm) in the chemical composition profile from IC is used to quantify PCC; the random mother sample possessed a 25% fwhm, while the random blocky mother sample has a fwhm equal to 8.7%. The change in the adsorption enthalpy per brominated segment due to adsorption is determined to be ≈1.5 times greater for the random-blocky than the relatively random sample, proving that more pronounced cooperative adsorption occurs in the case of the random-blocky sample relative to the random copolymer sample. Computer simulation employing the discontinuous molecular dynamic scheme further reveals that the distribution of comonomer sequences, that is, PMSD, in the random-blocky copolymer is narrower than that in the copolymer with a random distribution of both monomers.}, number={9}, journal={ACS MACRO LETTERS}, author={Powers, Wayne and Ryu, Chang Y. and Jhon, Young K. and Strickland, Lawrence A. and Hall, Carol K. and Genzer, Jan}, year={2012}, month={Sep}, pages={1128–1133} }
 @article{goli_rojas_genzer_2012, title={Formation and Antifouling Properties of Amphiphilic Coatings on Polypropylene Fibers}, volume={13}, ISSN={1525-7797 1526-4602}, url={http://dx.doi.org/10.1021/bm301223b}, DOI={10.1021/bm301223b}, abstractNote={We describe the formation of amphiphilic polymeric assemblies via a three-step functionalization process applied to polypropylene (PP) nonwovens and to reference hydrophobic self-assembled n-octadecyltrichlorosilane (ODTS) monolayer surfaces. In the first step, denatured proteins (lysozyme or fibrinogen) are adsorbed onto the hydrophobic PP or the ODTS surfaces, followed by cross-linking with glutaraldehyde in the presence of sodium borohydride (NaBH(4)). The hydroxyl and amine functional groups of the proteins permit the attachment of initiator molecules, from which poly (2-hydroxyethyl methacrylate) (PHEMA) polymer grafts are grown directly through "grafting from" atom transfer radical polymerization. The terminal hydroxyls of HEMA's pendent groups are modified with fluorinating moieties of different chain lengths, resulting in amphiphilic brushes. A palette of analytical tools, including ellipsometry, contact angle goniometry, Fourier transform infrared spectroscopy in the attenuated total reflection mode, and X-ray photoelectron spectroscopy is employed to determine the changes in physicochemical properties of the functionalized surfaces after each modification step. Antifouling properties of the resultant amphiphilic coatings on PP are analyzed by following the adsorption of fluorescein isothiocyanate-labeled bovine serum albumin as a model fouling protein. Our results suggest that amphiphilic coatings suppress significantly adsorption of proteins as compared with PP fibers or PP surfaces coated with PHEMA brushes. The type of fluorinated chain grafted to PHEMA allows modulation of the surface composition of the topmost layer of the amphiphilic coating and its antifouling capability.}, number={11}, journal={Biomacromolecules}, publisher={American Chemical Society (ACS)}, author={Goli, Kiran K. and Rojas, Orlando J. and Genzer, Jan}, year={2012}, month={Oct}, pages={3769–3779} }
 @article{goli_rojas_oezcam_genzer_2012, title={Generation of Functional Coatings on Hydrophobic Surfaces through Deposition of Denatured Proteins Followed by Grafting from Polymerization}, volume={13}, ISSN={["1525-7797"]}, DOI={10.1021/bm300075u}, abstractNote={Hydrophilic coatings were produced on flat hydrophobic substrates featuring n-octadecyltrichlorosilane (ODTS) and synthetic polypropylene (PP) nonwoven surfaces through the adsorption of denatured proteins. Specifically, physisorption from aqueous solutions of α-lactalbumin, lysozyme, fibrinogen, and two soy globulin proteins (glycinin and β-conglycinin) after chemical (urea) and thermal denaturation endowed the hydrophobic surfaces with amino and hydroxyl functionalities, yielding enhanced wettability. Proteins adsorbed strongly onto ODTS and PP through nonspecific interactions. The thickness of adsorbed heat-denatured proteins was adjusted by varying the pH, protein concentration in solution, and adsorption time. In addition, the stability of the immobilized protein layer was improved significantly after interfacial cross-linking with glutaraldehyde in the presence of sodium borohydride. The amino and hydroxyl groups present on the protein-modified surfaces served as reactive sites for the attachment of polymerization initiators from which polymer brushes were grown by surface-initiated atom-transfer radical polymerization of 2-hydroxyethyl methacrylate. Protein denaturation and adsorption as well as the grafting of polymeric brushes were characterized by circular dichroism, ellipsometry, contact angle, and Fourier transform infrared spectroscopy in the attenuated total reflection mode.}, number={5}, journal={BIOMACROMOLECULES}, author={Goli, Kiran K. and Rojas, Orlando J. and Oezcam, A. Evren and Genzer, Jan}, year={2012}, month={May}, pages={1371–1382} }
 @article{oezcam_roskov_spontak_genzer_2012, title={Generation of functional PET microfibers through surface-initiated polymerization}, volume={22}, ISSN={["1364-5501"]}, DOI={10.1039/c2jm16017j}, abstractNote={In this study, we report on a facile and robust method by which poly(ethylene terephthalate) (PET) surfaces can be chemically modified with functional polymer brushes while avoiding chemical degradation. The surface of electrospun PET microfibers has been functionalized by growing poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) brushes through a multi-step chemical sequence that ensures retention of mechanically robust microfibers. Polymer brushes are grown via “grafting from” atom-transfer radical polymerization after activation of the PET surface with 3-aminopropyltriethoxysilane. Spectroscopic analyses confirm the expected reactions at each reaction step, as well as the ultimate growth of brushes on the PET microfibers. Post-polymerization modification reactions have likewise been conducted to further functionalize the brushes and impart surface properties of biomedical interest on the PET microfibers. Antibacterial activity and protein resistance of PET microfibers functionalized with PDMAEMA and PHEMA brushes, respectively, are demonstrated, thereby making these surface-modified PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring mechanically robust support media.}, number={12}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Oezcam, A. Evren and Roskov, Kristen E. and Spontak, Richard J. and Genzer, Jan}, year={2012}, pages={5855–5864} }
 @article{gallow_jhon_genzer_loo_2012, title={Influence of gradient strength and composition profile on the onset of the cloud point transition in hydroxyethyl methacrylate/dimethylaminoethyl methacrylate gradient copolymers}, volume={53}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2012.01.027}, abstractNote={We examined the onset of the cloud point in dilute aqueous solutions of gradient copolymers of 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate. Dynamic Light Scattering (DLS) and transmittance measurements both indicate that the copolymer solution cloud point decreases with increasing copolymer gradient strength, defined as the largest difference in the instantaneous composition along the copolymer. While transmittance measurements suggest that macroscopic clouding does not set in until 30% of the polymer chain becomes insoluble, DLS experiments, which are more sensitive to the onset of aggregation, indicate that the onset of aggregation occurs at the point where the least soluble polymer chain end becomes insoluble. Collectively, our data indicate that the macroscopic cloud point transition is highly sensitive to co-monomer sequence distribution of the copolymers, with its onset and transition breadth tunable through copolymer gradient strength.}, number={5}, journal={POLYMER}, author={Gallow, Keith C. and Jhon, Young K. and Genzer, Jan and Loo, Yueh-Lin}, year={2012}, month={Feb}, pages={1131–1137} }
 @article{gozen_genzer_spontak_2012, title={Interfacial stabilization of bilayered nanolaminates by asymmetric block copolymers}, volume={100}, ISSN={["0003-6951"]}, DOI={10.1063/1.3692102}, abstractNote={Block copolymers are macromolecular surfactants that self-assemble into a variety of nanostructural elements or reduce the interfacial tension between incompatible polymers. Here, we examine the ability of diblock copolymers differing in composition to stabilize bilayered homopolymer nanolaminates on flat solid supports. In this arrangement, self-assembly competes with interfacial modification and, in one case, promotes destabilization of the top film. To discern the corresponding mechanism, we investigate nanolaminates with a thin copolymer layer positioned between the homopolymer layers. Stabilization commences when this middle layer is sufficiently thick so that the block that is miscible with the top layer forms a brush.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Gozen, Arif O. and Genzer, Jan and Spontak, Richard J.}, year={2012}, month={Mar} }
 @article{peng_efimenko_genzer_parsons_2012, title={Oligomer Orientation in Vapor-Molecular-Layer-Deposited Alkyl-Aromatic Polyamide Films}, volume={28}, ISSN={["0743-7463"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000306441100019&KeyUID=WOS:000306441100019}, DOI={10.1021/la3017936}, abstractNote={The surface-limited molecular-layer deposition of alkyl-aromatic polyamide films using sequential doses of 1,4-butane diamine (BDA) and terephthaloyl dichloride (TDC) is characterized using in situ quartz crystal microbalance and ex situ spectroscopy analysis. For the first time, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to offer insight into molecular orientation in films deposited via molecular-layer deposition (MLD). The results show that the oligomer units are lying nearly parallel to the surface, which differs from the linear vertical growth mode often used to illustrate film growth.}, number={28}, journal={LANGMUIR}, author={Peng, Qing and Efimenko, Kirill and Genzer, Jan and Parsons, Gregory N.}, year={2012}, month={Jul}, pages={10464–10470} }
 @article{salas_rojas_lucia_hubbe_genzer_2013, title={On the Surface Interactions of Proteins with Lignin}, volume={5}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/am3024788}, DOI={10.1021/am3024788}, abstractNote={Lignins are used often in formulations involving proteins but little is known about the surface interactions between these important biomacromolecules. In this work, we investigate the interactions at the solid-liquid interface of lignin with the two main proteins in soy, glycinin (11S) and β-conglycinin (7S). The extent of adsorption of 11S and 7S onto lignin films and the degree of hydration of the interfacial layers is quantified via Quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR). Solution ionic strength and protein denaturation (2-mercaptoethanol and urea) critically affect the adsorption process as protein molecules undergo conformational changes and their hydrophobic or hydrophilic amino acid residues interact with the surrounding medium. In general, the adsorption of the undenatured proteins onto lignin is more extensive compared to that of the denatured biomolecules and a large amount of water is coupled to the adsorbed molecules. The reduction in water contact angle after protein adsorption (by ~40° and 35° for undenatured 11S and 7S, respectively) is explained by strong nonspecific interactions between soy proteins and lignin.}, number={1}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Salas, Carlos and Rojas, Orlando J. and Lucia, Lucian A. and Hubbe, Martin A. and Genzer, Jan}, year={2013}, month={Jan}, pages={199–206} }
 @article{pandav_pryamitsyn_gallow_loo_genzer_ganesan_2012, title={Phase behavior of gradient copolymer solutions: a Monte Carlo simulation study}, volume={8}, ISSN={["1744-6848"]}, DOI={10.1039/c2sm25577d}, abstractNote={We use computer simulations to study the phase separation behavior of amphiphilic linear gradient copolymer solution under poor solvent conditions. Using the bond fluctuation model and parallel tempering algorithm, we explore the influence of the gradient strength (the largest difference in the instantaneous composition along the copolymer) upon the phase separation characteristics. Under poor solvent conditions, the chains collapse to form micelle-like aggregates. We find that the critical temperature for this transition exhibits a linear dependence on the gradient strength of the copolymers. A systematic quantification of the cluster characteristics formed during the phase separation also reveals a strong dependence of aggregation numbers and the bridging statistics upon the gradient strength of the copolymers. Analysis of our results reveals that the critical parameter determining the thermodynamic behavior of gradient copolymers is in fact the average length of the hydrophobic sequences in the gradient copolymers. We demonstrate that the latter provides a useful measure to quantitatively predict the critical transition temperature of the gradient copolymer solution. We also present a few results from the framework of an annealed representation of the sequences of the gradient copolymer to demonstrate the limitations arising from such a model representation.}, number={24}, journal={SOFT MATTER}, author={Pandav, Gunja and Pryamitsyn, Victor and Gallow, Keith C. and Loo, Yueh-Lin and Genzer, Jan and Ganesan, Venkat}, year={2012}, pages={6471–6482} }
 @misc{bain_turgman-cohen_genzer_2013, title={Progress in Computer Simulation of Bulk, Confined, and Surface-initiated Polymerizations}, volume={22}, ISSN={["1521-3919"]}, DOI={10.1002/mats.201200030}, abstractNote={AbstractIn this article we provide a brief summary of computational techniques applied to investigate polymerization reactions in general, with a focus on systems under confinement and initiated from surfaces. We concentrate on two major classes of techniques, i.e., stochastic methods and molecular modeling. We describe the major principles of the two classes of methodologies and point out their strengths and weaknesses. We review a variety of studies from the literature and conclude with an outlook of these two classes of computer simulation approaches as they are applied to “grafting from” polymerizations. magnified image}, number={1}, journal={MACROMOLECULAR THEORY AND SIMULATIONS}, author={Bain, Erich D. and Turgman-Cohen, Salomon and Genzer, Jan}, year={2013}, month={Jan}, pages={8–30} }
 @article{ozcam_roskov_genzer_spontak_2012, title={Responsive PET Nano/Microfibers via Surface-Initiated Polymerization}, volume={4}, ISSN={["1944-8252"]}, DOI={10.1021/am201559f}, abstractNote={Poly(ethylene terephthalate) (PET) is one of the most important thermoplastics in ubiquitous use today because of its mechanical properties, clarity, solvent resistance, and recyclability. In this work, we functionalize the surface of electrospun PET microfibers by growing poly(N-isopropylacrylamide) (PNIPAAm) brushes through a chemical sequence that avoids PET degradation to generate thermoresponsive microfibers that remain mechanically robust. Amidation of deposited 3-aminopropyltriethoxysilane, followed by hydrolysis, yields silanol groups that permit surface attachment of initiator molecules, which can be used to grow PNIPAAm via "grafting from" atom-transfer radical polymerization. Spectroscopic analyses performed after each step confirm the expected reaction and the ultimate growth of PNIPAAm brushes. Water contact-angle measurements conducted at temperatures below and above the lower critical solution temperature of PNIPAAm, coupled with adsorption of Au nanoparticles from aqueous suspension, demonstrate that the brushes retain their reversible thermoresponsive nature, thereby making PNIPAAm-functionalized PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring robust microfibers.}, number={1}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ozcam, A. Evren and Roskov, Kristen E. and Genzer, Jan and Spontak, Richard J.}, year={2012}, month={Jan}, pages={59–64} }
 @book{genzer_2012, title={Soft matter gradient surfaces: methods and applications}, DOI={10.1002/9781118166086}, abstractNote={Contributors vii Preface xi 1 Gradient Libraries: Harnessing a Ubiquitous Phenomenon to Accelerate Experimentation 1 Michael J. Fasolka 2 Classification of Key Attributes of Soft Material Gradients 19 Jan Genzer and Rajendra R. Bhat 3 Discovery and Optimization of Sensing Materials Using Discrete and Gradient Arrays 47 Radislav A. Potyrailo 4 Colliding Self-Assembly Waves in Organosilane Monolayers 93 Kirill Efimenko, Ali E. Ozcam, Jan Genzer, Daniel A. Fischer, Fredrick R. Phelan, and Jack F. Douglas 5 Orientational Anchoring of Liquid Crystals on Surfaces Presenting Continuous Gradients in Composition 109 Jugal K. Gupta, Kirill Efimenko, Daniel A. Fischer, Jan Genzer, and Nicholas L. Abbott 6 Continuous Infusion Microchannel Approach to Generate Composition Gradients from Viscous Polymer Solutions 129 Pratyay Basak, Pedro Zapata, Keith Reed, Ismael Gomez, and J. Carson Meredith 7 Gradient Assembly of Complex Surfaces for Sensing, Fabrication, and High Throughput Analysis 145 Andrew C. Hillier 8 Making Gradient Patterns by Electron-Beam Chemical Lithography with Monomolecular Resists 199 Nirmalya Ballav, Andreas Terfort, and Michael Zharnikov 9 Electrochemical Mapping for Polymer Chemical and Physical Gradients 229 Roger H. Terrill, Xuejun Wang, and Paul W. Bohn 10 Directed Assembly of Block Copolymer Films: Effects of Rough Substrates and Thermal Fields 257 Manish M. Kulkarni, Alamgir Karim, and Kevin G. Yager 11 Hydrogel Gradients by Self-Initiated Photografting and Photopolymerization: Preparation, Characterization, and Protein Interactions 279 Tobias Ekblad, Andreas Larsson, and Bo Liedberg 12 Polymer Gradients: Responsive Grafted Layers 303 Igor Luzinov and Sergiy Minko 13 Bioactive Self-Assembled Monolayer Gradients 329 Nicole M. Moore and Matthew L. Becker 14 Morphology Gradients on Different Size Scales and Their Application in Biological Studies 365 Christian Zink and Nicholas D. Spencer 15 Molecularly Defined Peptide Spacing Gradients for Cell Guidance 383 Vera C. Hirschfeld-Warneken and Joachim P. Spatz 16 Motion of Drops on Gradient Surfaces 407 R. Shankar Subramanian Index 431}, publisher={Hoboken, N.J.: Wiley}, author={Genzer, Jan}, year={2012} }
 @article{genzer_2012, title={Surface-Bound Gradients for Studies of Soft Materials Behavior}, volume={42}, ISSN={["1531-7331"]}, DOI={10.1146/annurev-matsci-070511-155050}, abstractNote={ We provide a succinct account of surface-bound gradient structures created from soft materials or those facilitating the study of soft materials behavior. We commence by classifying the chief attributes of gradient structures and offer a few examples of fabrication methods employed to generate such structures. We then illustrate the versatility of gradient assemblies in functioning as recording media for monitoring a physico-chemical process, facilitating fast screening of physico-chemical phenomena, and playing an important part in the design and fabrication of surface-anchored molecular and macromolecular engines for the directed transport of soft materials. }, journal={ANNUAL REVIEW OF MATERIALS RESEARCH, VOL 42}, author={Genzer, Jan}, year={2012}, pages={435–468} }
 @article{bain_dawes_oezcam_hu_gorman_srogl_genzer_2012, title={Surface-Initiated Polymerization by Means of Novel, Stable, Non-Ester-Based Radical Initiator}, volume={45}, ISSN={["1520-5835"]}, DOI={10.1021/ma300491e}, abstractNote={A novel, ester-free initiator for surface-initiated free radical polymerization has been synthesized and tested. The structurally non-symmetrical azo-based initiator features a chemically stable alkane linker between the initiating group and the silane anchoring group, setting it apart from the majority of surface initiators that are linked by hydrolyzable moieties, such as esters. The novel design of the initiator is bolstered by an original synthetic approach, leading to a greater yield and a dramatic reduction in cyanide usage relative to previous methods. Here we demonstrate the capability of this novel initiator for surface-initiated free radical polymerization (SI-FRP), reverse ATRP, and RAFT, noting that Arrhenius behavior of SI-FRP differs significantly from that of FRP in the bulk. Furthermore, we show that polymer brushes formed from the novel initiator are more stable than those formed from ester-based initiators.}, number={9}, journal={MACROMOLECULES}, author={Bain, Erich D. and Dawes, Keith and Oezcam, A. Evren and Hu, Xinfang and Gorman, Christopher B. and Srogl, Jiri and Genzer, Jan}, year={2012}, month={May}, pages={3802–3815} }
 @article{datta_efimenko_genzer_2012, title={The effect of confinement on thermal frontal polymerization}, volume={3}, ISSN={["1759-9954"]}, DOI={10.1039/c2py20640d}, abstractNote={In thermal frontal polymerization, the interplay between heat diffusion and Arrhenius type reaction kinetics gives rise to a propagating reactive front that is effectively sustained through a system positive feedback mechanism. We seek to understand how spatial confinement affects the system dynamics and overall polymerization kinetics. We find that with increasing confinement of the system, the front propagation velocity decreases and the nearly “parabolic” front profile flattens out. While in bulk or unconfined systems the convective heat and mass transfer effects are responsible for higher heat generation rates and higher temperature gradients, leading to faster front propagation, the convection is significantly suppressed in highly confined systems. Consequently, a smaller number of radicals are generated, resulting in a slower propagation step and long polymer chains.}, number={12}, journal={POLYMER CHEMISTRY}, author={Datta, Preeta and Efimenko, Kirill and Genzer, Jan}, year={2012}, month={Dec}, pages={3243–3246} }
 @article{mays_pourhossein_savithri_genzer_chiechi_dickey_2013, title={Thiol-containing polymeric embedding materials for nanoskiving}, volume={1}, ISSN={["2050-7534"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879924924&partnerID=MN8TOARS}, DOI={10.1039/c2tc00030j}, abstractNote={This paper describes the characterization of new embedding resins for nanoskiving (ultramicrotomy) that contain thiols. Nanoskiving is a technique to produce nanoscale structures using an ultramicrotome to section thin films of materials (e.g., gold) embedded in polymer. Epoxies are used typically as embedding resins for microtomy. Epoxies, however, do not adhere well to gold or other smooth metallic structures that are used commonly for nanoskiving. Thiol–ene and thiol–epoxy polymers provide improved adhesion to gold due to the thiol functional group. In addition, the thiol–ene polymers can be prepared within minutes using photopolymerization, which allows for rapid prototyping. Two commercial thiol-containing adhesives were evaluated as resins in addition to several formulations of commercially available monomers. The important physical and mechanical properties for microtomy of these unconventional embedding resins were characterized and the properties were compared to commercial epoxy resins. Gold nanowires were fabricated using nanoskiving of gold films embedded in these unconventional resins. These studies show that a 3 : 4 mixture of thiol (pentaerythritol tetra(3-mercaptopropionate)) and ene (triallyl-1,3,5-triazine-2,4,6-trione) works very well as a resin for nanoskiving and provides improved adhesion and reduced preparation time relative to epoxies.}, number={1}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, publisher={Royal Society of Chemistry (RSC)}, author={Mays, Robin L. and Pourhossein, Parisa and Savithri, Dhanalekshmi and Genzer, Jan and Chiechi, Ryan C. and Dickey, Michael D.}, year={2013}, pages={121–130} }
 @article{liu_vesterinen_genzer_seppala_rojas_2011, title={Adsorption of PEO-PPO-PEO Triblock Copolymers with End-Capped Cationic Chains of Poly(2-dimethylaminoethyl methacrylate)}, volume={27}, ISSN={["0743-7463"]}, DOI={10.1021/la201596x}, abstractNote={We study the adsorption of a symmetric triblock copolymer of ethylene oxide, EO, and propylene oxide, PO, end-capped with quarternized poly(2-dimethylaminoethyl methacrylate), DMAEMA (DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24)). Light scattering and tensiometry are used to measure the relative size of the associated structures and surface excess at the air-liquid interface. The adsorbed amount, the amount of coupled water, and the viscoelasticity of the adsorbed polymer layer are measured on hydrophobic and hydrophilic surfaces (polypropylene, cellulose, and silica) by using quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR) at different ionic strengths and temperatures. The results of the experiments are compared with those obtained after adsorption of the uncharged precursor copolymer, without the cationic end-caps (EO(132)PO(50)EO(132)). DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) possesses higher affinity with the negatively charged silica and cellulose surfaces while the uncharged copolymer adsorbs to a larger extent on polypropylene surfaces. In this latter case, adsorption increases with increasing solution ionic strength and temperature. Adsorption of EO(132)PO(50)EO(132) on silica surfaces has little effect on the water contact angle (WCA), while adsorption of DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) increases the WCA of silica to 32°, indicating a large density of exposed PPO blocks upon adsorption. After adsorption of EO(132)PO(50)EO(132) and DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) on PP, the WCA is reduced by ≈14° and ≈28°, respectively, due to the exposed hydrophilic EO and highly water-soluble DMAEMA segments on the surfaces. The extent of surface coverage at saturation at the polypropylene/liquid interfaces (≈31 and 40 nm(2)/molecule obtained by QCM and SPR, respectively) is much lower, as expected, when compared with results obtained at the air/liquid interface, where a tighter packing is observed. The percentage of water coupled to the adsorbed cationic polymer decreases with solution ionic strength. Overall, these observations are ascribed to the effects of electrostatic screening, polymer hydrodynamic size, and solvency.}, number={16}, journal={LANGMUIR}, author={Liu, Xiaomeng and Vesterinen, Arja-Helena and Genzer, Jan and Seppala, Jukka V. and Rojas, Orlando J.}, year={2011}, month={Aug}, pages={9769–9780} }
 @misc{galvin_genzer_2012, title={Applications of surface-grafted macromolecules derived from post-polymerization modification reactions}, volume={37}, ISSN={["1873-1619"]}, DOI={10.1016/j.progpolymsci.2011.12.001}, abstractNote={The formation of functional polymers by implementing small-molecule organic chemistry reactions to homopolymers has attracted great attention lately due to an increasing number of novel potential applications. This post-polymerization modification (PPM) approach circumvents a number of problems associated with direct polymer synthesis and enables the creation of polymeric systems that are difficult or impossible to produce otherwise. This holds especially true in the field of polymer brushes where the tethering of the polymer chains to a surface complicates direct polymerization of bulky monomers. The advantages of PPM reactions do not stop with polymer synthesis. This review highlights a variety of innovations that stem directly from this approach. A selection of these applications includes modified barrier properties, catalysis, surface patterning, separations, and biologically active substrates.}, number={7}, journal={PROGRESS IN POLYMER SCIENCE}, author={Galvin, Casey J. and Genzer, Jan}, year={2012}, month={Jul}, pages={871–906} }
 @article{gozen_zhou_roskov_shi_genzer_spontak_2011, title={Block copolymer self-organization vs. interfacial modification in bilayered thin-film laminates}, volume={7}, ISSN={["1744-6848"]}, DOI={10.1039/c0sm01169j}, abstractNote={Block copolymers remain one of the most extensively studied and utilized classes of macromolecules due to their extraordinary abilities to (i) self-assemble spontaneously into a wide variety of soft nanostructures and (ii) reduce the interfacial tension between, and thus compatibilize, immiscible polymer pairs. In bilayered thin-film laminates of immiscible homopolymers, block copolymers are similarly envisaged to stabilize such laminates. Contrary to intuition, we demonstrate that highly asymmetric block copolymers can conversely destabilize a laminate, as discerned from macroscopic dewetting behavior, due to dynamic competition between copolymer self-organization away from and enrichment at the bilayer interface. The mechanism of this counterintuitive destabilization is interrogated through complementary analysis of laminates containing mixtures of stabilizing/destabilizing diblock copolymers and time-dependent Ginzburg–Landau computer simulations. This combination of experiments and simulations reveals a systematic progression of supramolecular-level events that establish the relative importance of molecular aggregation and lateral interfacial structuring in a highly nonequilibrium environment.}, number={7}, journal={SOFT MATTER}, author={Gozen, Arif O. and Zhou, Jiajia and Roskov, Kristen E. and Shi, An-Chang and Genzer, Jan and Spontak, Richard J.}, year={2011}, pages={3268–3272} }
 @article{volden_genzer_zhu_ese_nystrom_glomm_2011, title={Charge- and temperature-dependent interactions between anionic poly (N-isopropylacrylamide) polymers in solution and a cationic surfactant at the water/air interface}, volume={7}, ISSN={["1744-683X"]}, DOI={10.1039/c1sm05671a}, abstractNote={Due to their expanded coil to collapsed globule transition close to physiological temperatures, N-isopropylacrylamide (NIPAAM) polymers and derivatives thereof represent promising drug delivery vectors. Here, we report on the interaction between anionic PNIPAAM derivatives containing potassium 3-sulfopropylmethacrylate (SPMA) blocks of various sizes and a cationic lipid membrane mimic as a function of temperature, polymer charge density and molecular weight, by injection under a pre-compressed surfactant monolayer. The resulting film properties (including equilibria) were studied using surface pressure–area isotherms, Brewster angle microscopy, and interfacial 2D oscillatory rheology. Whereas mixed films of dioctadecyldimethylammonium bromide (DODAB) and an uncharged PNIPAAM homopolymer resulted in distinct polymer and surfactant domains, the anionic polyelectrolytes were found to ionically cross-link and contract the DODAB film. Film penetration, charge screening and surfactant film contraction were dependent on the molecular weight and size of the SPMA blocks on the polymers.}, number={18}, journal={SOFT MATTER}, author={Volden, Sondre and Genzer, Jan and Zhu, Kaizheng and Ese, Marit-Helen G. and Nystrom, Bo and Glomm, Wilhelm R.}, year={2011}, pages={8498–8507} }
 @article{gallow_jhon_tang_genzer_loo_2011, title={Cloud Point Suppression in Dilute Solutions of Model Gradient Copolymers with Prespecified Composition Profiles}, volume={49}, ISSN={["1099-0488"]}, DOI={10.1002/polb.22226}, abstractNote={AbstractGradient copolymers of 2‐hydroxyethyl methacrylate (HEMA) and 2‐(dimethylamino)ethyl methacrylate (DMAEMA) having prescribed linear, parabolic, and hyperbolic composition profiles were synthesized with the guidance of a numerical model that determines the instantaneous comonomer feed rate. These materials exhibit low polydispersity indices (<1.1); the evolution of the overall DMAEMA content and the absolute molecular weight of the copolymers are all in good agreement with the quantities predicted by our model. Compared to random copolymers of HEMA and DMAEMA, the cloud points of dilute buffered aqueous solutions of gradient copolymers decrease with increasing gradient strength; where the gradient strength is defined as the largest difference in the instantaneous composition along the copolymer. The temperature range over which the solutions transition from transparent to turbid also broadens significantly with increasing gradient strength. Both observations suggest the onset of transition to be dictated by the least soluble ends of the polymer chains. These correlations point to the importance of monomer sequence distribution in determining the macroscopic physical properties of copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011}, number={9}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Gallow, Keith C. and Jhon, Young K. and Tang, Wei and Genzer, Jan and Loo, Yueh-Lin}, year={2011}, month={May}, pages={629–637} }
 @article{malik_hall_genzer_2011, title={Effect of copolymer compatibilizer sequence on the dynamics of phase separation of immiscible binary homopolymer blends}, volume={7}, ISSN={["1744-6848"]}, DOI={10.1039/c1sm06292a}, abstractNote={We present the results of kinetic Monte Carlo simulations aimed at exploring the effect of copolymer sequence distribution on the dynamics of phase separation of an immiscible A/B binary homopolymer blend. Diblock, protein-like copolymers (PLCs), simple linear gradient, random, and alternating copolymers having equal number of A and B segments, identical chemical composition, and chain length are considered as compatibilizers. All copolymers, irrespective of their sequence, retard the phase separation process by migrating to the biphasic interface between the A/B interface, thereby minimizing the interfacial energy and promoting adhesion between the homopolymer-rich phases. As expected, diblock copolymers perform the best and each block of the diblock copolymer penetrates the energetically favorable homopolymer-rich phase. Alternating copolymers lie at the interface and PLCs, simple linear gradient, and random copolymers weave back and forth across the interface. The weaving and penetration is more pronounced for PLCs than for simple linear gradient and random copolymers. Judging by the contact analysis, extension and conformation of the copolymers at the interface, and structure factor calculations, it is evident that for the chain lengths considered in our simulations, PLCs are better compatibilizers than alternating and random copolymers, while being on a par with simple linear gradient copolymers, but not as good as diblocks.}, number={22}, journal={SOFT MATTER}, author={Malik, Ravish and Hall, Carol K. and Genzer, Jan}, year={2011}, pages={10620–10630} }
 @article{liu_he_salas_pasquinelli_genzer_rojas_2012, title={Experimental and Computational Study of the Effect of Alcohols on the Solution and Adsorption Properties of a Nonionic Symmetric Triblock Copolymer}, volume={116}, ISSN={1520-6106 1520-5207}, url={http://dx.doi.org/10.1021/jp207190c}, DOI={10.1021/jp207190c}, abstractNote={This study investigates the effect of alcohols on the solution and adsorption properties of symmetric triblock nonionic copolymers comprising blocks of ethylene oxide (EO) and propylene oxide (PO) (EO(37)PO(56)EO(37)). The cloud point, surface tension, critical micelle concentration (CMC), and maximum packing at the air-water interface are determined, and the latter is compared to the amount of polymer that adsorbs from solution onto polypropylene (PP) and cellulose surfaces. The interaction energy and radius of micelles are calculated by using molecular dynamics (MD) simulations. Equivalent MD bead parameters were used in dynamic density functional theory (DDFT) simulations to study the influence of alcohols on the phase behavior of EO(37)PO(56)EO(37) and its adsorption on PP from aqueous solutions. The simulation results agree qualitatively with the experimental observations. Ethanol acts as a good cosolvent for EO(37)PO(56)EO(37) and reduces the amount of EO(37)PO(56)EO(37) that adsorbs on PP surfaces; however, little or no influence is observed on the adsorption on cellulose. Interestingly, longer chain alcohols, such as 1-pentanol, produce the opposite effect. Overall, the solution and adsorption properties of nonionic symmetric triblock copolymers in the presence of alcohols are rationalized by changes in solvency and the hydrophobic effect.}, number={4}, journal={The Journal of Physical Chemistry B}, publisher={American Chemical Society (ACS)}, author={Liu, Xiaomeng and He, Feng and Salas, Carlos and Pasquinelli, Melissa A. and Genzer, Jan and Rojas, Orlando J.}, year={2012}, month={Jan}, pages={1289–1298} }
 @article{jhon_arifuzzaman_özçam_kiserow_genzer_2012, title={Formation of Polyampholyte Brushes via Controlled Radical Polymerization and Their Assembly in Solution}, volume={28}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/la203697a}, DOI={10.1021/la203697a}, abstractNote={We describe the formation of polyampholytic block copolymer brushes and their assembly in solution. Specifically, we employ "surface-initiated" activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) sequentially to form diblock copolymer grafts comprising blocks of poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and poly(sodium methacrylate) (PNaMA) on flat impenetrable silica surfaces, i.e., SiO(x)/PNaMA-b-PDMAEMA and SiO(x)/PDMAEMA-b-PNaMA. Protonation of the PNaMA block results in formation of poly(methacrylic acid) (PMAA). We demonstrate that ARGET-ATRP of NaMA provides a convenient route to preparation of PMAA, which is an alternative method to the more traditional approach based on preparing PMAA by polymerizing tert-butyl methacrylate (tBMA) followed by cleavage of the tert-butyl group. We also discuss conformational changes of the individual polyelectrolyte blocks in solution as a function of solution pH by monitoring adsorption behavior of functionalized polystyrene spheres.}, number={1}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Jhon, Young K. and Arifuzzaman, Shafi and Özçam, Ali E. and Kiserow, Douglas J. and Genzer, Jan}, year={2012}, month={Jan}, pages={872–882} }
 @article{voltrova_hidasova_genzer_srogl_2011, title={Metallothionein-inspired prototype of molecular pincer}, volume={47}, ISSN={["1364-548X"]}, DOI={10.1039/c1cc11463h}, abstractNote={Study of Zn and Pb release from complexes with natural and synthetic amidothiol motifs inspired the design of a "molecular pincer" that scavenges quantitatively metals from liquid environment and releases them, on-demand, under very mild oxidative conditions.}, number={28}, journal={CHEMICAL COMMUNICATIONS}, author={Voltrova, Svatava and Hidasova, Denisa and Genzer, Jan and Srogl, Jiri}, year={2011}, pages={8067–8069} }
 @article{liu_goli_genzer_rojas_2011, title={Multilayers of Weak Polyelectrolytes of Low and High Molecular Mass Assembled on Polypropylene and Self-Assembled Hydrophobic Surfaces}, volume={27}, ISSN={["0743-7463"]}, DOI={10.1021/la200349p}, abstractNote={Hydrophobic self-assembled octadecyltrichlorosilane (ODTS), ultrathin films of polypropylene, and ODTS modified with cationic dioctadecyldimethylammonium bromide are employed as substrates for deposition of multilayers of poly(allylamine hydrochloride) and poly(acrylic acid) from aqueous solution. The assembly of highly dissipative polyelectrolyte multilayers (PEMs) is demonstrated by quartz crystal microgravimetry. The initial rate of adsorption is faster and the adsorbed amount larger on the cationic surface, while the detailed structure of the PEMs, as determined by atomic force microscopy imaging, is related primarily to the molecular weight of the adsorbing polymers. A more extensive PEM adsorption on the hydrophobic surfaces takes place with increasing ionic strength of the background electrolyte solution. The water contact angle depends on the type of polymer adsorbed as the outermost layer, indicating that, despite the expected interdiffusion for the different polymer chains, there is a net macromolecular segregation to the free surface. Surface modification with the high molecular weight PEMs produces a more marked reduction of the hydrophilicity of the substrate.}, number={8}, journal={LANGMUIR}, author={Liu, Xiaomeng and Goli, Kiran K. and Genzer, Jan and Rojas, Orlando J.}, year={2011}, month={Apr}, pages={4541–4550} }
 @article{malik_hall_genzer_2011, title={Phase Separation Dynamics for a Polymer Blend Compatibilized by Protein-like Copolymers: A Monte Carlo Simulation}, volume={44}, ISSN={["0024-9297"]}, DOI={10.1021/ma2014832}, abstractNote={We use Monte Carlo simulation based on the bond fluctuation model to investigate how adding ≈4.92% protein-like copolymer (PLC) to an immiscible binary polymer blend affects the dynamics of phase separation. PLCs slow down effectively the process of phase separation in binary blends by migrating to the biphasic interface between the immiscible homopolymers, thereby reducing the interfacial tension. The ability of PLCs to retard effectively the process of phase separation depends sensitively on the interaction energy between the PLCs and homopolymers and the PLC chain length. PLCs compatibilize the binary blend more effectively with increasing attractive interaction between the PLC blocks and homopolymers. Nominal improvement in compatibilization of the binary blend is achieved with increasing PLC chain length. The growth of phase-separated domains follows a dynamical scaling law for both the binary blend and PLC compatibilized ternary blend in the late stages of phase separation. The universal scaling fun...}, number={20}, journal={MACROMOLECULES}, author={Malik, Ravish and Hall, Carol K. and Genzer, Jan}, year={2011}, month={Oct}, pages={8284–8293} }
 @article{lane_kuang_yom_arifuzzaman_genzer_farmer_naik_vaia_2011, title={Poly(2-hydroxyethyl methacrylate) for Enzyme Immobilization: Impact on Activity and Stability of Horseradish Peroxidase}, volume={12}, ISSN={["1526-4602"]}, DOI={10.1021/bm200173y}, abstractNote={On the basis of their versatile structure and chemistry as well as tunable mechanical properties, polymer brushes are well-suited as supports for enzyme immobilization. However, a robust surface design is hindered by an inadequate understanding of the impact on activity from the coupling motif and enzyme distribution within the brush. Herein, horseradish peroxidase C (HRP C, 44 kDa), chosen as a model enzyme, was immobilized covalently through its lysine residues on a N-hydroxysuccinimidyl carbonate-activated poly(2-hydroxyethyl methacrylate) (PHEMA) brush grafted chemically onto a flat impenetrable surface. Up to a monolayer coverage of HRP C is achieved, where most of the HRP C resides at or near the brush-air interface. Molecular modeling shows that lysines 232 and 241 are the most probable binding sites, leading to an orientation of the immobilized HRP C that does not block the active pocket of the enzyme. Michaelis-Menten kinetics of the immobilized HRP C indicated little change in the K(m) (Michaelis constant) but a large decrease in the V(max) (maximum substrate conversion rate) and a correspondingly large decrease in the k(cat) (overall catalytic rate). This indicates a loss in the percentage of active enzymes. Given the relatively ideal geometry of the HRPC-PHEMA brush, the loss of activity is most likely due to structural changes in the enzyme arising from either secondary constraints imposed by the connectivity of the N-hydroxysuccinimidyl carbonate linking moiety or nonspecific interactions between HRP C and DSC-PHEMA. Therefore, a general enzyme-brush coupling motif must optimize reactive group density to balance binding with neutrality of surroundings.}, number={5}, journal={BIOMACROMOLECULES}, author={Lane, Sarah M. and Kuang, Zhifeng and Yom, Jeannie and Arifuzzaman, Shafi and Genzer, Jan and Farmer, Barry and Naik, Rajesh and Vaia, Richard A.}, year={2011}, month={May}, pages={1822–1830} }
 @article{ahmed_yang_ozcam_efimenko_weiger_genzer_haugh_2011, title={Poly(vinylmethylsiloxane) Elastomer Networks as Functional Materials for Cell Adhesion and Migration Studies}, volume={12}, ISSN={["1526-4602"]}, DOI={10.1021/bm101549y}, abstractNote={Cell migration is central to physiological responses to injury and infection and in the design of biomaterial implants. The ability to tune the properties of adhesive materials and relate those properties in a quantitative way to the dynamics of intracellular processes remains a definite challenge in the manipulation of cell migration. Here, we propose the use of poly(vinylmethylsiloxane) (PVMS) networks as novel substrata for cell adhesion and migration. These materials offer the ability to tune independently chemical functionality and elastic modulus. Importantly, PVMS networks are compatible with total internal reflection fluorescence (TIRF) microscopy, which is ideal for interrogating the cell-substratum interface; this latter characteristic presents a distinct advantage over polyacrylamide gels and other materials that swell with water. To demonstrate these capabilities, adhesive peptides containing the arginyl-glycyl-aspartic acid (RGD) tripeptide motif were successfully grafted to the surface of PVMS network using a carboxyl-terminated thiol as a linker. Peptide-specific adhesion, spreading, and random migration of NIH 3T3 mouse fibroblasts were characterized. These experiments show that a peptide containing the synergy sequence of fibronectin (PHSRN) in addition to RGD promotes more productive cell migration without markedly enhancing cell adhesion strength. Using TIRF microscopy, the dynamics of signal transduction through the phosphoinositide 3-kinase pathway were monitored in cells as they migrated on peptide-grafted PVMS surfaces. This approach offers a promising avenue for studies of directed migration and mechanotransduction at the level of intracellular processes.}, number={4}, journal={BIOMACROMOLECULES}, publisher={American Chemical Society (ACS)}, author={Ahmed, Shoeb and Yang, Hyun-kwan and Ozcam, Ali E. and Efimenko, Kirill and Weiger, Michael C. and Genzer, Jan and Haugh, Jason M.}, year={2011}, month={Apr}, pages={1265–1271} }
 @article{liu_boyles_genzer_dickey_2012, title={Self-folding of polymer sheets using local light absorption}, volume={8}, ISSN={["1744-6848"]}, DOI={10.1039/c1sm06564e}, abstractNote={This paper demonstrates experimentally and models computationally a novel and simple approach for self-folding of thin sheets of polymer using unfocused light. The sheets are made of optically transparent, pre-strained polystyrene (also known as Shrinky-Dinks) that shrink in-plane if heated uniformly. Black ink patterned on either side of the polymer sheet provides localized absorption of light, which heats the underlying polymer to temperatures above its glass transition. At these temperatures, the predefined inked regions (i.e., hinges) relax and shrink, and thereby cause the planar sheet to fold into a three-dimensional object. Self-folding is therefore achieved in a simple manner without the use of multiple fabrication steps and converts a uniform external stimulus (i.e., unfocused light) on an otherwise compositionally homogenous substrate into a hinging response. Modeling captures effectively the experimental folding trends as a function of the hinge width and support temperature and suggests that the hinged region must exceed the glass transition temperature of the sheet for folding to occur.}, number={6}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Liu, Ying and Boyles, Julie K. and Genzer, Jan and Dickey, Michael D.}, year={2012}, pages={1764–1769} }
 @article{turgman-cohen_genzer_2011, title={Simultaneous Bulk- and Surface-Initiated Controlled Radical Polymerization from Planar Substrates}, volume={133}, ISSN={["0002-7863"]}, DOI={10.1021/ja2081636}, abstractNote={We employ Monte Carlo computer simulations to investigate the simultaneous controlled radical polymerization in solution and from a flat surface. The bulk polymers grow at faster rates and possess narrower molecular weight distribution than polymers initiated from flat, impenetrable surfaces. The rate of surface-initiated polymerization depends on the density of initiator sites. Our results provide evidence that the assumption that the molecular weight of surface-initiated polymers is equal to that of polymers grown in bulk, invoked often in determining the grafting density of surface-bound polymers, is generally invalid.}, number={44}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Turgman-Cohen, Salomon and Genzer, Jan}, year={2011}, month={Nov}, pages={17567–17569} }
 @article{genzer_arifuzzaman_bhat_efimenko_ren_szleifer_2012, title={Time Dependence of Lysozyme Adsorption on End-Grafted Polymer Layers of Variable Grafting Density and Length}, volume={28}, ISSN={["0743-7463"]}, DOI={10.1021/la2038747}, abstractNote={A combined experimental and theoretical approach establishes the long-lived nature of protein adsorption on surfaces coated with chemically grafted macromolecules. Specifically, we monitor the time dependence of adsorption of lysozyme on surfaces comprising polymer assemblies made of poly(2-hydroxyethyl methacrylate) brushes grafted onto flat silica surfaces such that they produce patterns featuring orthogonal and gradual variation of the chain length (N) and grafting density (σ). We show that in the kinetically controlled regime, the amount of adsorbed protein scales universally with the product σN, while at equilibrium the amount of adsorbed protein is governed solely by σ. Surprisingly, for moderate concentrations of protein in solution, adsorption takes more than 72 h to reach an equilibrium, or steady state. Our experimental findings are corroborated with predictions using molecular theory that provides further insight into the protein adsorption phenomenon. The theory predicts that the universal behavior observed experimentally should be applicable to polymers in poor and theta solvents and to a limited extent also to good solvent conditions. Our combined experimental and theoretical findings reveal that protein adsorption is a long-lived phenomenon, much longer than generally assumed. Our studies confirm the previously predicted important differences in behavior for the kinetic versus thermodynamic control of protein adsorption.}, number={4}, journal={LANGMUIR}, author={Genzer, Jan and Arifuzzaman, Shafi and Bhat, Rajendra R. and Efimenko, Kirill and Ren, Chun-lai and Szleifer, Igal}, year={2012}, month={Jan}, pages={2122–2130} }
 @article{liu_wu_turgman-cohen_genzer_theyson_rojas_2010, title={Adsorption of a Nonionic Symmetric Triblock Copolymer on Surfaces with Different Hydrophobicity}, volume={26}, ISSN={["0743-7463"]}, DOI={10.1021/la100156a}, abstractNote={This study investigates the adsorption of a symmetric triblock nonionic polymer comprising ethylene oxide (EO) and propylene oxide (PO) blocks (Pluronic P-105, EO(37)PO(56)EO(37)) on a range of substrates including hydrophobic, i.e., polypropylene (PP), poly(ethylene terephthalate) (PET), nylon, and graphite, and hydrophilic, i.e., cellulose and silica. The adsorption process and the structure of the hydrated adsorbed layers are followed by quartz crystal microgravimetry (QCM), surface plasmon resonance (SPR), and atomic force microscopy. The unhydrated surfaces are characterized by ellipsometry and contact angle techniques. The adsorption kinetics and the extent of adsorption are determined by monitoring the changes in resonance frequency and refractive index of sensors coated with ultrathin films of the various substrates. Langmuirian-type adsorption kinetics is observed in all cases studied. The amount of adsorbed Pluronic on hydrophobic polymer surfaces (PP, PET, and nylon) exceeds that on the hydrophilic cellulose. The hydrophobic (graphite) mineral surface adsorbs relatively low polymer mass, typical of a monolayer, while micellar structures are observed on the hydrophilic silica surface. The amount of water coupled to the adsorbed polymer layers is quantified by combining data from QCM, and SPR are found to increase with increasing polarity of the substrate. On the basis of contact angle data, the nonhydrated adsorbed structures produce modest increases in hydrophilicity of all the substrates investigated. Overall, insights are provided into the structure and stability of both hydrated and nonhydrated adsorbed triblock copolymer.}, number={12}, journal={LANGMUIR}, author={Liu, Xiaomeng and Wu, Dong and Turgman-Cohen, Salomon and Genzer, Jan and Theyson, Thomas W. and Rojas, Orlando J.}, year={2010}, month={Jun}, pages={9565–9574} }
 @article{turgman-cohen_genzer_2010, title={Computer Simulation of Controlled Radical Polymerization Effect of Chain Confinement Due to Initiator Grafting Density and Solvent Quality in "Grafting From" Method}, volume={43}, ISSN={["1520-5835"]}, DOI={10.1021/ma102046q}, abstractNote={We use stochastic Monte Carlo simulation following the bond fluctuation model to study the effects of grafting density of surface-anchored initiators and solvent quality on controlled radical polymerization (CRP) from flat impenetrable substrates under good and poor solvent conditions. Our CRP model includes a mechanism for activation/deactivation of the chains and neglects termination and chain transfer reactions. The system is, thus, “truly living”. We find that under these conditions, surface-initiated polymerizations at low grafting densities resemble those in the bulk. In contrast, at high initiator grafting densities, these surface-initiated polymerizations result in gradients of the free monomer and chain-end concentrations, which lead to an uneven growth of the chains and ultimately yield polymers with broad molecular weight distributions. Poor solvent conditions exacerbate this problem by collapsing the chains and in some cases forming chain aggregates, which further restrict the access of free m...}, number={22}, journal={MACROMOLECULES}, author={Turgman-Cohen, Salomon and Genzer, Jan}, year={2010}, month={Nov}, pages={9567–9577} }
 @article{strickland_hall_genzer_2010, title={Controlling comonomer distribution in random copolymers by chemical coloring of surface-tethered homopolymers: An insight from discontinuous molecular dynamics simulation}, volume={26}, DOI={10.1021/la9045513}, abstractNote={Postpolymerization chemical modification ("coloring") of homopolymer brushes made of A units using B chemical moieties produces surface-anchored random copolymers (RCPs) A(1-x)B(x), where x is the degree of "coloring". We employ discontinuous molecular dynamics to study the "coloring" process in macromolecular tethers made of various lengths grafted at low and high densities on flat impenetrable surfaces. We demonstrate that the comonomer distribution in the A(1-x)B(x) RCPs depends on the interplay among (1) the length and the grafting density of the A-based homopolymer anchors, (2) the solubility of the parent homopolymer, and (3) the solubility of the B coloring units. Chemical modification of sparsely spaced chains on the surface leads to nearly random comonomer distribution in the A(1-x)B(x) RCPs regardless of the solubility of A and B. In contrast, the distribution of A and B units in A(1-x)B(x) RCPs prepared from homopolymers tethered at high grafting densities depends on the solubility of the parent homopolymer. Chemical modification of well-solvated A homopolymer grafts results in comonomer distributions that resemble those of diblock copolymers, comprising lightly modified blocks near the surface and heavily "colored" blocks at the top of the grafts. The relative lengths of the two blocks can be tuned by varying the solubility of B. Under poor solvent conditions, the distribution of A and B in the A(1-x)B(x) RCP is more complex; it is governed by the conformation of the parent A macromolecular anchors that form collapsed clusters before the coloring reaction.}, number={11}, journal={Langmuir}, author={Strickland, L. A. and Hall, C. K. and Genzer, Jan}, year={2010}, pages={8810–8820} }
 @misc{stuart_huck_genzer_mueller_ober_stamm_sukhorukov_szleifer_tsukruk_urban_et al._2010, title={Emerging applications of stimuli-responsive polymer materials}, volume={9}, ISSN={["1476-4660"]}, DOI={10.1038/nmat2614}, abstractNote={Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.}, number={2}, journal={NATURE MATERIALS}, author={Stuart, Martien A. Cohen and Huck, Wilhelm T. S. and Genzer, Jan and Mueller, Marcus and Ober, Christopher and Stamm, Manfred and Sukhorukov, Gleb B. and Szleifer, Igal and Tsukruk, Vladimir V. and Urban, Marek and et al.}, year={2010}, month={Feb}, pages={101–113} }
 @article{tonelli_jhon_genzer_2010, title={Glass Transition Temperatures of Styrene/4-BrStyrene Copolymers with Variable Co-Monomer Compositions and Sequence Distributions}, volume={43}, ISSN={["0024-9297"]}, DOI={10.1021/ma101355f}, abstractNote={In both equations WA and WB are the weight fractions of comonomer units A and B. In eq 1 TgA and TgB are the glass transition temperatures of homopolymers poly-A and poly-B, and in eq 2 PAA, PAB =PBA, PBB and TgAA, TgAB, TgBB are the probabilities/populations of and glass-transitions temperatures contributed by each distinct comonomer diad. Figure 1 illustrates both behaviors, as observed in methacrylate (MA) copolymers with vinyl chloride (VC) and vinylidene chloride (VDC). While VC-MA copolymers follow the weightadditive relation (eq 1) of Fox et al., VDC-MA copolymers deviate strongly, with observed Tgps far above those given by the Fox equation, even though the Tgs of PMA and PVDC homopolymers are nearly identical. This is particularly evident when comparing the Tgps of random and regularly alternating VDCMA copolymers, each having the same overall 50:50 molar composition. The 50:50 random VDC-MA copolymer has a Tgp some 35 C above that predicted by the Fox relation (eq 1), while the regularly alternating sample’sTgp is an additional 15 C higher than that of the 50:50 random copolymer. The contrasting Tgp behavior evidenced byVC-MAandVDC-MAcopolymers was previously suggested to be the consequence of the conformational flexibilities of their individual copolymer chains. Therewe put forward the following relationship to describe the deviation between the glass-transition temperatures observed for copolymers Tgp(obs) and those predicted by the Fox Relation (eq 1), Tgp(Fox), dependent solely upon the overall weight-average chemical composition of comonomers:}, number={16}, journal={MACROMOLECULES}, author={Tonelli, Alan E. and Jhon, Young K. and Genzer, Jan}, year={2010}, month={Aug}, pages={6912–6914} }
 @article{crowe-willoughby_stevens_genzer_clarke_2010, title={Investigating the Molecular Origins of Responsiveness in Functional Silicone Elastomer Networks}, volume={43}, ISSN={["1520-5835"]}, DOI={10.1021/ma100470w}, abstractNote={Dielectric, calorimetric, and dynamic mechanical measurements were performed to delineate the types and dynamic rates of molecular scale motion in modified poly(vinylmethyl siloxane) (PVMS) stimuli-responsive networks, where pendent groups of the form -S-(CH2)n-OH were chemically attached to the vinyl moiety of PVMS. The glass transition temperature (Tg) for the unsubstituted PVMS network matches that previously reported for linear PVMS indicating that the flexibility of the polymer chains is unaffected by the network cross-linking. In contrast, Tg increases with the introduction of pendent groups of the type -S-(CH2)n-CH3 or -S-(CH2)n-OH, where n is 2, 6, or 11, as the different groups constrain the siloxane backbone to differing degrees. The macroscopic response time and amplitude, as previously measured bydynamic contactangle,arecorrelated withtheobservedglass transition temperatures. Onecon- clusion is that the flexibility of the network and the interactions between pendent groups affect responsiveness.}, number={11}, journal={MACROMOLECULES}, author={Crowe-Willoughby, Julie A. and Stevens, Derrick R. and Genzer, Jan and Clarke, Laura I.}, year={2010}, month={Jun}, pages={5043–5051} }
 @article{smith_mcgillivray_genzer_losche_kilpatrick_2010, title={Neutron reflectometry of supported hybrid bilayers with inserted peptide}, volume={6}, ISSN={["1744-683X"]}, DOI={10.1039/b915800f}, abstractNote={The insertion of a synthetic amphiphilic, α-helical peptide into a supported hybrid bilayer membrane (HBM) was studied by neutron reflectometry to elucidate the resulting nanostructure. The HBM consisted of a self-assembled monolayer of perdeuterated octadecanethiol on gold and an overlying leaflet of acyl-deuterated phosphatidylcholine (d-DMPC). Using contrast variation, several reflectivity spectra were recorded for each step of film fabrication, and simultaneously modeled. This analysis indicated that peptide insertion into the DMPC lipid leaflet is the likeliest mode of incorporation.}, number={5}, journal={SOFT MATTER}, author={Smith, Matthew B. and McGillivray, Duncan J. and Genzer, Jan and Losche, Mathias and Kilpatrick, Peter K.}, year={2010}, pages={862–865} }
 @article{yang_ozcam_efimenko_genzer_2011, title={Photochromic materials with tunable color and mechanical flexibility}, volume={7}, ISSN={["1744-683X"]}, DOI={10.1039/c0sm00928h}, abstractNote={Florescence switches based on photochromic compounds have been fabricated previously and identified as potential candidates for information technology. Recently, optically responsive materials with tunable color have been prepared by dissolving photochromic compounds, such as spiropyran (SP), into solutions of various pH or embedding them into sol–gel matrices with adjusted chemical compositions. Here we report on fabricating flexible rubbers with tunable color by embedding SP molecules inside silicone elastomer networks (SENs) based on poly(vinylmethylsiloxane) (PVMS). SP-containing PVMS networks have been further modified either physically by exposing them to ultraviolet/ozone treatment or chemically by attaching functional thiols to the vinyl bonds in PVMS via UV-activated thiol–ene addition. The color hue of the SP–PVMS SENs after exposing to UV light depends on either the UVO dose or the chemical end-functionality of the thiol modifier, respectively. We also present simple methodologies enabling patterning regions in SP-doped SENs with various shapes and colors.}, number={8}, journal={SOFT MATTER}, author={Yang, Hyun-Kwan and Ozcam, A. Evren and Efimenko, Kirill and Genzer, Jan}, year={2011}, pages={3766–3774} }
 @article{cho_lee_jhon_genzer_char_2010, title={Polymer Nanotubules Obtained by Layer-by-Layer Deposition within AAO-Membrane Templates with Sub-100-nm Pore Diameters}, volume={6}, ISSN={["1613-6829"]}, DOI={10.1002/smll.201001212}, abstractNote={The preparation and features of nanotubes consisting of various materials have attracted signifi cant attention over the past few years because of their potential applications in microelectronics, biosensors, drug-delivery systems, and many other fi elds. The layer-by-layer (LbL) deposition technique on templates has been one of the most popular methods for the formation of nanotubes. Any size and shape of template can be utilized and the desired amount of various materials including polyelectrolytes, [ 1,2 ] biomolecules, [ 3,4 ]}, number={23}, journal={SMALL}, author={Cho, Younghyun and Lee, Woo and Jhon, Young Kuk and Genzer, Jan and Char, Kookheon}, year={2010}, month={Dec}, pages={2683–2689} }
 @article{malik_hall_genzer_2010, title={Protein-Like Copolymers (PLCs) as Compatibilizers for Homopolymer Blends}, volume={43}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ma100460y}, DOI={10.1021/ma100460y}, abstractNote={We present the results of discontinuous molecular dynamics (DMD) computer simulations aimed at understanding the role of protein-like copolymers (PLCs) as compatibilizing agents for a polymer blend...}, number={11}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Malik, Ravish and Hall, Carol K. and Genzer, Jan}, year={2010}, month={Jun}, pages={5149–5157} }
 @article{strickland_hall_genzer_2010, title={Simulation of Mechanically-Assembled Monolayers In Poor Solvent Using Discontinuous Molecular Dynamics}, volume={43}, ISSN={["0024-9297"]}, DOI={10.1021/ma9026417}, abstractNote={We present and discuss the results of discontinuous molecular dynamics simulations of mechanically assembled polymer layers chemically attached to flexible substrates under poor solvent conditions. Square-well chains of lengths comprising 20 to 100 units end-grafted to a hard surface at low density are compressed laterally at varying rates. Brush thickness depends on the interplay between solvent quality and the substrate compression rate. Brushes formed in poor solvents at fast compression rates are thinner and exhibit more heterogeneity in coverage than brushes formed in good solvents at slow compression rates. End-monomer trapping increases with increasing compression rate and/or decreasing solvent quality. By varying relaxation/compression rate, we can modify the effects of brush thickness hysteresis. Finally, we suggest a general blueprint for efficient formation of defect-free monolayers that might be followed by experimenters.}, number={6}, journal={MACROMOLECULES}, author={Strickland, L. Anderson and Hall, Carol K. and Genzer, Jan}, year={2010}, month={Mar}, pages={3072–3080} }
 @article{liu_song_wu_genzer_theyson_rojas_2010, title={Surface and Friction Behavior of a Silicone Surfactant Adsorbed on Model Textiles Substrates}, volume={49}, ISSN={["0888-5885"]}, DOI={10.1021/ie1012213}, abstractNote={This study reports on interactions of an amphiphilic block copolymer of polyalkylene oxide-modified poly(dimethylsiloxane) with thin films of polypropylene (PP), polyethylene terephthalate (PET), and nylon, as well as with reference hydrophilic silica surfaces. The dynamics of adsorption, adsorbed mass, and viscoelasticity of the adsorbed layer are quantified by using a quartz crystal microbalance, while boundary layer lubrication behaviors are studied by using lateral force microscopy. Driven by hydrophobic interactions, the silicone surfactant adsorbs following a Langmuir isotherm and forms strongly adsorbed layers on the polymer surfaces with an areal mass directly related to the hydrophobicity of the substrate. The self-assembled silicone surfactant molecules improve significantly wettability and lower friction. The results reported herein will broaden our understanding of lubrication phenomena in textile and fiber processing applications.}, number={18}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Liu, Xiaomeng and Song, Junlong and Wu, Dong and Genzer, Jan and Theyson, Thomas and Rojas, Orlando J.}, year={2010}, month={Sep}, pages={8550–8557} }
 @article{volden_kjoniksen_zhu_genzer_nystrom_glomm_2010, title={Temperature-Dependent Optical Properties of Gold Nanoparticles Coated with a Charged Diblock Copolymer and an Uncharged Triblock Copolymer}, volume={4}, ISSN={["1936-086X"]}, DOI={10.1021/nn901517u}, abstractNote={We demonstrate that the optical properties of gold nanoparticles can be used to detect and follow stimuli-induced changes in adsorbed macromolecules. Specifically, we investigate thermal response of anionic diblock and uncharged triblock copolymers based on poly(N-isopropylacrylamide) (PNIPAAM) blocks adsorbed onto gold nanoparticles and planar gold surfaces in a temperature range between 25 and 60 degrees C. By employing a palette of analytical probes, including UV-visible spectroscopy, dynamic light scattering, fluorescence, and quartz crystal microbalance with dissipation monitoring, we establish that while the anionic copolymer forms monolayers at both low and high temperature, the neutral copolymer adsorbs as a monolayer at low temperatures and forms multilayers above the cloud point (T(C)). Raising the temperature above T(C) severely affects the optical properties of the gold particle/polymer composites, expelling associated water and altering the immediate surroundings of the gold nanoparticles. This effect, stronger for the uncharged polymer, is related to the amount of polymer adsorbed on the surface, where a denser shell influences the surface plasmon band to a greater degree. This is corroborated with light scattering experiments, which reveal that flocculation of the neutral polymer-coated particles occurs at high temperatures. The flocculation behavior of the neutral copolymer on planar gold surfaces results in multilayer formation. The observed effects are discussed within the framework of the Mie-Drude theory.}, number={2}, journal={ACS NANO}, author={Volden, Sondre and Kjoniksen, Anna-Lena and Zhu, Kaizheng and Genzer, Jan and Nystrom, Bo and Glomm, Wilhelm R.}, year={2010}, month={Feb}, pages={1187–1201} }
 @article{cadova_konecny_kriz_svitakova_holler_genzer_vlcek_2010, title={ATRP of 2-Vinylpyridine and tert-Butyl Acrylate Mixtures Giving Precursors of Polyampholytes}, volume={48}, ISSN={["1099-0518"]}, DOI={10.1002/pola.23805}, abstractNote={INTRODUCTION Polymers bearing ionic groups represent an important class of macromolecules; they can either be of natural origin (i.e., peptides) or synthetic (polymer emulsifiers). Ion-containing polymers can be divided into two major groups; (i) polyelectrolytes that possess either anionic or cationic groups and (ii) polyzwitterions (polyampholytes), which carry both the anionic and cationic moieties. The charges in zwitterionic polymers can be either located on the side chains of different monomer units or the same unit. For instance, in polybetaines both charge types can be dispersed along the polymer backbone. In addition to polymer/ solvent interactions, the properties and structure of polyampholytes are governed by the Coulombic interactions acting among positively and negatively charged sites present in the polymer and the counterions surrounding the macromolecule in solution. Both the structure of the charged groups and the polymer composition also play an important role in determining the behavior of such macromolecular moieties.}, number={3}, journal={JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY}, author={Cadova, Eva and Konecny, Jiri and Kriz, Jaroslav and Svitakova, Romana and Holler, Petr and Genzer, Jan and Vlcek, Petr}, year={2010}, month={Feb}, pages={735–741} }
 @article{turgman-cohen_fischer_kilpatrick_genzer_2009, title={Asphaltene Adsorption onto Self-Assembled Monolayers of Alkyltrichlorosilanes of Varying Chain Length}, volume={1}, ISSN={["1944-8244"]}, DOI={10.1021/am900203u}, abstractNote={The adsorption of asphaltenes onto flat silica surfaces modified with self-assembled monolayers (SAMs) of alkyltrichlorosilanes of varying thickness due to a variable number of carbon atoms (N(C)) has been studied by means of contact angle measurements, spectroscopic ellipsometry, and near-edge X-ray absorption fine structure spectroscopy. The extent of asphaltene adsorption was found to depend primarily on the ability of the SAM layer to shield the underlying silicon substrate from interacting with the asphaltenes present in solution. Specifically, asphaltene adsorption decreased with an increase in N(C) and/or an increase in SAM grafting density, sigma(SAM), (i.e., number of SAM molecules per unit area). The effect of the solvent quality on the extent of asphaltene adsorption was gauged by adsorbing asphaltenes from toluene, 1-methylnaphthalene, tetralin, decalin, and toluene-heptanes mixtures. The extent of asphaltene adsorption was found to increase proportionally with a decrease in the Hildebrand solubility parameter of the solvent.}, number={6}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Turgman-Cohen, Salomon and Fischer, Daniel A. and Kilpatrick, Peter K. and Genzer, Jan}, year={2009}, month={Jun}, pages={1347–1357} }
 @article{turgman-cohen_smith_fischer_kilpatrick_genzer_2009, title={Asphaltene Adsorption onto Self-Assembled Monolayers of Mixed Aromatic and Aliphatic Trichlorosilanes}, volume={25}, ISSN={["0743-7463"]}, DOI={10.1021/la9000895}, abstractNote={The adsorption of asphaltenes onto flat solid surfaces modified with mixed self-assembled monolayers (SAMs) of aliphatic and aromatic trichlorosilanes with varying wettabilities, aromaticities, and thicknesses is tested. The mixed SAMs are characterized by means of contact angle to assess hydrophobicity and molecular and chemical uniformity, spectroscopic ellipsometry to measure the thickness of the films, and near edge X-ray absorption fine structure (NEXAFS) spectroscopy to assess chemical and molecular composition. The molecular characteristics of the adsorbed asphaltene layer and the extent of asphaltene adsorption are determined using NEXAFS and spectroscopic ellipsometry, respectively. The SAMs are formed by depositing phenyl-, phenethyl-, butyl-, and octadecyl- trichlorosilanes from toluene solutions onto silica-coated substrates; the chemical composition and the wettability of the SAM surface is tuned systematically by varying the trichlorosilane composition in the deposition solutions. The adsorption of asphaltenes on the substrates does not correlate strongly with the SAM chemical composition. Instead, the extent of asphaltene adsorption decreases with increasing SAM thickness. This observation suggests that the leading interaction governing the adsorption of asphaltenes is their interaction with the polar silica substrate and that the chemical composition of the SAM is of secondary importance.}, number={11}, journal={LANGMUIR}, author={Turgman-Cohen, Salomon and Smith, Matthew B. and Fischer, Daniel A. and Kilpatrick, Peter K. and Genzer, Jan}, year={2009}, month={Jun}, pages={6260–6269} }
 @article{strickland_hall_genzer_2009, title={Design of copolymers with tunable randomness using discontinuous molecular dynamics simulation}, volume={42}, DOI={10.1021/ma901605v}, abstractNote={We present the results of discontinuous molecular dynamics simulations of a “coloring” reaction performed on A-type homopolymers having length ranging from 100 to 300 units in implicit solvents. Th...}, number={22}, journal={Macromolecules}, author={Strickland, L. A. and Hall, C. K. and Genzer, Jan}, year={2009}, pages={9063–9071} }
 @article{sohn_dimitriou_genzer_fischer_hawker_kramer_2009, title={Determination of the Electron Escape Depth for NEXAFS Spectroscopy}, volume={25}, ISSN={["0743-7463"]}, DOI={10.1021/la803951y}, abstractNote={A novel method was developed to determine carbon atom density as a function of depth by analyzing the postedge signal in near-edge X-ray absorption fine structure (NEXAFS) spectra. We show that the common assumption in the analysis of NEXAFS data from polymer films, namely, that the carbon atom density is constant as a function of depth, is not valid. This analysis method is then used to calculate the electron escape depth (EED) for NEXAFS in a model bilayer system that contains a perfluorinated polyether (PFPE) on top of a highly oriented pyrolitic graphite (HOPG) sample. Because the carbon atom densitites of both layers are known, in addition to the PFPE surface layer thickness, the EED is determined to be 1.95 nm. This EED is then used to measure the thickness of the perfluorinated surface layer of poly(4-(1H,1H,2H,2H-perfluorodecyl)oxymethylstyrene) (PFPS).}, number={11}, journal={LANGMUIR}, author={Sohn, K. E. and Dimitriou, M. D. and Genzer, J. and Fischer, D. A. and Hawker, C. J. and Kramer, E. J.}, year={2009}, month={Jun}, pages={6341–6348} }
 @article{efimenko_finlay_callow_callow_genzer_2009, title={Development and Testing of Hierarchically Wrinkled Coatings for Marine Antifouling}, volume={1}, ISSN={["1944-8252"]}, DOI={10.1021/am9000562}, abstractNote={We report on the formation and testing of novel marine coatings comprising hierarchically wrinkled surface topographies (HWTS) having wrinkles of different length scales (generations) ranging from tens of nanometers to a fraction of a millimeter. The individual wrinkle generations are arranged in nested patterns, where each larger wrinkle resides underneath and represents a scaled-up version of the smaller wrinkle. We present and discuss results from field tests in seawater and laboratory experiments. The results of our field tests reveal that while coatings with flat topographies foul after relatively short time periods (4-15 weeks), the HWST coatings with the same chemistries as flat coatings remain relatively free of biofouling even after prolonged exposure to seawater (18 months). In contrast to flat coatings, the HWST substrates are not colonized by barnacles. These observations suggest that surface topography plays a dominant role in governing the coating defense against barnacle fouling even without fine-tuning the chemical composition of the overcoat. Laboratory experiments indicate that settlement of zoospores of the green alga Ulva and the strength of attachment of sporelings (young plants) depend on the chemical composition of the coating as well as surface topography.}, number={5}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Efimenko, Kirill and Finlay, John and Callow, Maureen E. and Callow, James A. and Genzer, Jan}, year={2009}, month={May}, pages={1031–1040} }
 @article{han_jeon_ryu_semler_jhon_genzer_2009, title={Discriminating Among Co-monomer Sequence Distributions in Random Copolymers Using Interaction Chromatography}, volume={30}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200900282}, abstractNote={AbstractInteraction chromatography has been employed to validate that adsorption of poly[styrene‐co‐(4‐bromostyrene)] (PBrxS) random copolymers, where x denotes the mole fraction of 4‐bromostyrene (4–BrS) in PBrxS in solution depends on the average number of adsorptive segments, the type of adsorbing substrate, and on the co‐monomer sequence distribution in PBrxS.magnified image
}, number={18}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Han, Junwon and Jeon, Byung Ho and Ryu, Chang Y. and Semler, James J. and Jhon, Young K. and Genzer, Jan}, year={2009}, month={Sep}, pages={1543–1548} }
 @article{kim_montero_habibi_hinestroza_genzer_argyropoulos_rojas_2009, title={Dispersion of Cellulose Crystallites by Nonionic Surfactants in a Hydrophobic Polymer Matrix}, volume={49}, ISSN={["1548-2634"]}, DOI={10.1002/pen.21417}, abstractNote={AbstractCellulose nanoparticles obtained by acid hydrolysis of cellulose paper were used to reinforce polystyrene composite films. The nonionic surfactant sorbitan monostearate was utilized to improve the dispersion properties of the hydrophilic cellulose in hydrophobic matrix and to prevent the formation of aggregates. Turbidity tests were used to measure dispersion stability of the cellulose crystallites in the hydrophobic solvent used in the composite manufacture. A correlation was found between the dispersion stability in solvent and the formation of aggregates in the polymeric composites. Nanocomposite films were processed using a casting/evaporation technique. Thermal and mechanical properties of processed composites were studied by differential scanning calorimetry (DSC) and dynamical mechanical analyses (DMA), respectively. The results showed that the optimum addition of surfactant produced better dispersion of the cellulose particles in the polystyrene matrix and improved the mechanical properties of the resulting composite due to an enhanced compatibility. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers}, number={10}, journal={POLYMER ENGINEERING AND SCIENCE}, author={Kim, Jooyoun and Montero, Gerardo and Habibi, Youssef and Hinestroza, Juan P. and Genzer, Jan and Argyropoulos, Dimitris S. and Rojas, Orlando J.}, year={2009}, month={Oct}, pages={2054–2061} }
 @article{jhon_semler_genzer_beevers_gus'kova_khalatur_khokhlov_2009, title={Effect of Comonomer Sequence Distribution on the Adsorption of Random Copolymers onto Impenetrable Flat Surfaces}, volume={42}, ISSN={["1520-5835"]}, DOI={10.1021/ma8027936}, abstractNote={We study the effect of comonomer sequence distributions in random copolymers (RCPs) on RCP adsorption on flat impenetrable surfaces. RCP poly(styrene-co-4-bromostyrene) (PBrxS), where x denotes the mole fraction of 4-bromostryrene (4-BrS), is prepared by bromination of parent homopolystyrene. By varying the solvent quality during the bromination, either “truly random” (good solvent) or “random-blocky” (poor solvent) PBrxS RCPs are prepared. Adsorption studies of PBrxS from various solvents at silica surfaces reveal that the adsorption of PBrxS increases with (1) increasing blockiness of the macromolecule, (2) increasing content of 4-BrS in PBrxS, and (3) decreasing solvent quality. Additionally, the effect of comonomer sequence distribution on RCP adsorption is modeled in detail using a coarse-grained statistical mechanical model and fully atomistic simulations based on configurational-biased grand-canonical Monte Carlo (CB-GCMC) technique. The main result from the simulations can be summarized as follows...}, number={7}, journal={MACROMOLECULES}, author={Jhon, Young K. and Semler, James J. and Genzer, Jan and Beevers, Martin and Gus'kova, Olga A. and Khalatur, Pavel G. and Khokhlov, Alexei R.}, year={2009}, month={Apr}, pages={2843–2853} }
 @article{crowe-willoughby_weiger_ozcam_genzer_2010, title={Formation of silicone elastomer networks films with gradients in modulus}, volume={51}, ISSN={["0032-3861"]}, DOI={10.1016/j.polymer.2009.11.070}, abstractNote={We describe the formation of soft material substrates with position-dependent modulus. Two strategies have been employed in the preparation of such materials. In the first method, we create modulus gradient structures by inter-diffusing two (or more) formulations of silicone elastomers (SE), comprising mixtures of poly(dimethylsiloxane) (PDMS) and poly(vinylmethylsiloxane) (PVMS) with varying molecular weight and content of PDMS, and cross-link them thermally in order to form SE networks. With this method, the resultant substrates exhibit shallow modulus gradients that extend over a few centimeters in length. The second technique is based on employing ultraviolet (UV)-based cross-linking of mercapto-terminated PVMS chains across transparency lithographic masks. We demonstrate that the shape and “sharpness” of the modulus on the substrate depends solely on the position-dependent transparency of the mask to the UV light. As a part of the study we provide detailed material characterization of networks formed by the PDMS–PVMS and PVMS-SH chains.}, number={3}, journal={POLYMER}, author={Crowe-Willoughby, Julie A. and Weiger, Katherine L. and Ozcam, Ali E. and Genzer, Jan}, year={2010}, month={Feb}, pages={763–773} }
 @article{arifuzzaman_oezcam_efimenko_fischer_genzer_2009, title={Formation of surface-grafted polymeric amphiphilic coatings comprising ethylene glycol and fluorinated groups and their response to protein adsorption}, volume={4}, ISSN={["1559-4106"]}, DOI={10.1116/1.3114502}, abstractNote={Amphiphilic polymer coatings were prepared by first generating surface-anchored polymer layers of poly(2-hydroxyethyl methacrylate) (PHEMA) on top of flat solid substrates followed by postpolymerization reaction on the hydroxyl terminus of HEMA’s pendent group using three classes of fluorinating agents, including organosilanes, acylchlorides, and trifluoroacetic anhydride (TFAA). The distribution of the fluorinated groups inside the polymer brushes was assessed by means of a suite of analytical probes, including contact angle, ellipsometry, infrared spectroscopy, atomic force microscopy, and near-edge x-ray absorption fine structure spectroscopy. While organosilane modifiers were found to reside primarily close to the tip of the brush, acylchlorides penetrated deep inside PHEMA thus forming random copolymers P(HEMA-co-fHEMA). The reaction of TFAA with the PHEMA brush led to the formation of amphiphilic diblocks, PHEMA-b-P(HEMA-co-fHEMA), whose bottom block comprised unmodified PHEMA and the top block was made of P(HEMA-co-fHEMA) rich in the fluorinated segments. This distribution of the fluorinated groups endowed PHEMA-b-P(HEMA-co-fHEMA) with responsive properties; while in hydrophobic environment P(HEMA-co-fHEMA) segregated to the surface, when in contact with a hydrophilic medium, PHEMA partitioned at the brush surface. The surface activity of the amphiphilic coatings was tested by studying the adsorption of fibrinogen (FIB). While some FIB adsorption occurred on most coatings, the ones made by TFAA modification of PHEMA remained relatively free of FIB.}, number={2}, journal={BIOINTERPHASES}, author={Arifuzzaman, Shafi and Oezcam, Ali E. and Efimenko, Kirill and Fischer, Daniel A. and Genzer, Jan}, year={2009}, month={Jun}, pages={FA33–FA44} }
 @article{han_jeon_ryu_semler_jhon_genzer_2009, title={Macromol. Rapid Commun. 18/2009}, volume={30}, ISSN={1022-1336 1521-3927}, url={http://dx.doi.org/10.1002/marc.200990044}, DOI={10.1002/marc.200990044}, abstractNote={Front Cover: The image shows a schematic illustrating the adsorption- and solvency-mediated detection of chemical composition and co-monomer sequence distribution in random copolymers by means of interaction chromatography (THF: tetrahydrofuran; IO: isooctane; MC: methylene chloride; ACN: acetonitrile). Further details can be found in the article by J. Han, B. H. Jeon, C. Y. Ryu,* J. J. Semler, Y. K. Jhon, and J. Genzer* on page 1543.}, number={18}, journal={Macromolecular Rapid Communications}, publisher={Wiley}, author={Han, Junwon and Jeon, Byung Ho and Ryu, Chang Y. and Semler, James J. and Jhon, Young K. and Genzer, Jan}, year={2009}, month={Sep}, pages={NA-NA} }
 @article{ozcam_efimenko_jaye_spontak_fischer_genzer_2009, title={Modification of PET surfaces with self-assembled monolayers of organosilane precursors}, volume={172}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2009.03.012}, abstractNote={Abstract We report on a facile, robust and rapid method by which poly(ethylene terephthalate) (PET) surfaces can be chemically modified while avoiding chemical degradation. Specifically, we demonstrate that brief exposure of PET surfaces to ultraviolet/ozone (UVO) generates a large surface concentration of hydrophilic moieties that serve as points of chemical attachment, thereby facilitating subsequent chemisorption of organosilane precursors. The feasibility of this methodology is tested by decorating UVO-modified PET surfaces with semifluorinated organosilane (SFOS) molecules, which serve to alter the surface energy of PET without compromising its bulk characteristics. The physico-chemical properties of the SFOS layers attached to PET are studied with a palette of experimental probes, including near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle, atomic force microscopy (AFM), and ellipsometry. Experimental results indicate that ≈2 min of UVO treatment is optimal for covering PET with dense self-assembled monolayers (SAMs) of SFOS. Longer UVO treatment times contaminate and correspondingly roughen PET surfaces with low-molecular-weight organic compounds (LMWOCs) generated from degradation of the topmost PET material. As a consequence, SFOS SAMs attached to the LMWOC layer readily wash off from UVO-treated PET.}, number={1-3}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Ozcam, Ali E. and Efimenko, Kirill and Jaye, Cherno and Spontak, Richard J. and Fischer, Daniel A. and Genzer, Jan}, year={2009}, month={May}, pages={95–103} }
 @article{park_efimenko_sjoblom_genzer_2009, title={Rapid Removal of Organics and Oil Spills from Waters Using Silicone Rubber "Sponges"}, volume={30}, ISSN={["1532-2351"]}, DOI={10.1080/01932690802540384}, abstractNote={We have developed a simple, robust, and efficient technology utilizing cheap and recoverable materials based on commercially available silicone elastomer networks for removing organic solvents and crude oil from waters. Hydrophobic and oleophilic properties of silicone elastomers endow poly(dimethyl siloxane) (PDMS) with the capacity to absorb a large variety of organics, including benzene (B), toluene (T), ethylbenzene (E), and xylene (X), commonly referred to as BTEX, and also crude oils, while at the same time enabling the organic “sponges” to float on waters, which facilitates straightforward handling. We developed a method for generating PDMS particles with variable sizes (ranging from hundreds nanometers to few millimeters) by drop-wise depositing siloxane/cross-linker mixtures into warm water, a process which leads to the cross-linking of the PDMS components. We have tested the capability of the PDMS particles to remove toluene and benzene from water. We also performed similar experiments by utilizing PDMS sheets. In both instances we observed a rapid sorption of the organic phase into PDMS; the amount of absorbed organic solvent depended on the concentration in water and the total mass (volume) of PDMS and did not depend on the geometry of the PDMS “sponge.” In addition, we have examined the uptake of toluene and benzene from toluene/benzene (T/B) mixtures dissolved in water. Our results indicate that the amount of benzene absorbed from the T/B mixtures into PDMS increases relative to the uptake from pure benzene/water solutions. This behavior is associated with toluene acting as a “surfactant” that effectively replaces the more unfavorable PDMS/B contacts with less costly T/B ones. Finally, a simple experiment demonstrates qualitatively that PDMS is also capable of removing crude oils from oil-contaminated waters.}, number={3}, journal={JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY}, author={Park, Insun and Efimenko, Kirill and Sjoblom, Johan and Genzer, Jan}, year={2009}, pages={318–327} }
 @article{diamanti_arifuzzaman_genzer_vaia_2009, title={Tuning Gold Nanoparticle-Poly(2-hydroxyethyl methacrylate) Brush Interactions: From Reversible Swelling to Capture and Release}, volume={3}, ISSN={["1936-086X"]}, DOI={10.1021/nn800822c}, abstractNote={Tailoring the interaction between surfaces and nanoparticles (NPs) affords great opportunities for a range of applications, including sensors, information storage, medical diagnostics, and filtration membranes. In addition to controlling local ordering and microscale patterning of the NPs, manipulating the temporal factors determining the strength of the interaction between NP and surface enables dynamic modulation of these structural characteristics. In this contribution we demonstrate robust polymer brush-NP hybrids that exhibit both reversible swelling and reversible NP adsorption/desorption. Polymer brush functionality is tailored through post-functionalization of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes on flat solid substrates with alpha-amine conjugates ranging from perfluoro alkanes to poly(ethylene glycol) of varying molecular weights. The type of functionality controls NP affinity for the surfaces. In the case of poly(ethylene glycol) (PEG), the molecular weight (MW) of the PEG dictates adsorption and desorption phenomena. Higher MW PEG chains possess increased binding affinity toward NPs, which leads to higher relative Au-NP densities on the PHEMA-g-PEG brushes and concurrent sluggish desorption of NPs by thermal stimulus. Adsorption and desorption phenomena are further modulated by NP size yielding a system where adsorption and desorption are controlled by a delicate balance between the competitive energetics of polymer brush chelation versus solvation.}, number={4}, journal={ACS NANO}, author={Diamanti, Steve and Arifuzzaman, Shafi and Genzer, Jan and Vaia, Richard A.}, year={2009}, month={Apr}, pages={807–818} }
 @article{wei_gurr_gozen_blencowe_solomon_qiao_spontak_genzer_2008, title={Autophobicity-driven surface segregation and patterning of core-shell microgel nanoparticles}, volume={8}, ISSN={["1530-6992"]}, DOI={10.1021/nl802109x}, abstractNote={Core-shell microgel (CSMG) nanoparticles, also referred to as core-cross-linked star (CCS) polymers, can be envisaged as permanently cross-linked block copolymer micelles and, as such, afford novel opportunities for chemical functionalization, templating, and encapsulation. In this study, we explore the behavior of CSMG nanoparticles comprising a poly(methyl methacrylate) (PMMA) shell in molten PMMA thin films. Because of the autophobicity between the densely packed, short PMMA arms of the CSMG shell and the long PMMA chains in the matrix, the nanoparticles migrate to the film surface. They cannot, however, break through the surface because of the inherently high surface energy of PMMA. Similar thermal treatment of CSMG-containing PMMA thin films with a polystyrene (PS) capping layer replaces surface energy at the PMMA/air interface by interfacial energy at the PMMA/PS interface, which reduces the energy barrier by an order of magnitude, thereby permitting the nanoparticles to emerge out of the PMMA bulk. This nanoscale process is reversible and can be captured at intermediate degrees of completion. Moreover, it is fundamentally general and can be exploited as an alternative means by which to reversibly pattern or functionalize polymer surfaces for applications requiring responsive nanolithography.}, number={9}, journal={NANO LETTERS}, author={Wei, Bin and Gurr, Paul A. and Gozen, Arif O. and Blencowe, Anton and Solomon, David H. and Qiao, Greg G. and Spontak, Richard J. and Genzer, Jan}, year={2008}, month={Sep}, pages={3010–3016} }
 @article{genzer_marmur_2008, title={Biological and synthetic self-cleaning surfaces}, volume={33}, ISSN={["1938-1425"]}, DOI={10.1557/mrs2008.159}, abstractNote={AbstractIn this contribution, we briefly discuss how various physicochemical properties of surfaces affect the wettability and self-cleaning character of both naturally occurring and synthetic surfaces. Using a few selected examples from nature, we discuss the superhydrophobic effect and antifouling character of such surfaces and how these properties are associated with variations in surface chemical composition and topography. We also review a few special case studies aimed at adopting these biomimetic schemes to design and fabricate functional self-cleaning surfaces.}, number={8}, journal={MRS BULLETIN}, author={Genzer, Jan and Marmur, Abraham}, year={2008}, month={Aug}, pages={742–746} }
 @article{jhon_semler_genzer_2008, title={Effect of solvent quality and chain confinement on the kinetics of polystyrene bromination}, volume={41}, DOI={10.1021/ma8011653}, abstractNote={We report on the kinetics of the bromination of free polystyrene (PS) chains in bulk solution and those anchored on flat solid substrates by performing the bromination reaction in different solvents, including nitrobenzene (NB), 1-chlorodecane (CD), 1-chloroundecane (CUD), and 1-chlorododecane (CDD), at various temperatures. We find that bulk bromination of PS follows the second-order kinetic in bromine and the reaction rate increases with increasing dielectric constant of the solvent (e). In spite of eCDD > eCD, the bulk bromination kinetics of PS in CDD is slower than that in CD because of lower solubility of PS in CDD than in CD. In addition, we demonstrate that the reaction rates for brominating PS brushes anchored to flat solid substrates are much slower than those for brominating free PS chains in bulk solution. We attribute this behavior to steric hindrance due to PS confinement on the substrate.}, number={18}, journal={Macromolecules}, author={Jhon, Y. K. and Semler, J. J. and Genzer, Jan}, year={2008}, pages={6719–6727} }
 @article{gorman_petrie_genzer_2008, title={Effect of substrate geometry on polymer molecular weight and polydispersity during surface-initiated polymerization}, volume={41}, ISSN={["1520-5835"]}, DOI={10.1021/ma8004857}, abstractNote={Poly(methyl methacrylate) (PMMA) anchored chains were grown on porous silicon (p-Si) and anodically etched aluminum oxide (AAO) substrates via surface-initiated atom transfer radical polymerization (ATRP). Using hydrogen fluoride, the chains could be cleaved from the substrates, as evidenced by infrared spectroscopy. The molecular weights and molecular weight distributions of PMMA could be analyzed directly on these substrates (after cleaving the chains from the support) using direct ionization mass spectrometry (DIOS-MS) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Two principal conclusions were drawn from the study. First, matrix-free DIOS-MS was effective at direct analysis of the polymers up to a molecular weight of ≈6 kDa; the signal-to-noise ratio for heavier polymer chains diminished rapidly. Second, under the same polymerization conditions, PMMA grown on both p-Si and AAO substrates had a much lower molecular weight and a broader molecular weight distribution than ...}, number={13}, journal={MACROMOLECULES}, author={Gorman, Christopher B. and Petrie, Randall J. and Genzer, Jan}, year={2008}, month={Jul}, pages={4856–4865} }
 @article{crowe-willoughby_genzer_2009, title={Formation and Properties of Responsive Siloxane-Based Polymeric Surfaces with Tunable Surface Reconstruction Kinetics}, volume={19}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.200800622}, abstractNote={AbstractHere, the formation of responsive polymeric materials with tunable response time is reported. These structures are fabricated by chemically modifying poly(vinylmethyl siloxane) (PVMS) networks with alkanethiols bearing a hydrophilic end‐group (COOH or OH). The response time is facilitated by the liquid nature of the PVMS backbone and increases with increase in length of the methylene spacer (CH2)n in the alkanethiol pendent group. While for n = 2 and 6, the surface reconstructs almost instantaneously, specimens with n = 11 resist reconstruction because of strong van der Waals forces, leading to the formation of semi‐crystalline regions. It is demonstrated that the responsive nature of PVMSS(CH2)11OH can be fine‐tuned by varying the temperature; it possesses a faster response at temperatures above the melting point of the S(CH2)11OH moiety.}, number={3}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Crowe-Willoughby, Julie Ann and Genzer, Jan}, year={2009}, month={Feb}, pages={460–469} }
 @article{tomlinson_genzer_2008, title={Formation and properties of multivariant assemblies of surface-tethered diblock and triblock copolymers}, volume={49}, ISSN={["0032-3861"]}, DOI={10.1016/j.polymer.2008.08.048}, abstractNote={We present methodologies for fabricating block copolymer assemblies grafted onto flat solid substrates, where each block of the copolymer possesses a systematic and gradual variation of molecular weight as a function of the position on the substrate. We demonstrate the utility of this technique on two case studies. In the first project, we generate surface-tethered poly[(2-hydroxyethyl methacrylate)-b-(methyl methacrylate)] (PHEMA-b-PMMA) diblock copolymer brushes and study systematically morphological transitions associated with collapsing either the top PMMA or the bottom PHEMA block while keeping the other block solvated. Scanning force microscopy studies of systems having the top block collapsed reveal the presence of either flat (F), or micellar (M) or bicontinuous (BC) morphologies, whose locus in the phase diagram agrees with theoretical predictions and results of computer simulations. The second case study demonstrates the extension of the deposition method to the case of surface-anchored triblock copolymer brushes. Specifically, we present results pertaining to the formation of poly[(2-hydroxyethyl methacrylate)-b-(methyl methacrylate)-b-(dimethylaminoethyl methacrylate)] brushes with independent variation of all three block lengths.}, number={22}, journal={POLYMER}, author={Tomlinson, Michael R. and Genzer, Jan}, year={2008}, month={Oct}, pages={4837–4845} }
 @article{sivaniah_genzer_hexemer_kramer_xiang_li_ober_magonov_2008, title={Nonplanar Surface Organization of Monodendrons in Side-Chain Modified Liquid Crystalline Block Copolymers.}, volume={41}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ma8015097}, DOI={10.1021/ma8015097}, abstractNote={Scanning force microscopy (SFM) is used to investigate the surface structures of diblock copolymers of poly(styrene)-block-poly(isoprene) where a portion of the isoprene segments were modified to contain a semifluorinated alkane monodendron side group. The monodendrons consisted of either a single, double or triple attachment of the liquid crystalline mesogen group, [-(CH2)p-(CF2)qF]. Previously we reported that the surfaces of thin films of these materials contained small (∼20−30 nm) dome-like structures that were independent of the coincident block copolymer microphase architecture. We show here that these surface features can also assume a worm-like structure depending on the composition of the monodendron. Furthermore thermal studies of the block copolymer and the isolated monodendron molecule using in situ SFM studies confirm the liquid crystalline origin of the surface structures.}, number={24}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Sivaniah, E. and Genzer, J. and Hexemer, A. and Kramer, E. J. and Xiang, M. L. and Li, X. F. and Ober, C. K. and Magonov, S.}, year={2008}, month={Dec}, pages={9940–9945} }
 @article{diamanti_arifuzzaman_elsen_genzer_vaia_2008, title={Reactive patterning via post-functionalization of polymer brushes utilizing disuccinimidyl carbonate activation to couple primary amines}, volume={49}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2008.06.020}, abstractNote={Polymer brushes provide an exceptional route to surface functionalization due to their chemical and mechanical robustness, lack of large-area defects, and high density of functional groups. In spite of these benefits, the synthetic difficulty and complex surface structure associated with polymer brushes have hindered their utilization for constructing multifunctional, patterned surfaces. In this contribution we describe the use of a rapid and highly efficient polymer brush post-functionalization technique as a facile method for controlling surface functionality of polymer brushes. Poly(2-hydroxyethyl methacrylate) (PHEMA) brushes are post-functionalized via activation with N,N′-disuccinimidyl carbonate (DSC) and subsequent coupling to molecules containing α-amine moieties. This post-functionalization effectively tailors surface energy resulting in water contact angles ranging from 40° to 100° using different conjugate molecules. Furthermore, the solvent tolerance, insensitivity to reactant concentration, and rapid reaction time of the aminolysis reaction enable surface energy patterning of the polymer brushes through the use of "reactive" soft lithography. Finally, these surface energy patterns could be "developed" by exposure to gold nanoparticle solutions to yield surfaces with patterned nanoparticle density.}, number={17}, journal={POLYMER}, author={Diamanti, Steve and Arifuzzaman, Shafi and Elsen, Andrea and Genzer, Jan and Vaia, Richard A.}, year={2008}, month={Aug}, pages={3770–3779} }
 @article{strickland_hall_genzer_2008, title={Simulation of mechanically assembled monolayers and polymers in good solvent using discontinuous molecular dynamics}, volume={41}, ISSN={["0024-9297"]}, DOI={10.1021/ma8003218}, abstractNote={We present the results of discontinuous molecular dynamics simulations of mechanically assembled monolayers in good solvent. Polymers of chain lengths 5−100 were end-grafted to surfaces at low density and then compressed laterally at varying rates. Data for brush thickness and end-monomer density were collected as a function of surface density; they were shown to correspond well with theoretical predictions and simulation results performed at constant surface density. Brush thickness for all chain lengths could be controlled by judicious choice of the compression rate. Defects in the brush layer were dependent on chain length; it was shown that quick compression for relatively short chains allowed the layer no time to relax into coil form. Quick compression on long chain systems led to entanglement in the brush layer since the longer-chained system was not being afforded the long relaxation time required to form a fully relaxed brush. Hysteresis effects were examined by allowing the brush to relax to a lo...}, number={17}, journal={MACROMOLECULES}, author={Strickland, L. Anderson and Hall, Carol K. and Genzer, Jan}, year={2008}, month={Sep}, pages={6573–6581} }
 @article{ritz_látalová_kříž_genzer_vlček_2008, title={Statistical copolymers of 2-(trimethylsilyloxy)ethyl methacrylate and methyl methacrylate synthesized by ATRP}, volume={46}, ISSN={0887-624X 1099-0518}, url={http://dx.doi.org/10.1002/pola.22436}, DOI={10.1002/pola.22436}, abstractNote={AbstractNo Abtract.}, number={5}, journal={Journal of Polymer Science Part A: Polymer Chemistry}, publisher={Wiley}, author={Ritz, Pavel and Látalová, Petra and Kříž, Jaroslav and Genzer, Jan and Vlček, Petr}, year={2008}, pages={1919–1923} }
 @misc{genzer_bhat_2008, title={Surface-bound soft matter gradients}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la7033164}, abstractNote={This feature article describes the progress realized over the past half century in the field of surface-bound gradient structures created on or from soft materials (oligomers and/or polymers), or those enabling the study of the behavior of soft materials. By highlighting our work in the field and accounting for the contribution of other groups, we emphasize the exceptional versatility of gradient assemblies in facilitating fast screening of physicochemical phenomena, acting as "recording media" for monitoring a process, and playing a key role in the design and fabrication of surface-bound molecular and macromolecular motors capable of directing a transport phenomenon.}, number={6}, journal={LANGMUIR}, author={Genzer, Jan and Bhat, Rajendra R.}, year={2008}, month={Mar}, pages={2294–2317} }
 @article{guo_resnick_efimenko_genzer_desimone_2008, title={Alternative fluoropolymers to avoid the challenges associated with perfluorooctanoic acid}, volume={47}, ISSN={["0888-5885"]}, DOI={10.1021/ie0703179}, abstractNote={The degradation of stain-resistant coating materials leads to the release of biopersistent perfluorooctanoic acid (PFOA) to the environment. In order to find the environmentally friendly substitutes, we have designed and synthesized a series of nonbiopersistant fluorinated polymers containing perfluorobutyl groups in the side chains. The surface properties of the new coating materials were characterized by static and dynamic contact angle measurements. The new coating materials demonstrate promising hydrophobic and oleophobic properties with low surfaces tensions. The wetting properties and surface structure of the polymers were tuned by varying the “spacer” structures between the polymer backbones and the perfluorinated groups of the side chains. The relationship between orientations of the fluorinated side chains and performances of polymer surfaces were further investigated by near-edge X-ray fine absorption structure (NEXAFS) experiments and differential scanning calorimetry (DSC).}, number={3}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Guo, Ji and Resnick, Paul and Efimenko, Kirill and Genzer, Jan and DeSimone, Joseph M.}, year={2008}, month={Feb}, pages={502–508} }
 @article{wu_gong_szleifer_vlcek_subr_genzer_2007, title={Behavior of surface-anchored poly(acrylic acid) brushes with grafting density gradients on solid substrates: 1. Experiment}, volume={40}, ISSN={["1520-5835"]}, DOI={10.1021/ma0710176}, abstractNote={We describe experiments pertaining to the formation of surface-anchored poly(acrylic acid) (PAA) brushes with a gradual variation of the PAA grafting densities on flat surfaces and provide detailed analysis of their properties. The PAA brush gradients are generated by first covering the substrate with a molecular gradient of the polymerization initiator, followed by the “grafting from” polymerization of tert-butyl acrylate (tBA) from these substrate-bound initiator centers, and finally converting the PtBA into PAA. We use spectroscopic ellipsometry to measure the wet thickness of the grafted PAA chains in aqueous solutions at three different pH values (4, 5.8, and 10) and a series of ionic strengths (IS). Our measurements reveal that at low grafting densities, σ, the wet thickness of the PAA brush (H) remains relatively constant, the polymers are in the mushroom regime. Beyond a certain value of σ, the macromolecules enter the brush regime, where H increases with increasing σ. For a given σ, H exhibits a ...}, number={24}, journal={MACROMOLECULES}, author={Wu, Tao and Gong, Peng and Szleifer, Igal and Vlcek, Petr and Subr, Vladimir and Genzer, Jan}, year={2007}, month={Nov}, pages={8756–8764} }
 @article{gong_wu_genzer_szleifer_2007, title={Behavior of surface-anchored poly(acrylic acid) brushes with grafting density gradients on solid substrates: 2. Theory}, volume={40}, ISSN={["0024-9297"]}, DOI={10.1021/ma071018y}, abstractNote={We apply a molecular theory to predict the structural properties of poly(acrylic acid) macromolecules grafted via one of their ends to solid surfaces. The theory explicitly incorporates the acid-base equilibrium responsible for the charge regulation of the acrylic groups, as well as the conformations, size, shape, and charge distributions of all the molecular species present. We compare the predictions of the theory with experimental observations presented in the preceding article for the height of the layer as a function of ionic strength for different polymer molecular weight and polymer surface coverage. The calculated heights are found to be in good agreement with the experimental observations. The theory predicts the distribution of charges within the layer. We find that the counterions adsorb to the grafting surface, overcompensating the charge of the polymer. The charge regulation within the polymer layer is determined by the interplay between the bulk pH, the ionic strength, and the density of polymer. The system tends to become uncharged with decreasing ionic strength of the solution and increasing polymer density. In all cases the charge regulation acts in order to minimize the electrostatic repulsions in the system. The local distribution of protons within the polymer layer is predicted to be very different from that of the bulk solution. The local pH within the polymer layer can be tuned by varying the solution ionic strength and the polymer surface coverage; the variation can be large as two pH units, relative to the bulk pH. This large variation of the local pH within a couple of nanometers within the brush can be used in the design of biosensors.}, number={24}, journal={MACROMOLECULES}, author={Gong, Peng and Wu, Tao and Genzer, Jan and Szleifer, Igal}, year={2007}, month={Nov}, pages={8765–8773} }
 @article{rhodes_lappi_fischer_sambasivan_genzer_franzen_2008, title={Characterization of monolayer formation on aluminum-doped zinc oxide thin films}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la701741m}, abstractNote={The optical and electronic properties of aluminum-doped zinc oxide (AZO) thin films on a glass substrate are investigated experimentally and theoretically. Optical studies with coupling in the Kretschmann configuration reveal an angle-dependent plasma frequency in the mid-IR for p-polarized radiation, suggestive of the detection of a Drude plasma frequency. These studies are complemented by oxygen depletion density functional theory studies for the calculation of the charge carrier concentration and plasma frequency for bulk AZO. In addition, we report on the optical and physical properties of thin film adlayers of n-hexadecanethiol (HDT) and n-octadecanethiol (ODT) self-assembled monolayers (SAMs) on AZO surfaces using reflectance FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Our characterization of the SAM deposition onto the AZO thin film reveals a range of possible applications for this conducting metal oxide.}, number={2}, journal={LANGMUIR}, author={Rhodes, Crissy L. and Lappi, Simon and Fischer, Daniel and Sambasivan, Sharadha and Genzer, Jan and Franzen, Stefan}, year={2008}, month={Jan}, pages={433–440} }
 @article{jayaraman_hall_genzer_2007, title={Computer simulation study of probe-target hybridization in model DNA microarrays: Effect of probe surface density and target concentration}, volume={127}, ISSN={["1089-7690"]}, DOI={10.1063/1.2787618}, abstractNote={We use lattice Monte Carlo simulations to study the thermodynamics of hybridization of single-stranded “target” genes in solution with complementary “probe” DNA molecules immobilized on a microarray surface. The target molecules in our system contain 48 segments and the probes tethered on a hard surface contain 8–24 segments. The segments on the probe and target are distinct, with each segment representing a sequence of nucleotides that interacts exclusively with its unique complementary target segment with a single hybridization energy; all other interactions are zero. We examine how surface density (number of probes per unit surface area) and concentration of target molecules affect the extent of hybridization. For short probe lengths, as the surface density increases, the probability of binding long stretches of target segments increases at low surface density, reaches a maximum at an intermediate surface density, and then decreases at high surface density. Furthermore, as the surface density increases, the target is less likely to bind completely to one probe; instead, it binds simultaneously to multiple probes. At short probe lengths, as the target concentration increases, the fraction of targets binding completely to the probes (specificity) decreases. At long probe lengths, varying the target concentration does not affect the specificity. At all target concentrations as the probe length increases, the fraction of target molecules bound to the probes by at least one segment (sensitivity) increases while the fraction of target molecules completely bound to the probes (specificity) decreases. This work provides general guidelines to maximizing microarray sensitivity and specificity. Our results suggest that the sensitivity and specificity can be maximized by using probes 130–180 nucleotides long at a surface density in the range of 7×10−5–3×10−4probemoleculespernm2.}, number={14}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Jayaraman, Arthi and Hall, Carol K. and Genzer, Jan}, year={2007}, month={Oct} }
 @article{semler_jhon_tonelli_beevers_krishnamoorti_genzer_2007, title={Facile method of controlling monomer sequence distributions in random copolymers}, volume={19}, DOI={10.1002/adma.200602359}, abstractNote={Inthis report, we present a simple methodology facilitating theformation of A-B random copolymers with tunable sequencedistributions. We demonstrate that varying the degree ofblockiness in the sequence distribution of A and B monomershas a profound impact on the partition of random copolymersat interfaces.Random copolymers (RCPs) are long chain moleculesmade of covalently bound monomers comprising at least twodifferent chemical moieties (say, A and B). In addition to theoverall molecular weight, RCPs are characterized by theircomposition and monomer sequence distribution. The abilityof A-B RCPs to act as “homopolymers with tunable composi-tion”, ranging between A and B homopolymers, has recentlyattracted considerable attention in controlling polymer misci-bility}, number={19}, journal={Advanced Materials}, author={Semler, J. J. and Jhon, Y. K. and Tonelli, A. and Beevers, M. and Krishnamoorti, R. and Genzer, Jan}, year={2007}, pages={2877-} }
 @article{cerruti_rhodes_losego_efremenko_maria_fischer_franzen_genzer_2007, title={Influence of indium-tin oxide surface structure on the ordering and coverage of carboxylic acid and thiol monolayers}, volume={40}, ISSN={["1361-6463"]}, DOI={10.1088/0022-3727/40/14/016}, abstractNote={This paper analyses the variability of self-assembled monolayers (SAMs) formation on ITO depending on the substrate surface features. In particular, we report on the formation of carboxylic acid- and thiol-based SAMs on two lots of commercially prepared indium–tin oxide (ITO) thin films. Contact angle measurements, electrochemical experiments, and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy showed that the quality of monolayers formed differed substantially between the two ITO batches. Only one of the two ITO substrates was capable of forming well-organized thiol- and carboxylic acid-based SAMs. In order to rationalize these observations, atomic force microscopy and x-ray diffraction analyses were carried out, and SAMs were prepared on ITO substrates fabricated by sputtering in our laboratories. An attempt was made to influence the film microstructure and surface morphology by varying substrate temperatures during ITO deposition. Good-quality thiol and carboxylic acid SAMs were obtained on one of the ITO substrates prepared in-house. While our characterization could not single out conclusively one specific parameter in ITO surface structure that could be responsible for good SAMs formation, we could point out homogeneous surface morphology as a relevant factor for the quality of the SAMs. Evidence was also found for ITO crystallographic orientation to be a parameter influencing SAMs organization.}, number={14}, journal={JOURNAL OF PHYSICS D-APPLIED PHYSICS}, author={Cerruti, Marta and Rhodes, Crissy and Losego, Mark and Efremenko, Alina and Maria, Jon-Paul and Fischer, Daniel and Franzen, Stefan and Genzer, Jan}, year={2007}, month={Jul}, pages={4212–4221} }
 @article{loo_genzer_2007, title={Introduction}, volume={45}, ISSN={["0887-6266"]}, DOI={10.1002/polb.21356}, abstractNote={Fifteen years in its tradition, the December issue of the Journal of Polymer Science, Polymer Physics features a series of papers by members of the Division of Polymers (DPOLY) who presented their work at the annual meeting of the American Physical Society (APS). Two years ago, this special APS DPOLY issue received a significant “face-lift.” Kari Dalnoki-Veress (recipient of the 2008 Dillon Medal) from McMaster University in Canada, who served as the Editor of the special issue, introduced a new and exciting layout which incorporated a series of feature articles by invited authors1 in addition to regular contributed papers. In these feature articles, experts in their respective fields shared their points-of-views on current and future developments in polymer physic related topics; these articles were meant to provide perspective to non-experts in the field. Additionally, the winners of the Polymer Physics Prize and the Dillon Medal wrote review articles pertaining to their research. This fresh blueprint introduced by Kari made a very favorable impression on the readers of the journal and a similar format was chosen by the co-editors of the special issue last year, Chang Y. Ryu and Rahmi Ozisik from the Rensselaer Polytechnic Institute, the following year.2 Inspired by our predecessors and by the success of the new format of the special APS issue, the decision for us to replicate the existing layout was thus very easy. The 2007 DPOLY special issue of Journal of Polymer Science, Polymer Physics highlights a paper co-authored by Glenn Fredrickson, the winner of the 2007 DPOLY Polymer Physics Prize. Concentrating on recent advances in the simulation of charged polymeric systems, Glenn's review article provides an excellent overview of the field, which we hope will inspire theorists and experimentalists alike. The subsequent 6 articles represent viewpoints/opinions by experts in the diverse fields of polymer physics. The section commences with a paper authored by Buck Christ, who commemorates the 50th anniversary of chain folding. Steve Granick and Janet Wong share their perspectives on friction in polymer systems. Ron Larson's article examines entanglements in polymer dynamics by computer simulations. Marc Hillmyer highlights the influence of molecular weight distribution on microstructure development in block copolymers. New insights into polymer nanocomposites are presented by Ramanan Krishnamoorti and Rich Vaia. And if you ever wondered how polymer physics is related to foodstuffs, you should not miss Athene Donald's article. The second part of the journal features 13 contributed papers, including several from finalists of the Frank J. Padden, Jr. Award, highlighting selected works presented during the March 2007 APS meeting. It has been our pleasure to co-edit the 2007 special issue of Journal of Polymer Science, Polymer Physics. We would like to take this opportunity to thank the authors for their contributions and the reviewers for their assistance in assessing these manuscripts. And last but not least, we would like to express our sincere gratitude to Ms. Hope Inman, the journal's managing editor, for her help and superb organization and managing skills. Enjoy! YUEH-LIN (LYNN) LOO Professor Loo recently joined Princeton University as an associate professor in the Chemical Engineering Department. She received bachelor degrees in Chemical Engineering as well as Materials Science and Engineering from the University of Pennsylvania in 1996 and a doctoral degree in Chemical Engineering from Princeton University in 2001. In 2002, Lynn joined the University of Texas at Austin as Assistant Professor in Chemical Engineering and General Dynamics Endowed Faculty Fellow in Engineering. Lynn's research focuses on developing patterning and processing tools for making organic electronic devices and understanding the structure-property relationships in organic electrically-active materials, especially solution-processable organic molecular semiconductors and polymer conductors. Her honors include a Camille and Henry Dreyfus New Faculty Award (2002), a DuPont Young Professor Grant (2003), an NSF-CAREER Award (2004), and an Arnold and Mabel Beckman Young Investigator Award (2005). In 2004, Lynn was also selected as one of Top 100 Young Innovators under 35 by MIT's Technology Review. More recently, Lynn was the inaugural recipient of the Peter and Edith O'Donnell Award in Engineering awarded by the Academy of Medicine, Science, and Engineering of Texas and the 2006 recipient of the Alan P. Colburn Award of the AIChE. Lynn will be presenting the 2007 Thiele Lecture in the Chemical Engineering Department at the University of Notre Dame this fall. JAN GENZER Professor Genzer is a professor of Chemical & Biomolecular Engineering at North Carolina State University. He received the "Diploma-engineer" degree (Dipl.-Ing.) in Chemical & Materials Engineering from the Institute of Chemical Technology in Prague, Czech Republic in 1989 and Ph.D. in Materials Science & Engineering from the University of Pennsylvania in 1996. Between 1996 and 1998 he was a post-doctoral fellow at Cornell University and the University of California at Santa Barbara, working with Professor Ed Kramer. In the fall 1998 he joined the faculty of chemical engineering at the North Carolina State University as an assistant professor and was promoted to the associate and full professor in 2004 and 2006, respectively. He also holds a position of an adjunct professor at the Norwegian University of Science & Technology (NTNU) in Trondheim, Norway. His honors include: Camille Dreyfus Teacher-Scholar Award, Sigma Xi research award, NSF CAREER award, John H. Dillon Award of the American Physical Society, NSF Award for Special Creativity, and NCSU's Outstanding Teacher award. He has published over 100 peer-reviewed journal articles and delivered more than 100 invited lectures. His group at North Carolina State University is actively involved in research related to the behavior of polymers at interfaces and in confined geometries, with particular emphasis on self-assembly and forced assembly and combinatorial methods.}, number={24}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Loo, Yueh-Lin and Genzer, Jan}, year={2007}, month={Dec}, pages={3221–3222} }
 @inproceedings{crowe_efimenko_genzer_2007, title={Manipulating siloxane surfaces: Obtaining the desired surface function via engineering design}, volume={964}, DOI={10.1021/bk-2007-0964.ch015}, abstractNote={We present a synopsis of recent accomplishment in our group in the area of surface-functionalized silicone elastomer networks. Specifically, we show that by combining mechanical manipulation of poly(dimethylsiloxane) (PDMS) networks with activation via ultraviolet/ozone (UVO) treatment and subsequent chemical modification of the preactivated surfaces, one can generate so-called mechanically assembled monolayers (MAMs). This technology can be successfully applied to create a variety of surfaces, including dense polymer brushes, long-lived superhydrophobic surfaces, molecular gradients comprising tunable length scales and two-dimensional chemical gradients. In addition, the UVO modification of mechanically strained PDMS sheets provides a convenient route for creating "buckled" elastomeric sheets. These surfaces have a multitude of applications; ranging from anti-fouling surfaces to directed particle assembly. Finally we demonstrate control of surface wettability and responsiveness using poly(vinylmethylsiloxane) (PVMS) networks. We have shown that PVMS surfaces can be chemically tailored by reacting with thiols. The degree of response (including response rate) of such surfaces to hydrophobic-hydrophilic interactions can be adjusted by varying the chemical and structural properties of the side-group modifiers.}, booktitle={Science and technology of silicones and silicone-modified materials}, author={Crowe, J. A. and Efimenko, Kirill and Genzer, Jan}, year={2007}, pages={222–255} }
 @misc{liebmann-vinson_chaney_efimenko_genzer_2007, title={Methods of surface modification of a flexible substrate to enhance cell adhesion}, volume={7,198,855}, number={2007 Apr. 7}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Liebmann-Vinson, A. and Chaney, B. and Efimenko, K. and Genzer, J.}, year={2007} }
 @article{schultz_hall_genzer_2007, title={Obtaining concentration profiles from computer simulation structure factors}, volume={40}, ISSN={["1520-5835"]}, DOI={10.1021/ma062836d}, abstractNote={The structure factor, S(q), is an important analysis tool for analyzing the structure of macromolecular crystals, 1,2 block copolymers, 3 micelles, 4 and the glass transition. 5 As the Fourier transform of the density profile, S(q) gives a quantitative description of the concentration fluctuations in a system as a function of the fluctuation frequency and direction. S(q) can be obtained experimentally from scattering experiments or can be extracted from simulation data on particle positions. In the past,S(q) has been used to determine the size and morphology of micelles, the degree of ordering, the identity of an ordered structure, and even the interaction strength between components of a copolymer. 6-8}, number={8}, journal={MACROMOLECULES}, author={Schultz, Andrew J. and Hall, Carol K. and Genzer, Jan}, year={2007}, month={Apr}, pages={2629–2632} }
 @article{gong_genzer_szleifer_2007, title={Phase behavior and charge regulation of weak polyelectrolyte grafted layers}, volume={98}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.98.018302}, abstractNote={The stability of weak polyelectrolytes end grafted to a planar surface has been studied with a molecular theory. The effective quality of the solvent is found to depend on the interplay between polymer grafting density, acid-base equilibrium, and salt concentration. Our results reveal that increasing salt concentration results in a thermodynamically more stable layer. This reverse salt effect is due to the competition between the solvent quality and the dual role of the ionic strength in screening the electrostatic interactions (reducing stability with increasing salt concentration), and regulating the charge on the polymer (increasing charge with increasing salt concentration). Grafted weak polyelectrolyte layers are found to be thermodynamically unstable at intermediate surface coverages. Additionally, it is established that the increased solubility of the layer at low surface coverage is due to the relatively large charge of the grafted polymers. The range of stability of the film with regard to polymer surface coverage, temperature, bulk pH and salt concentration is demonstrated.}, number={1}, journal={PHYSICAL REVIEW LETTERS}, author={Gong, Peng and Genzer, Jan and Szleifer, I.}, year={2007}, month={Jan} }
 @article{douglas_efimenko_fischer_phelan_genzer_2007, title={Propagating waves of self-assembly in organosilane monolayers}, volume={104}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0703620104}, abstractNote={
            Wavefronts associated with reaction–diffusion and self-assembly processes are ubiquitous in the natural world. For example, propagating fronts arise in crystallization and diverse other thermodynamic ordering processes, in polymerization fronts involved in cell movement and division, as well as in the competitive social interactions and population dynamics of animals at much larger scales. Although it is often claimed that self-sustaining or autocatalytic front propagation is well described by mean-field “reaction–diffusion” or “phase field” ordering models, it has recently become appreciated from simulations and theoretical arguments that fluctuation effects in lower spatial dimensions can lead to appreciable deviations from the classical mean-field theory (MFT) of this type of front propagation. The present work explores these fluctuation effects in a real physical system. In particular, we consider a high-resolution near-edge x-ray absorption fine structure spectroscopy (NEXAFS) study of the spontaneous frontal self-assembly of organosilane (OS) molecules into self-assembled monolayer (SAM) surface-energy gradients on oxidized silicon wafers. We find that these layers organize from the wafer edge as propagating wavefronts having well defined velocities. In accordance with two-dimensional simulations of this type of front propagation that take fluctuation effects into account, we find that the interfacial widths
            w
            (
            t
            ) of these SAM self-assembly fronts exhibit a power-law broadening in time,
            w
            (
            t
            ) ≈
            t
            β
            , rather than the constant width predicted by MFT. Moreover, the observed exponent values accord rather well with previous simulation and theoretical estimates. These observations have significant implications for diverse types of ordering fronts that occur under confinement conditions in biological or materials-processing contexts.
          }, number={25}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Douglas, Jack F. and Efimenko, Kirill and Fischer, Daniel A. and Phelan, Fredrick R. and Genzer, Jan}, year={2007}, month={Jun}, pages={10324–10329} }
 @article{kim_efimenko_genzer_carbonell_2007, title={Surface properties of poly[2-(perfluorooctyl)ethyl acrylate] deposited from liquid CO2 high-pressure free meniscus coating}, volume={40}, ISSN={["1520-5835"]}, DOI={10.1021/ma0623791}, abstractNote={The surface characteristics of poly[2-(perfluorooctyl)ethyl acrylate] (PFOEA) films deposited using a high-pressure free meniscus coating (hFMC) process with liquid CO{sub 2} (l-CO{sub 2}) as the coating solvent on 12.5 cm diameter silicon wafer substrates were investigated using contact angle measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy. The results were compared with surface property measurements of PFOEA films deposited from 1,1,2-trichlorotrifluoroethane (Freon 113) under normal dip coating conditions at atmospheric pressure. NEXAFS measurements showed that perfluoroalkyl groups in the films from l-CO{sub 2} and Freon 113 were well-organized and oriented normal to the substrate at the air/polymer interface. AFM images and XPS measurements revealed that a terrace-like structure of the PFOEA film from l-CO{sub 2} resulted in carbonyl group exposure at the air/polymer interface. This leads to smaller contact angles on the films cast from l-CO{sub 2} relative to the specimens deposited from Freon 113. Annealing the films deposited from the solvents resulted in droplet formation on the surface due to dewetting. The critical surface tension ({gamma}{sub c}) after annealing the film prepared from Freon 113 increased from 6.5 to 8.5 mJ/m{sup 2}, whereas {gamma}{sub c} of the film deposited frommore » l-CO{sub 2} decreased slightly from 9.7 to 8.9 mJ/m{sup 2}. We discuss how surface morphology changes before and after annealing play a role in the variation of {gamma}{sub c}.« less}, number={3}, journal={MACROMOLECULES}, author={Kim, Jaehoon and Efimenko, Kirill and Genzer, Jan and Carbonell, Ruben G.}, year={2007}, month={Feb}, pages={588–597} }
 @article{ritz_latalova_janata_toman_kriz_genzer_vlcek_2007, title={Synthesis of amphiphilic copolymers by ATRP initiated with a bifunctional initiator containing trichloromethyl groups}, volume={67}, ISSN={["1873-166X"]}, DOI={10.1016/j.reactfunctpolym.2007.06.007}, abstractNote={Bifunctional polystyrene macroinitiators, having various molecular weights, were prepared by atom transfer radical polymerization (ATRP), initiated with bifunctional initiator 1,3-bis{1-methyl-1[(2,2,2-trichloroethoxy) carbonylamino]ethyl}benzene in conjunction with CuCl catalyst and polyamine ligands. These macroinitiators were subsequently used for ATRP of tert-butyl acrylate (t-BuA), giving BAB triblocks poly[(t-BuA)-b-(Sty)-b-(t-BuA)] as precursors of amphiphilic copolymers. Both the polymerization steps proceeded as controlled processes with linear semi-logarithmic conversion plots and lengths of the blocks following theoretical predictions. Hydrolysis of outer poly(t-BuA) blocks led to triblock copolymers with the central polystyrene block and outer blocks of poly(acrylic acid), the molecular weights of which ranged from ca. 5 × 103 to almost 1 × 105 Da.}, number={10}, journal={REACTIVE & FUNCTIONAL POLYMERS}, author={Ritz, P. and Latalova, P. and Janata, M. and Toman, L. and Kriz, J. and Genzer, J. and Vlcek, P.}, year={2007}, month={Oct}, pages={1027–1039} }
 @article{jayaraman_santiso_hall_genzer_2007, title={Theoretical study of kinetics of zipping phenomena in biomimetic polymers}, volume={76}, ISSN={["1550-2376"]}, DOI={10.1103/physreve.76.011915}, abstractNote={In this work we use theory to obtain a mathematical expression for a time correlation function c(l,t) that provides insight into the zipping phenomena along a polymer going through a conformational transition. The polymer is modeled as an Ising-like chain with each segment being in one of two states: bound (+1) or unbound (-1). The time correlation function c(l,t) predicts the correlation between the state of the jth polymer segment at time 0 and the state of the (j+/-l)th polymer segment at time t . The expressions for c(0,t) , c(1,t), and c(2,t) obtained from our theory are dependent on the values of k0 and k1, where 2k0 is the rate coefficient for one segment changing from an unbound state to a bound state when both the neighboring segments are in an unbound state, and 2k1 is the rate coefficient for one segment changing from an unbound state to a bound state when both the neighboring segments are in a bound state. The ratio k1/k0 is an indication of the extent of cooperativity of binding adjacent segments on the polymer. We observe that c(0,t), c(1,t), and c(2,t) decay to 0 (no correlation) more slowly and the maximum values of c(1,t) and c(2,t) are lower for low values of k1/k0 as compared to high values of k1/k0. This is because at low values of k1/k0 the consecutive binding of adjacent segments along the polymer occurs slowly, while at high values of k1/k0 the cooperativity of binding adjacent segments is high and the segments along the polymer bind in a fast zipping mechanism.}, number={1}, journal={PHYSICAL REVIEW E}, author={Jayaraman, Arthi and Santiso, Erik E. and Hall, Carol K. and Genzer, Jan}, year={2007}, month={Jul} }
 @article{jayaraman_hall_genzer_2006, title={Computer Simulation Study of Molecular Recognition in Model DNA Microarrays}, volume={91}, ISSN={0006-3495}, url={http://dx.doi.org/10.1529/biophysj.106.086173}, DOI={10.1529/biophysj.106.086173}, abstractNote={DNA microarrays have been widely adopted by the scientific community for a variety of applications. To improve the performance of microarrays there is a need for a fundamental understanding of the interplay between the various factors that affect microarray sensitivity and specificity. We use lattice Monte Carlo simulations to study the thermodynamics and kinetics of hybridization of single-stranded target genes in solution with complementary probe DNA molecules immobilized on a microarray surface. The target molecules in our system contain 48 segments and the probes tethered on a hard surface contain 8-24 segments. The segments on the probe and target are distinct and each segment represents a sequence of nucleotides ( approximately 11 nucleotides). Each probe segment interacts exclusively with its unique complementary target segment with a single hybridization energy; all other interactions are zero. We examine how the probe length, temperature, or hybridization energy, and the stretch along the target that the probe segments complement, affect the extent of hybridization. For systems containing single probe and single target molecules, we observe that as the probe length increases, the probability of binding all probe segments to the target decreases, implying that the specificity decreases. We observe that probes 12-16 segments ( approximately 132-176 nucleotides) long gave the highest specificity and sensitivity. This agrees with the experimental results obtained by another research group, who found an optimal probe length of 150 nucleotides. As the hybridization energy increases, the longer probes are able to bind all their segments to the target, thus improving their specificity. The hybridization kinetics reveals that the segments at the ends of the probe are most likely to start the hybridization. The segments toward the center of the probe remain bound to the target for a longer time than the segments at the ends of the probe.}, number={6}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Jayaraman, Arthi and Hall, Carol K. and Genzer, Jan}, year={2006}, month={Sep}, pages={2227–2236} }
 @article{jhon_bhat_jeong_rojas_szleifer_genzer_2006, title={Cover Picture: Macromol. Rapid Commun. 9/2006}, volume={27}, ISSN={1022-1336 1521-3927}, url={http://dx.doi.org/10.1002/marc.200690014}, DOI={10.1002/marc.200690014}, abstractNote={Cover: Quartz crystal microbalance with dissipation monitoring is used to probe the effect of salt concentration on the phase transition behavior of thermoresponsive surface‐grafted poly(N‐isopropylacryl‐amide) (PNIPAM) brushes brushes. The phase transition temperature of grafted polymer is found to decrease as the concentration of salt is increased. This depression in phase transition temperature is similar to that observed for free polymer and is attributed to unbinding of the water molecules from the PNIPAM by the presence of ions. Further details can be found in the article by Y. K. Jhon, R. R. Bhat, C. Jeong, O. J. Rojas, I. Szleifer, and J. Genzer* on page 697.}, number={9}, journal={Macromolecular Rapid Communications}, publisher={Wiley}, author={Jhon, Young K. and Bhat, Rajendra R. and Jeong, Changwoo and Rojas, Orlando J. and Szleifer, Igal and Genzer, Jan}, year={2006}, month={May}, pages={645–645} }
 @article{semler_genzer_2006, title={Design of random copolymers with statistically controlled monomer sequence distributions via Monte Carlo simulations}, volume={125}, ISSN={["1089-7690"]}, DOI={10.1063/1.2210011}, abstractNote={We use Monte Carlo simulations to model the formation of random copolymers with tunable monomer sequence distributions. Our scheme is based on the original idea proposed a few years ago by Khokhlov and Khalatur [Physica A 249, 253 (1998); Phys. Rev. Lett. 82, 3456 (1999)], who showed that the distribution of species B in A-B random copolymers can be regulated by (a) adjusting the coil size of a homopolymer A and (b) chemically modifying (“coloring”) monomers that reside at (or close to) the periphery of the coil with species B. In contrast to Khokhlov and Khalatur’s work, who modeled the polymer modification by performing the coloring instantaneously, we let the chemical coloring reaction progress over time using computer simulations. We show that similar to Khokhlov and Khalatur’s work, the blockiness (i.e., number of consecutive monomers) of the B species along the A-B copolymer increases with increasing degree of collapse of the parent homopolymer A. A simple analysis of the A-B monomer sequences in the copolymers reveals that monomer sequence distributions in homopolymers “colored” under collapsed conformations possess certain degrees of self-similarity, while there is no correlation found among the monomer sequence distributions formed by coloring homopolymers with expanded conformations.}, number={1}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Semler, James J. and Genzer, Jan}, year={2006}, month={Jul} }
 @article{smith_tong_genzer_fischer_kilpatrick_2006, title={Effects of synthetic amphiphilic alpha-helical peptides on the electrochemical and structural properties of supported hybrid bilayers on gold}, volume={22}, ISSN={["0743-7463"]}, DOI={10.1021/la051104w}, abstractNote={Amphiphilic alpha-helices were formed from designed synthetic peptides comprising alanine, phenylalanine, and lysine residues. The insertion of the alpha-helical peptides into hybrid bilayers assembled on gold was studied by a variety of methods to assess the resulting structural characteristics, such as electrical resistance and molecular orientation. Self-assembled monolayers (SAMs) of dodecanethiol (DDT); octadecanethiol (ODT); and 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) were formed on gold substrates with and without incorporated peptide. Supported hybrid bilayers and multilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were formed on SAMs by the "paint-freeze" method of bilayer formation. Modeling of electrochemical impedance spectroscopy data using equivalent electrochemical circuits revealed that the addition of peptide decreased dramatically the resistive element of the bilayer films while maintaining the value of the capacitive element, indicating successful incorporation of peptide into a well-formed bilayer. Near-edge X-ray absorption fine structure spectroscopy data provided evidence that the molecules in the SAMs and hybrid multilayers were ordered even in the presence of peptide. The peptide insertion into the SAM was confirmed by observing the pi* resonance peak correlating with phenylalanine and a peak in the nitrogen K-edge regime attributable to the peptide bond.}, number={4}, journal={LANGMUIR}, author={Smith, MB and Tong, JH and Genzer, J and Fischer, D and Kilpatrick, PK}, year={2006}, month={Feb}, pages={1919–1927} }
 @article{genzer_efimenko_fischer_2006, title={Formation mechanisms and properties of semifluorinated molecular gradients on silica surfaces}, volume={22}, ISSN={["0743-7463"]}, DOI={10.1021/la061016r}, abstractNote={The goal of this study is to elucidate the formation of molecular gradients made of semifluorinated organosilanes (SFOs) on flat substrates by using a methodology developed by Chaudhury and Whitesides (Science 1992, 256, 1539). We use surface-sensitive combinatorial near-edge X-ray absorption fine structure (combi-NEXAFS) spectroscopy to measure the position-dependent concentration and orientation of SFO molecules in SFO molecular gradients on flat silica surfaces. Using the combi-NEXAFS data, we establish the correlation between the fraction of the F(CF(2))(8)(CH(2))(2)- species on the substrate and the average tilt angle of the -(CF(2))(8)F group in the SFO as a function of the deposition gas medium (air vs nitrogen) and the end group around the silicon atom (monofunctional vs trifunctional). In addition, we utilize the gradient geometry to comprehend the mechanism of formation of SFO self-assembled monolayers (SAMs). Specifically, we provide evidence that depending on the nature of the end group in the SFO and the vapor phase the SFO molecules add themselves into the existing SAMs either as individual molecules or as multimolecular complexes.}, number={20}, journal={LANGMUIR}, author={Genzer, Jan and Efimenko, Kirill and Fischer, Daniel A.}, year={2006}, month={Sep}, pages={8532–8541} }
 @article{genzer_2006, title={In silico polymerization: Computer simulation of controlled radical polymerization in bulk and on flat surfaces}, volume={39}, ISSN={["1520-5835"]}, DOI={10.1021/ma061155f}, abstractNote={We use Monte Carlo computer simulation to study the effect of several molecular parameters on controlled/“living” radical polymerization in bulk and on flat substrates. Specifically, we investigate how the molecular weight and molecular weight distribution of grown polymers depend on the initial number of initiators, the initial number of monomers, the initiator activation probability, the initial probability of addition of a new monomer to a growing chain, the probability of terminating two “living” polymers, and the numbers of “living” polymers and their lifetime. Some observations reported here are common to both bulk- and surface-initiated polymerizations. Specifically, we demonstrate that increasing the termination probability and/or decreasing the initial probability of addition of a new monomer to a growing chain broadens the molecular weight distribution. In addition, decreasing the lifetime of the “living” radicals results in polymers with narrower molecular weight distributions. One of the goals...}, number={20}, journal={MACROMOLECULES}, author={Genzer, Jan}, year={2006}, month={Oct}, pages={7157–7169} }
 @article{clare_efimenko_fischer_genzer_abbott_2006, title={Orientations of liquid crystals in contact with surfaces that present continuous gradients of chemical functionality}, volume={18}, ISSN={["1520-5002"]}, DOI={10.1021/cm052537n}, abstractNote={We report the formation of continuous spatial gradients in the density of grafted semifluorinated chains on silicon oxide surfaces by vapor-phase diffusion of semifluorinated silanes. We quantify the orientations of the nematic liquid crystal (LC) 4-cyano-4‘-pentylbiphenyl on these surfaces as a function of local surface composition obtained by using NEXAFS. These measurements demonstrate that it is possible to obtain the full range of tilt angles of a LC on these surfaces. We also use the data provided by these gradient surfaces to test hypotheses regarding the nature of the interaction between the LC and surfaces that give rise to the range of tilted orientations of the LC. We conclude that the orientations of the LC are not determined solely by the density of grafted semifluorinated chains or by the density of residual hydroxyl groups presented at these surfaces following reactions with the silanes. Instead, our results raise the possibility that the tilt angles of the semifluorinated chains on these s...}, number={9}, journal={CHEMISTRY OF MATERIALS}, author={Clare, BH and Efimenko, K and Fischer, DA and Genzer, J and Abbott, NL}, year={2006}, month={May}, pages={2357–2363} }
 @misc{genzer_efimenko_2006, title={Recent developments in superhydrophobic surfaces and their relevance to marine fouling: a review}, volume={22}, ISSN={["1029-2454"]}, DOI={10.1080/08927010600980223}, abstractNote={Abstract In this review, a brief synopsis of superhydrophobicity (i.e. extreme non-wettability) and its implications on marine fouling are presented. A short overview of wettability and recent experimental developments aimed at fabricating superhydrophobic surfaces by tailoring their chemical nature and physical appearance (i.e. substratum texture) are reviewed. The formation of responsive/“smart” surfaces, which adjust their physico-chemical properties to variations in some outside physical stimulus, including light, temperature, electric field, or solvent, is also described. Finally, implications of tailoring the surface chemistry, texture, and responsiveness of surfaces on the design of effective marine fouling coatings are considered and discussed.}, number={5}, journal={BIOFOULING}, author={Genzer, Jan and Efimenko, Kirill}, year={2006}, pages={339–360} }
 @article{jhon_bhat_jeong_rojas_szleifer_genzer_2006, title={Salt-induced depression of lower critical solution temperature in a surface-grafted neutral thermoresponsive polymer}, volume={27}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200600031}, abstractNote={AbstractSummary: Quartz crystal microbalance with dissipation monitoring (QCM‐D) is employed to determine the effect of salt on the volume phase transition of thermoresponsive polymer brushes. Changes in mass and viscoelasticity of poly(N‐isopropylacrylamide) (PNIPAM) layers grafted from a QCM‐D crystal are measured as a function of temperature, upon contact with aqueous solutions of varying salt concentrations. The phase‐transition temperature of PNIPAM brushes, TC,graft, quantified from the QCM‐D measurements is found to decrease as the concentration of salt is increased. This phenomenon is explained by the tendency of salt ions to affect the structure of water molecules (Hofmeister effect). However, in contrast to the linear decrease in phase‐transition temperature upon increasing salt concentration observed for free PNIPAM, the trend in TC,graft for PNIPAM brushes is distinctively non‐linear.Schematic representation of the effect of salt concentration on the phase transition behavior of thermoresponsive polymer brushes.magnified imageSchematic representation of the effect of salt concentration on the phase transition behavior of thermoresponsive polymer brushes.
}, number={9}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Jhon, Young K. and Bhat, Rajendra R. and Jeong, Changwoo and Rojas, Orlando J. and Szleifer, Igal and Genzer, Jan}, year={2006}, month={May}, pages={697–701} }
 @misc{genzer_groenewold_2006, title={Soft matter with hard skin: From skin wrinkles to templating and material characterization}, volume={2}, ISSN={["1744-6848"]}, DOI={10.1039/b516741h}, abstractNote={The English-language dictionary defines wrinkles as "small furrows, ridges, or creases on a normally smooth surface, caused by crumpling, folding, or shrinking". In this paper we review the scientific aspects of wrinkling and the related phenomenon of buckling. Specifically, we discuss how and why wrinkles/buckles form in various materials. We also describe several examples from everyday life, which demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales. We will emphasize that wrinkling is not always a frustrating feature (, wrinkles in human skin), as it can help to assemble new structures, understand important physical phenomena, and even assist in characterizing chief material properties.}, number={4}, journal={SOFT MATTER}, author={Genzer, J and Groenewold, J}, year={2006}, month={Apr}, pages={310–323} }
 @article{tomlinson_efimenko_genzer_2006, title={Study of kinetics and macroinitiator efficiency in surface-initiated atom-transfer radical polymerization}, volume={39}, ISSN={["0024-9297"]}, DOI={10.1021/ma061885n}, abstractNote={Generation of surface-tethered block copolymer brushes with well-defined physicochemical characteristics requires achieving good control over the degree of polymerization of each block of the copolymer. In order to precisely form these block copolymer layers, one must (1) utilize a polymerization scheme that is capable of generating nearly monodisperse polymers, (2) fully characterize the kinetics of surface-initiated polymerization, and (3) produce macroinitiators with living characteristics capable of reinitiating the growth of each subsequent block. In this work, we describe technological steps leading to the controlled growth of surface-tethered homopolymers and multiblock copolymers via surface-initiated atom transfer radical polymerization (ATRP) from flat substrates. We first report on investigating the ability of a macroinitiator to reinitiate a homopolymer brush. We use computer simulations to illustrate the advantages of an “added deactivator” type ATRP over the traditional “sacrificial initiato...}, number={26}, journal={MACROMOLECULES}, author={Tomlinson, Michael R. and Efimenko, Kirill and Genzer, Jan}, year={2006}, month={Dec}, pages={9049–9056} }
 @article{smith_efimenko_fischer_lappi_kilpatrick_genzer_2007, title={Study of the packing density and molecular orientation of bimolecular self-assembled monolayers of aromatic and aliphatic organosilanes on silica}, volume={23}, ISSN={["0743-7463"]}, DOI={10.1021/la062475v}, abstractNote={Bimolecular self-assembled monolayers (SAMs) of aromatic and aliphatic chlorosilanes were self-assembled onto silica, and their characteristics were established by contact angle measurement, near-edge X-ray absorption fine structure spectroscopy, and Fourier transform infrared spectroscopy. Three aromatic constituents (phenyltrichlorosilane, benzyltrichlorosilane, and phenethyltrichlorosilane) were studied in combination with four aliphatic coadsorbates (butyltrichlorosilane, butyldimethylchlorosilane, octadecyltrichlorosilane, and octadecyldimethylchlorosilane). Our results demonstrate that whereas SAMs made of trichlorinated organosilanes are densely packed, SAMs prepared from monochlorinated species are less dense and poorly ordered. In mixed systems, trichlorinated aromatics and trichlorinated aliphatics formed SAMs with highly tunable compositions; their surfaces were compositionally homogeneous with no large-scale domain separation. The homogeneous nature of the resulting SAM was a consequence of the formation of in-plane siloxane linkages among neighboring molecules. In contrast, when mixing monochlorinated aliphatics with trichlorinated aromatics, molecular segregation occurred. Although the two shortest aromatic species did not display significant changes in orientation upon mixing with aliphatics, the aromatic species with the longest polymethylene spacer, phenethyltrichlorosilane, displayed markedly different orientation behavior in mixtures of short- and long-chain aliphatics.}, number={2}, journal={LANGMUIR}, author={Smith, Matthew B. and Efimenko, Kirill and Fischer, Daniel A. and Lappi, Simon E. and Kilpatrick, Peter K. and Genzer, Jan}, year={2007}, month={Jan}, pages={673–683} }
 @article{bhat_tomlinson_wu_genzer_2006, title={Surface-grafted polymer gradients: Formation, characterization, and applications}, volume={198}, ISBN={["3-540-30251-4"]}, ISSN={["1436-5030"]}, DOI={10.1007/12_060}, journal={SURFACE- INITIATED POLYMERIZATION II}, publisher={Berlin; New York: Springer}, author={Bhat, Rajendra R. and Tomlinson, Michael R. and Wu, Tao and Genzer, Jan}, year={2006}, pages={51–124} }
 @article{wei_lam_braunfeld_agard_genzer_spontak_2006, title={Tunable instability mechanisms of polymer thin films by molecular self-assembly}, volume={22}, ISSN={["0743-7463"]}, DOI={10.1021/la061391j}, abstractNote={Incorporation of a block copolymer into a thin polymer film is observed to alter both the rate and mechanism by which the film dewets from an immiscible polymer substrate. Films with little or no copolymer dewet by classical nucleation and growth of circular holes, and the dewetting rate decreases with increasing copolymer concentration. Increasing the copolymer content at constant film thickness generates copolymer micelles that adsorb/aggregate along the polymer/polymer interface and promote nonclassical dewetting fluctuations similar in appearance to spinodal dewetting. At higher copolymer concentrations, dewetting proceeds after a lengthy induction period by the nucleation and growth of flower-shaped holes suggestive of film pinning or viscous fingering. Atomic force microscopy of the polymer/polymer interface after removal of the top film by selective dissolution reveals substantial structural development due to copolymer self-assembly.}, number={21}, journal={LANGMUIR}, author={Wei, Bin and Lam, Peter G. and Braunfeld, Michael B. and Agard, David A. and Genzer, Jan and Spontak, Richard J.}, year={2006}, month={Oct}, pages={8642–8645} }
 @article{bhat_genzer_2007, title={Tuning the number density of nanoparticles by multivariant tailoring of attachment points on flat substrates}, volume={18}, ISSN={["0957-4484"]}, DOI={10.1088/0957-4484/18/2/025301}, abstractNote={We report on the organization of nanoparticles on a flat surface when there is strong yet tunable interaction between the particles and the surface. Specifically, we tailor the number density of citrate-stabilized gold nanoparticles on flat substrates by varying the concentration of the grafted amino groups on the surfaces and their degree of ionization. While the former effect is accomplished by decorating silica-based substrates with a molecular gradient of (3-aminopropyl)triethoxysilane (APTES), the latter effect is achieved by varying the degree of ionization of the −NH2 groups in APTES by varying the pH of the gold sol. We show that the measurement of particle number density on an APTES concentration gradient substrate at different pH values provides a simple, non-spectroscopic means to deduce the relative molecular concentration profile of APTES on the substrate.}, number={2}, journal={NANOTECHNOLOGY}, author={Bhat, Rajendra R. and Genzer, Jan}, year={2007}, month={Jan} }
 @article{striolo_jayaraman_genzer_hall_2005, title={Adsorption of comb copolymers on weakly attractive solid surfaces}, volume={123}, ISSN={["1089-7690"]}, DOI={10.1063/1.1993557}, abstractNote={In this work continuum and lattice Monte Carlo simulation methods are used to study the adsorption of linear and comb polymers on flat surfaces. Selected polymer segments, located at the tips of the side chains in comb polymers or equally spaced along the linear polymers, are attracted to each other and to the surface via square-well potentials. The rest of the polymer segments are modeled as tangent hard spheres in the continuum model and as self-avoiding random walks in the lattice model. Results are presented in terms of segment-density profiles, distribution functions, and radii of gyration of the adsorbed polymers. At infinite dilution the presence of short side chains promotes the adsorption of polymers favoring both a decrease in the depletion-layer thickness and a spreading of the polymer molecule on the surface. The presence of long side chains favors the adsorption of polymers on the surface, but does not permit the spreading of the polymers. At finite concentration linear polymers and comb polymers with long side chains readily adsorb on the solid surface, while comb polymers with short side chains are unlikely to adsorb. The simple models of comb copolymers with short side chains used here show properties similar to those of associating polymers and of globular proteins in aqueous solutions, and can be used as a first approximation to investigate the mechanism of adsorption of proteins onto hydrophobic surfaces.}, number={6}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Striolo, A and Jayaraman, A and Genzer, J and Hall, CK}, year={2005}, month={Aug} }
 @article{bhat_genzer_2006, title={Combinatorial study of nanoparticle dispersion in surface-grafted macromolecular gradients}, volume={252}, ISSN={["0169-4332"]}, DOI={10.1016/j.apsusc.2005.03.237}, abstractNote={Surface-tethered assemblies of polymers with gradually varying molecular weight (MW) and/or grafting density are utilized to control the dispersion of nanosized particles. Using several case studies we show that these gradient polymer specimens represent ideal systems for combinatorial exploration of the parameters that control the distribution of the particles in surface-grafted layers. We demonstrate that the particle distribution is governed by the interplay between the particle size and the grafting density and molecular weight of the polymer brush.}, number={7}, journal={APPLIED SURFACE SCIENCE}, author={Bhat, RR and Genzer, J}, year={2006}, month={Jan}, pages={2549–2554} }
 @article{schultz_hall_genzer_2005, title={Computer simulation of block copolymer/nanoparticle composites}, volume={38}, ISSN={["1520-5835"]}, DOI={10.1021/ma0496910}, abstractNote={Discontinuous molecular dynamics simulation is used to study the phase behavior of diblock copolymer/nanoparticle composites. The copolymers are modeled as chains of tangent hard-spheres with square shoulder repulsions between unlike species, while the nanoparticles are modeled as hard-spheres with a square shoulder repulsion with one of the copolymer blocks. The resulting phase diagrams are presented for composites containing nanoparticles of various sizes and interaction strengths and include lamellae, perforated lamellae, cylinders, and disordered phases. Composites containing large nanoparticles also exhibit two-phase coexistence between different copolymer phases or between a copolymer phase and a nanoparticle phase, depending on the nanoparticle interaction strength. We also present concentration profiles perpendicular to the lamellar interface for nanoparticles of different sizes and interaction strengths. Neutral nanoparticles concentrate at the interface between copolymer domains, while interacti...}, number={7}, journal={MACROMOLECULES}, author={Schultz, AJ and Hall, CK and Genzer, J}, year={2005}, month={Apr}, pages={3007–3016} }
 @article{jayaraman_hall_genzer_2005, title={Computer simulation study of pattern transfer in AB diblock copolymer film adsorbed on a heterogeneous surface}, volume={123}, ISSN={["1089-7690"]}, DOI={10.1063/1.2043048}, abstractNote={In this work we investigate how a pattern imposed in a copolymer film at a certain distance from the surface propagates through the film onto an adsorbing heterogeneous surface. We bias the copolymer film to adopt a specified target pattern and then use simulation to design a surface pattern that helps the adsorbed film to maintain that target pattern. We examine the effect of varying the copolymer chain length, the size of the target pattern, and the distance from the surface where the target pattern is applied, z′, on the extent of pattern transfer. For each chain length, target pattern, and z′ we compare the energy of the system when a pattern is applied in the bulk to the energy when no pattern is applied in order to understand why a certain pattern size is transferred to the surface with higher fidelity than the others. At constant chain length, pattern transfer is best when the pattern size brings the energy of the system close to the energy when no pattern is applied. At constant pattern size, pattern transfer is best in the systems with longer chains. This is because longer chains are more likely to adsorb as brushes and loops which then helps transfer the pattern through the adsorbed film down to the surface.}, number={12}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Jayaraman, A and Hall, CK and Genzer, J}, year={2005}, month={Sep} }
 @article{crowe_genzer_2005, title={Creating responsive surfaces with tailored wettability switching kinetics and reconstruction reversibility}, volume={127}, ISSN={["0002-7863"]}, DOI={10.1021/ja056926u}, abstractNote={We report on the formation of responsive surfaces with tailorable surface reconstruction kinetics and switching hysteresis by thiolene radical addition of mercaptoalkanols with variable lengths to poly(vinylmethylsiloxane) networks. Exposing these elastomer surfaces to water results in rearrangement of the hydrophilic alkanes at the surface. The rearrangement kinetics decreases with increasing number of the methylene spacers (n) in the mercaptoalkanol. The response kinetics is found to be very fast for n = 2 and 6. For instance, upon exposing to water, the water contact angle on 3-mercaptopropanol-based surfaces decreases by approximately 35 degrees at the rate of 2 degrees /s. The high flexibility of the siloxane backbone endows these materials with switching longevity; the materials were able to switch their wettability over 10 cycles with minimum hysteresis. Increasing the number of methylene spacers to n = 11 decreases the surface reorganization dramatically. Formation of semicrystalline regions in such materials (detected via IR) is responsible for initial "sluggish" kinetics and eventual surface "freezing".}, number={50}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Crowe, JA and Genzer, J}, year={2005}, month={Dec}, pages={17610–17611} }
 @article{jayaraman_hall_genzer_2005, title={Designing pattern-recognition surfaces for selective adsorption of copolymer sequences using lattice Monte Carlo simulation}, volume={94}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.94.078103}, abstractNote={We describe a simulation method to design surfaces for recognizing specific monomer sequences in copolymers. We fix the monomer sequence statistics of the AB copolymers on a surface containing two types of sites and allow the simulation to iterate towards an optimal surface pattern that can recognize and selectively adsorb the sequence in the copolymer. During the simulation the surface pattern is designed by switching identities of two randomly picked sites. For copolymers with less blocky sequences the designed surfaces recognize the correct sequence well when the segment-surface interactions dominate over the intersegment interactions. For copolymers with more blocky sequences recognition is good when the segment-surface interactions are only slightly stronger than the intersegment interactions.}, number={7}, journal={PHYSICAL REVIEW LETTERS}, author={Jayaraman, A and Hall, CK and Genzer, J}, year={2005}, month={Feb} }
 @article{tomlinson_genzer_2005, title={Evolution of surface morphologies in multivariant assemblies of surface-tethered diblock copolymers after selective solvent treatment}, volume={21}, ISSN={["0743-7463"]}, DOI={10.1021/la051523t}, abstractNote={We study systematically the topography behavior of PHEMA-b-PMMA block as a function of the PHEMA and PMMA block lengths after selectively collapsing the top (PMMA) block by using surface-anchored assemblies of poly(2-hydroxyethyl methacrylate-b-methyl methacrylate), PHEMA-b-PMMA, block copolymer with orthogonally varying lengths of each block. Our experimental results are in excellent qualitative agreement with topology diagrams predicted by self-consistent field calculations of Zhulina and co-workers.}, number={25}, journal={LANGMUIR}, author={Tomlinson, MR and Genzer, J}, year={2005}, month={Dec}, pages={11552–11555} }
 @article{bhat_chaney_rowley_liebmann-vinson_genzer_2005, title={Inside Front Cover: Tailoring Cell Adhesion Using Surface-Grafted Polymer Gradient Assemblies (Adv. Mater. 23/2005)}, volume={17}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.200590122}, DOI={10.1002/adma.200590122}, abstractNote={AbstractA three‐step approach to tailor cell adhesion via surface‐grafted polymer gradients is shown in this image from the work of Genzer and co‐workers on p. 2802. Surface‐anchored polymer assemblies with gradients in polymer molecular weight and/or grafting density are first employed to tailor adsorption of the protein, which in turn governs the number density as well as the extent of spreading of osteoblastic cells. Increasing the surface coverage of the polymer results in a decrease in the amount of protein adsorbed, which causes a decrease in the number of cells adhered and a change in cell morphology.}, number={23}, journal={Advanced Materials}, publisher={Wiley}, author={Bhat, R. R. and Chaney, B. N. and Rowley, J. and Liebmann-Vinson, A. and Genzer, J.}, year={2005}, month={Dec}, pages={NA-NA} }
 @article{efimenko_rackaitis_manias_vaziri_mahadevan_genzer_2005, title={Nested self-similar wrinkling patterns in skins}, volume={4}, ISSN={["1476-4660"]}, DOI={10.1038/nmat1342}, abstractNote={Stiff thin films on soft substrates are both ancient and commonplace in nature; for instance, animal skin comprises a stiff epidermis attached to a soft dermis. Although more recent and rare, artificial skins are increasingly used in a broad range of applications, including flexible electronics, tunable diffraction gratings, force spectroscopy in cells, modern metrology methods, and other devices. Here we show that model elastomeric artificial skins wrinkle in a hierarchical pattern consisting of self-similar buckles extending over five orders of magnitude in length scale, ranging from a few nanometres to a few millimetres. We provide a mechanism for the formation of this hierarchical wrinkling pattern, and quantify our experimental findings with both computations and a simple scaling theory. This allows us to harness the substrates for applications. In particular, we show how to use the multigeneration-wrinkled substrate for separating particles based on their size, while simultaneously forming linear chains of monodisperse particles.}, number={4}, journal={NATURE MATERIALS}, author={Efimenko, K and Rackaitis, M and Manias, E and Vaziri, A and Mahadevan, L and Genzer, J}, year={2005}, month={Apr}, pages={293–297} }
 @article{carla_wang_hussain_efimenko_genzer_grant_sarti_carbonell_doghieri_2005, title={Nonequilibrium model for sorption and swelling of bulk glassy polymer films with Supercritical carbon dioxide}, volume={38}, ISSN={["1520-5835"]}, DOI={10.1021/ma0506684}, abstractNote={A new procedure is introduced for the calculation of solubility isotherms of plasticizing agents in glassy polymer matrices with particular application to the case of absorption of supercritical gases in bulk glassy polymer films. The model presented is an extension of the nonequilibrium thermodynamics for glassy polymers (NET-GP) approach, modified to allow for the calculation of the effects of pressure, temperature, and gas concentration on the glass transition. Mass sorption and one- dimensional swelling behavior are analyzed for the carbon dioxide (CO2)-poly(methyl methacrylate) (PMMA) system at high pressure. A quantitative comparison is presented between the model performance and experimental data measured using quartz crystal microbalance (QCM) and high-pressure ellipsometry (HPE).}, number={24}, journal={MACROMOLECULES}, author={Carla, V and Wang, K and Hussain, Y and Efimenko, K and Genzer, J and Grant, C and Sarti, GC and Carbonell, RG and Doghieri, F}, year={2005}, month={Nov}, pages={10299–10313} }
 @article{bhat_tomlinson_genzer_2005, title={Orthogonal surface-grafted polymer gradients: A versatile combinatorial platform}, volume={43}, ISSN={["1099-0488"]}, DOI={10.1002/polb.20640}, abstractNote={AbstractOrthogonal polymer brush gradients are assemblies of surface‐anchored macromolecules, in which two material properties of the grafted chains (e.g., grafting density, molecular weight) vary independently in orthogonal directions. Here, we describe the formation and applications of two such orthogonal assemblies, involving: (1) molecular weight and grafting density (MW/σ) gradients of a given polymer and (2) molecular weight gradients (MW1/MW2), of two different polymers. Each point on orthogonal gradient substrate represents a unique combination of the two surface properties being varied, thus facilitating systematic investigation of a phenomenon that depends on the two said properties. We illustrate this point by employing orthogonal structures to study systematically: (1) formation of polymer brush‐nanoparticle composite assemblies, (2) protein adsorption and cell adhesion, and (3) chain conformations in tethered diblock copolymers exposed to selective solvents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3384–3394, 2005}, number={23}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Bhat, RR and Tomlinson, MR and Genzer, J}, year={2005}, month={Dec}, pages={3384–3394} }
 @article{efimenko_crowe_manias_schwark_fischer_genzer_2005, title={Rapid formation of soft hydrophilic silicone elastomer surfaces}, volume={46}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2005.07.046}, abstractNote={We report on the rapid formation of hydrophilic silicone elastomer surfaces by ultraviolet/ozone (UVO) irradiation of poly(vinylmethyl siloxane) (PVMS) network films. Our results reveal that the PVMS network surfaces render hydrophilic upon only a short UVO exposure time (seconds to a few minutes). We also provide evidence that the brief UVO irradiation treatment does not cause dramatic changes in the surface modulus of the PVMS network. We compare the rate of formation of hydrophilic silicone elastomer surfaces made of PVMS to those of model poly(dimethyl siloxane) (PDMS) and commercial-grade PDMS (Sylgard-184). We find that relative to PVMS, 20 times longer UVO treatment times are needed to oxidize the PDMS network surfaces in order to achieve a comparable density of surface-bound hydrophilic moieties. The longer UVO treatment times for PDMS are in turn responsible for the dramatic increase in surface modulus of UVO treated PDMS, relative to PVMS. We also study the formation of self-assembled monolayers (SAMs) made of semifluorinated organosilane precursors on the PVMS-UVO and PDMS-UVO network surfaces. By tuning the UVO treatment times and by utilizing mono- and tri-functional organosilanes we find that while mono-functionalized organosilanes attach directly to the substrate, SAMs of tri-functionalized organosilanes form in-plane networks on the underlying UVO-modified silicone elastomer surface, even with only short UVO exposure times.}, number={22}, journal={POLYMER}, author={Efimenko, K and Crowe, JA and Manias, E and Schwark, DW and Fischer, DA and Genzer, J}, year={2005}, month={Oct}, pages={9329–9341} }
 @article{bhat_chaney_rowley_liebmann-vinson_genzer_2005, title={Tailoring cell adhesion using surface-grafted polymer gradient assemblies}, volume={17}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200500858}, abstractNote={higher-energy emissions due to impurity phases. In conclusion, well-defined [ZnSe](DETA)0.5 nanobelts have been synthesized successfully by tuning the composition of a ternary solution made of DETA, hydrazine hydrate, and deionized water. We find that an appropriate amount of hydrazine hydrate is essential for the formation of elegant [ZnSe](DETA)0.5 nanobelts. While the optical properties of the nanobelts are not changed significantly, the ability to make these II–VI-based hybrid semiconductor nanostructure microparticles into nanocrystals with uniform shape and size is one step further towards the miniaturization of devices. In addition, surface modification or combination with other materials may introduce new phenomena and properties into this system with remarkable quantum size effects and expand their potential for applications in advanced semiconductor devices.}, number={23}, journal={ADVANCED MATERIALS}, author={Bhat, RR and Chaney, BN and Rowley, J and Liebmann-Vinson, A and Genzer, J}, year={2005}, month={Dec}, pages={2802-+} }
 @article{genzer_2005, title={Templating surfaces with gradient assemblies}, volume={81}, ISSN={["1545-5823"]}, DOI={10.1080/00218460590944855}, abstractNote={ABSTRACT One of the most versatile and widely used methods of forming surfaces with position-dependent wettability is that conceived by Chaudhury and Whitesides more than a decade ago [Science 256, 1539 (1992)]. In this paper we review several projects that utilize this gradient-forming methodology for: controlled of deposition of self-assembled monolayers on surfaces, generating arrays of nanoparticles with number density gradients, probing the mushroom-to-brush transition in surface-anchored polymers, and controlling the speed of moving liquid droplets on surfaces. *This paper is dedicated to Professor Manoj K. Chaudhury for his contributions to the field of self-assembly and surface chemistry. The author is grateful for countless fruitful discussions he has had with Professor Chaudhury over the past several years, his friendship, encouragement, and overwhelming support. The author wants to acknowledge all past and current post-doctoral and doctoral students from his group who have contributed to the various projects outlined in this paper: Dr. Kirill Efimenko, Dr. Tao Wu, Rajendra R. Bhat, Michael R. Tomlinson, Tiffani N. Bailey, and Randal J. Petrie. The author also thanks Dr. Daniel A. Fischer (NIST) and Professor Christopher S. Gorman (NCSU) for their collaboration during the various stages of the research described in this paper. We are grateful to the National Science Foundation, The Camille & Henry Dreyfus Foundation, and 3M for their generous financial support. NEXAFS spectroscopy experiments were carried out at the National Synchrotron Light Source, Brookhaven National Laboratory, which is supported by the U. S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences.}, number={3-4}, journal={JOURNAL OF ADHESION}, author={Genzer, J}, year={2005}, pages={417–435} }
 @article{bhat_genzer_2005, title={Using spectroscopic ellipsometry for quick prediction of number density of nanoparticles bound to non-transparent solid surfaces}, volume={596}, ISSN={["1879-2758"]}, DOI={10.1016/j.susc.2005.09.014}, abstractNote={We report on the use of spectroscopic ellipsometry (SE) in predicting number density of nanoparticles bound to the surfaces decorated with either organic monolayers or surface-grafted polymers. Two systems are considered that comprise citrate-stabilized gold nanoparticles adsorbed on: (1) 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer (SAM), and (2) surface-tethered polyacrylamide (PAAm). Number density of gold nanoparticles on the surface is varied systematically by gradually increasing either the concentration of APTES molecules in the SAM or molecular weight of grafted PAAm. The adsorption of gold nanoparticles on APTES gradient surfaces is monitored via atomic force microscopy (AFM), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and SE. The partition of gold nanoparticles on PAAm gradient assemblies is characterized by AFM, ultraviolet–visible (UV–vis) spectroscopy, and SE. By correlating the results obtained from the various techniques on nanoparticle coatings, we derive an empirical linear relationship between the number density of nanoparticles on surfaces and cos (Δ) parameter measured in SE. Excellent agreement between nanoparticle number density determined experimentally from AFM scans and that predicted by SE proves the potential of SE as a quick, predictive technique to estimate number density of nanoparticles bound to solid, non-transparent substrates.}, number={1-3}, journal={SURFACE SCIENCE}, author={Bhat, RR and Genzer, J}, year={2005}, month={Dec}, pages={187–196} }
 @article{schultz_hall_genzer_2004, title={Box length search algorithm for molecular simulation of systems containing periodic structures}, volume={120}, ISSN={["1089-7690"]}, DOI={10.1063/1.1636156}, abstractNote={We have developed a box length search algorithm to efficiently find the appropriate box dimensions for constant-volume molecular simulation of periodic structures. The algorithm works by finding the box lengths that equalize the pressure in each direction while maintaining constant total volume. Maintaining the volume at a fixed value ensures that quantitative comparisons can be made between simulation and experimental, theoretical or other simulation results for systems that are incompressible or nearly incompressible. We test the algorithm on a system of phase-separated block copolymers that has a preferred box length in one dimension. We also describe and test a Monte Carlo algorithm that allows the box lengths to change while maintaining constant volume. We find that the box length search algorithm converges at least two orders of magnitude more quickly than the variable box length Monte Carlo method. Although the box length search algorithm is not ergodic, it successfully finds the box length that minimizes the free energy of the system. We verify this by examining the free energy as determined by the Monte Carlo simulation.}, number={4}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Schultz, AJ and Hall, CK and Genzer, J}, year={2004}, month={Jan}, pages={2049–2055} }
 @article{semler_genzer_2004, title={Cover Picture: Macromol. Theory Simul. 3/2004}, volume={13}, ISSN={1022-1344 1521-3919}, url={http://dx.doi.org/10.1002/mats.200490004}, DOI={10.1002/mats.200490004}, abstractNote={Cover: The picture on the cover represents Monte Carlo simulation generated conformations of copolymers with alternating and diblock sequences on chemically patterned substrates with strong and week attractions between the surface active sites and the adsorbing monomers along the copolymer backbone.Further details can be found in the Full Paper by J. J. Semler and J. Genzer* on page 219.}, number={3}, journal={Macromolecular Theory and Simulations}, publisher={Wiley}, author={Semler, James J. and Genzer, Jan}, year={2004}, month={Apr}, pages={193–193} }
 @article{wei_genzer_spontak_2004, title={Dewetting behavior of a block copolymer/homopolymer thin film on an immiscible homopolymer substrate}, volume={20}, ISSN={["0743-7463"]}, DOI={10.1021/la049562c}, abstractNote={Numerous previous studies have established that the addition of a microphase-ordered AB diblock copolymer to a thin homopolymer A (hA) film can slow, if not altogether prevent, film rupture and subsequent film dewetting on a hard substrate such as silica. However, only a few reports have examined comparable phenomena when the hA/AB blend resides on a soft B-selective surface, such as homopolymer B (hB). In this work, the dewetting kinetics of thin films composed of polystyrene (PS) and a symmetric poly(styrene-b-methyl methacrylate) (SM) diblock copolymer on a poly(methyl methacrylate) substrate is investigated by hot-stage light microscopy. Without the SM copolymer, the dewetting rate of the PS layer is constant under isothermal conditions and exhibits Arrhenius behavior with an apparent activation energy of approximately 180 kJ/mol. Addition of the copolymer promotes a crossover from early- to late-stage dewetting kinetics, as evidenced by measurably different dewetting rates. Transmission electron microscopy reveals the morphological characteristics of dewetted PS/SM films as functions of film thickness and SM concentration.}, number={20}, journal={LANGMUIR}, author={Wei, B and Genzer, J and Spontak, RJ}, year={2004}, month={Sep}, pages={8659–8667} }
 @article{wei_gurr_genzer_qiao_solomon_spontak_2004, title={Dewetting of star nanogel/homopolymer blends from an immiscible homopolymer substrate}, volume={37}, ISSN={["0024-9297"]}, DOI={10.1021/ma048636o}, abstractNote={Departments of Chemical & BiomolecularEngineering and Materials Science & Engineering,North Carolina State University,Raleigh, North Carolina 27695, and Polymer Science Group,Department of Chemical & Biomolecular Engineering,University of Melbourne, Victoria 3010, AustraliaReceived July 6, 2004Revised Manuscript Received August 26, 2004}, number={21}, journal={MACROMOLECULES}, author={Wei, B and Gurr, PA and Genzer, J and Qiao, GG and Solomon, DH and Spontak, RJ}, year={2004}, month={Oct}, pages={7857–7860} }
 @article{petrie_bailey_gorman_genzer_2004, title={Fast directed motion of "Fakir" droplets}, volume={20}, ISSN={["0743-7463"]}, DOI={10.1021/la048612a}, abstractNote={In this Letter, we report on the motion of water droplets on surfaces decorated with molecular gradients comprising semifluorinated (SF) organosilanes. SF molecular gradients deposited on flat silica substrates facilitate faster motion of water droplets relative to the specimens covered with an analogous hydrocarbon gradient. Further increase in the drop speed is achieved by advancing it along porous substrates coated with the SF wettability gradients. The results of our experiments are in quantitative agreement with a simple scaling theory that describes the faster liquid motion in terms of reduced friction at the liquid/substrate interface.}, number={23}, journal={LANGMUIR}, author={Petrie, RJ and Bailey, T and Gorman, CB and Genzer, J}, year={2004}, month={Nov}, pages={9893–9896} }
 @misc{genzer_efimenko_2004, title={Methods for forming tunable molecular gradients on substrates}, volume={6,770,323}, number={2004 Aug. 03}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Genzer, J. and Efimenko, K.}, year={2004} }
 @article{semler_tonelli_beevers_genzer_2004, title={Monomer sequence mediated mobility in random copolymers under confinement}, volume={3}, journal={Nature Materials}, author={Semler, J. J. and Tonelli, A. E. and Beevers, M. and Genzer, J.}, year={2004} }
 @article{semler_genzer_2004, title={Monte Carlo simulations of copolymer adsorption at planar chemically patterned surfaces: Effect of interfacial interaction}, volume={13}, ISSN={["1521-3919"]}, DOI={10.1002/mats.200300039}, abstractNote={AbstractSummary: Monte Carlo simulation utilizing the bond fluctuation model in conjunction with single and configurational biased Monte Carlo moves is used to study the adsorption of diblock (A‐block‐B) and alternating (A‐alt‐B) copolymers at flat, chemically heterogeneous surfaces comprising C and D domains. The main objective of this work is to address the effect of the strength of attraction between the adsorbing surface domains, D, and the copolymer adsorbing segments, B, on the copolymer's ability to recognize the chemical pattern on the surface. The results of our simulations reveal that both block and alternating copolymers have the ability to recognize the surface motif and transcribe it into the bulk material. The extent to which diblock copolymers transfer the chemical pattern from the surface to the bulk is relatively unaffected when the attractive B‐D potential is increased beyond a certain critical value. This behavior stems from the brush‐like conformation adopted by the diblock copolymer at the substrate. In contrast to the diblock copolymer, the adsorption of the alternating copolymer is influenced by the strength of the attraction between the copolymer's adsorbing segments and the adsorbing domains on the surface. Since the B segments are distributed evenly along the backbone, the alternating copolymers are more likely to adopt conformations in which the whole chain is “zipped” to the surface. The resultant entropic frustration is then alleviated through an increased formation of loops with little change to their length. Such conformational changes endow the alternating copolymer with the ability to invert the substrate pattern as the distance away from the surface is increased.image}, number={3}, journal={MACROMOLECULAR THEORY AND SIMULATIONS}, author={Semler, JJ and Genzer, J}, year={2004}, month={Apr}, pages={219–229} }
 @article{seog_dean_rolauffs_wu_genzer_plaas_grodzinsky_ortiz_2005, title={Nanomechanics of opposing glycosaminoglycan macromolecules}, volume={38}, ISSN={["1873-2380"]}, DOI={10.1016/j.jbiomech.2004.09.010}, abstractNote={In this study, the net intermolecular interaction force between a chondroitin sulfate glycosaminoglycan (GAG)-functionalized probe tip and an opposing GAG-functionalized planar substrate was measured as a function of probe tip-substrate separation distance in aqueous electrolyte solutions using the technique of high resolution force spectroscopy. A range of GAG grafting densities as near as possible to native cartilage was used. A long-range repulsive force between GAGs on the probe tip and substrate was observed, which increased nonlinearly with decreasing separation distance between probe tip and substrate. Data obtained in 0.1 M NaCl was well predicted by a recently developed Poisson-Boltzmann-based theoretical model that describes normal electrostatic double layer interaction forces between two opposing surfaces of end-grafted, cylindrical rods of constant volume charge density and finite length, which interdigitate upon compression. Based on these results, the nanomechanical data and interdigitated rod model were used together to estimate the electrostatic component of the equilibrium modulus of cartilage tissue, which was then compared to that of normal adult human ankle cartilage measured in uniaxial confined compression.}, number={9}, journal={JOURNAL OF BIOMECHANICS}, author={Seog, J and Dean, D and Rolauffs, B and Wu, T and Genzer, J and Plaas, AHK and Grodzinsky, AJ and Ortiz, C}, year={2005}, month={Sep}, pages={1789–1797} }
 @article{fleming_ulrich_efimenko_genzer_chan_madey_oh_zhou_rowe_2004, title={Near-edge absorption fine structure and UV photoemission spectroscopy studies of aligned single-walled carbon nanotubes on Si(100) substrates}, volume={22}, ISSN={["2166-2746"]}, DOI={10.1116/1.1775190}, abstractNote={We report near-edge absorption fine structure (NEXAFS) and UV photoemission spectroscopy (UPS) studies of aligned single-walled carbon nanotube films on Si(100) substrates. Orientation of the films was detected in the NEXAFS spectra, with the intensity of the π* core exciton at 284.4 eV showing a strong dependence on nanotube alignment with respect to the polarization of the incident radiation. At lower angles of incidence, the intensity of the π* peak was higher for all orientations, which we attribute to the greater accessibility of the π* orbitals. UPS spectra of the films showed little angular dependence and included features consistent with the total density of states of graphite. As a result of the nanotube curvature and the distribution of nanotube chiralities, the UPS spectra are similar to angle-integrated graphite spectra.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Fleming, L and Ulrich, MD and Efimenko, K and Genzer, J and Chan, ASY and Madey, TE and Oh, SJ and Zhou, O and Rowe, JE}, year={2004}, pages={2000–2004} }
 @article{wu_tomlinson_efimenko_genzer_2003, title={A combinatorial approach to surface anchored polymers}, volume={38}, ISSN={["1573-4803"]}, DOI={10.1023/A:1027373216389}, number={22}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Wu, T and Tomlinson, M and Efimenko, K and Genzer, J}, year={2003}, month={Nov}, pages={4471–4477} }
 @article{wu_sambasivan_wang_wallace_genzer_fischer_2003, title={A direct comparison of surface and bulk chain-relaxation in polystyrene}, volume={12}, ISSN={["1292-8941"]}, DOI={10.1140/epje/i2003-10050-6}, abstractNote={Near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy was used to measure simultaneously the relaxation rates of polystyrene (PS) molecules at the free surface and in the bulk. The samples were uniaxially stretched and annealed at temperatures below the bulk glass transition temperature of PS. The surface and bulk chain relaxation was monitored by measuring the partial-electron and the fluorescence NEXAFS yields, respectively, both parallel and perpendicular to the stretching direction. The decay of the optical birefringence was also measured to provide an independent measure of the bulk relaxation. Relaxation of PS chains was found to occur faster on the surface relative to the bulk. The magnitude of the surface glass transition temperature suppression over the bulk was estimated based on the information on the temperature dependence of the rates.}, number={1}, journal={EUROPEAN PHYSICAL JOURNAL E}, author={Wu, WL and Sambasivan, S and Wang, CY and Wallace, WE and Genzer, J and Fischer, DA}, year={2003}, month={Sep}, pages={127–132} }
 @article{bhat_tomlinson_genzer_2004, title={Assembly of nanoparticles using surface-grafted orthogonal polymer gradients}, volume={25}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200300163}, abstractNote={AbstractSummary: We report on preparing poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) gradient substrate, wherein molecular weight (MW) and grafting density (σ) of the surface‐anchored PDMAEMA chains vary continuously in two orthogonal directions. Such a specimen is used to control the assembly of charged gold nanoparticles. Increasing MW and σ of the grafted PDMAEMA cause an enhanced binding of the nanoparticles to PDMAEMA, thus leading to an orthogonal number density gradient of surface‐bound gold nanoparticles.magnified image}, number={1}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Bhat, RR and Tomlinson, MR and Genzer, J}, year={2004}, month={Jan}, pages={270–274} }
 @article{genzer_fischer_efimenko_2003, title={Combinatorial near-edge x-ray absorption fine structure: Simultaneous determination of molecular orientation and bond concentration on chemically heterogeneous surfaces}, volume={82}, ISSN={["1077-3118"]}, DOI={10.1063/1.1535271}, abstractNote={We show that simultaneous molecular orientation and bond chemistry of planar chemically heterogeneous surfaces can be obtained by combining near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and rastering the incident x-ray beam on the specimen. This rastering produces serially two-dimensional NEXAFS images in space and energy, revealing information about the chemistry (including bond concentration) and orientation of the surface-bound molecules with submillimeter planar spatial resolution and submonolayer molecular sensitivity. We illustrate the power of the combinatorial NEXAFS method by simultaneously probing the concentration and molecular orientation of semifluorinated (SF) molecules in double-SF molecular gradients on flat silica substrates.}, number={2}, journal={APPLIED PHYSICS LETTERS}, author={Genzer, J and Fischer, DA and Efimenko, K}, year={2003}, month={Jan}, pages={266–268} }
 @article{bhat_genzer_chaney_sugg_liebmann-vinson_2003, title={Controlling the assembly of nanoparticles using surface grafted molecular and macromolecular gradients}, volume={14}, ISSN={["1361-6528"]}, DOI={10.1088/0957-4484/14/10/313}, abstractNote={We report on the generation of assemblies comprising number density gradients of nanoparticles in two (2D) and three (3D) dimensions. These structures are fabricated by creating a surface-bound organic template which directs the spatial arrangement of gold nanoparticles. The 2D template is made of amine-terminated organosilane with a concentration gradient along the solid substrate. The 3D matrix comprises surface-anchored poly(acryl amide), whose molecular weight changes gradually on the specimen. In both cases, the composite is assembled at low pH, where the positively charged –NH3+ groups within the organic scaffold attract negatively charged gold nanoparticles. We use a battery of experimental tools to determine the number density of particles along the gradient substrate and in the case of 3D structures also their spatial distribution. For 2D gradient assemblies, we show that gold nanoparticle coverage on the surface decreases gradually as the concentration of substrate-bound aminosilane decreases. The number of particles in the polymer brush/particle hybrid is found to increase with increasing polymer molecular weight. We show that for a given grafting density of polymer brush, larger particles predominantly stay near the brush–air interface. In contrast, smaller nanoparticles penetrate deeper into the polymer brush, thus forming a 3D structure. Finally, we discuss possible applications of these nanoparticle gradient assemblies.}, number={10}, journal={NANOTECHNOLOGY}, author={Bhat, RR and Genzer, J and Chaney, BN and Sugg, HW and Liebmann-Vinson, A}, year={2003}, month={Oct}, pages={1145–1152} }
 @article{genzer_fischer_efimenko_2003, title={Fabricating two-dimensional molecular gradients via asymmetric deformation of uniformly-coated elastomer sheets}, volume={15}, ISSN={["0935-9648"]}, DOI={10.1002/adma.200305151}, abstractNote={Molecular gradients comprising two‐dimensional in‐plane variation of density of substrate‐grafted molecules (see Figure, darker regions in the plot denote regions with higher substrate density) have been fabricated. This is achieved by utilizing the technology of “mechanically assembled monolayers” in conjunction with in‐plane asymmetric stretching of elastomeric substrates uniformly‐coated with organosilane precursors.}, number={18}, journal={ADVANCED MATERIALS}, author={Genzer, J and Fischer, DA and Efimenko, K}, year={2003}, month={Sep}, pages={1545-+} }
 @article{wu_efimenko_vlcek_subr_genzer_2003, title={Formation and properties of anchored polymers with a gradual variation of grafting densities on flat substrates}, volume={36}, ISSN={["1520-5835"]}, DOI={10.1021/ma0257189}, abstractNote={We show that assemblies comprising anchored polymers with a gradual variation of grafting densities on solid substrates can be generated by first covering the substrate with a molecular gradient of the polymerization initiator, followed by polymerization from the substrate-bound initiator centers (“grafting from”). We apply this technique to prepare grafting density gradients of poly(acrylamide) (PAAm) on flat silica substrates. We demonstrate that using the grafting density gradient geometry, the mushroom-to-brush transition can be accessed on a single sample. This transition is detected by monitoring the dependence of the thickness of the grafted PAAm in a good solvent using variable angle spectroscopic ellipsometry. Wettability experiments performed on the gradient PAAm substrate provide complementary information about the nature of the mushroom-to-brush transition.}, number={7}, journal={MACROMOLECULES}, author={Wu, T and Efimenko, K and Vlcek, P and Subr, V and Genzer, J}, year={2003}, month={Apr}, pages={2448–2453} }
 @article{tomlinson_genzer_2003, title={Formation of grafted macromolecular assemblies with a gradual variation of molecular weight on solid substrates}, volume={36}, ISSN={["1520-5835"]}, DOI={10.1021/ma025937u}, abstractNote={The development of new polymeric materials and structures relies primarily on controlled polymerizations, chain growth polymerizations that proceed without irreversible chain transfer, and chain termination. Recent advances in living radical polymerizations have led to the advancement of robust and simple polymerization methodologies. In particular, atom transfer radical polymerization (ATRP), pioneered by Sawamoto1 and Matyjaszewski,2 provides a convenient means of synthesizing end-functionalized and body-functionalized polymers, thereby enabling the synthesis of a variety of polymer architectures, including block copolymers, multiarmed stars, hyperbranched polymers, and polymer combs with well-defined composition and relatively low molecular weight polydispersities.3 Many types of monomers including acrylates, methacrylates, styrenes, vinylpyridines, acrylonitrile, and acrylamides have been polymerized successfully via ATRP. Continuous molecular gradients represent chief tools for combinatorial chemistry and materials science.4,5 These multivariant methods enable systematic variation of one or more physicochemical properties, thus enabling systematic exploration of the broad parameter space, improved efficiency, and lower cost.6 Surface-tethered polymer structures represent an effective means of tuning the physicochemical properties of substrates. Recently, techniques, involving the patterning of polymer layers grafted to the substrate, have been developed that utilize ATRP.7-14 The latter group of technologies is based on selectively decorating the material surfaces with polymerization initiators and then performing the polymerization directly on the surface (“grafting from”). In this Communication we report on creating surfacegrafted layers with a gradual variation of polymer molecular weight (or length). We use ATRP of methyl methacrylate (MMA) from water/methanol solution. Previous reports indicated that such polymerization proceeds rapidly even at a room temperature.11,15 Surface-bound macromolecular assemblies with position-dependent molecular weight were prepared in a custom-designed apparatus shown schematically in Figure 1. Silicon wafer (≈1 × 5 cm) was first covered with (11-(2-bromo-2-methyl)propionyloxy)undecyltri* Corresponding author: e-mail Jan_Genzer@ncsu.edu; Tel +1-919-515-2069. Figure 1. Schematic of the apparatus for creating surfacegrafted polymer assemblies with a gradient in molecular weight. The chamber is loaded with a solution comprising a monomer, bipyridine, CuCl2, and the solvent. The chamber is then purged with nitrogen in order to remove oxygen. CuCl is added, and the silicon wafer, covered with a chemisorbed ATRP initiator, is lowered into the solution. During the reaction, the micropump removes the solution from the chamber causing a steady decrease in the vertical position of the three-phase (substrate/solution/inert) contact line. The profile (including the “steepness”) of the polymer brush length gradient on the substrate can be controlled by varying the removal rate. Volume 36, Number 10 May 20, 2003}, number={10}, journal={MACROMOLECULES}, author={Tomlinson, MR and Genzer, J}, year={2003}, month={May}, pages={3449–3451} }
 @article{tomlinson_genzer_2003, title={Formation of surface-grafted copolymer brushes with continuous composition gradients}, ISSN={["1364-548X"]}, DOI={10.1039/b303823h}, abstractNote={We report on a simple methodology that facilitates the generation of surface-grafted assemblies comprising block copolymers with tunable composition and molecular weight gradients along flat solid substrates.}, number={12}, journal={CHEMICAL COMMUNICATIONS}, author={Tomlinson, MR and Genzer, J}, year={2003}, pages={1350–1351} }
 @article{fischer_efimenko_bhat_sambasivan_genzer_2004, title={Mapping surface chemistry and molecular orientation with combinatorial near-edge X-ray absorption fine structure spectroscopy}, volume={25}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200300178}, abstractNote={AbstractSummary: Mapping the bond chemistry and molecular orientation of self‐assembled monolayer gradients on flat surfaces and reaction intermediates in catalyst arrays is made possible using combinatorial near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy. These spatially resolved NEXAFS maps have been made by utilizing synchrotron‐based NEXAFS spectroscopy in conjunction with a computer controlled precision sample manipulator. The NEXAFS maps reveal bond concentration, rehybridization, and orientation of the surface‐bound molecules with sub‐millimeter planar spatial resolution and sub‐monolayer molecular sensitivity. The wide applicability of the combinatorial NEXAFS method is illustrated by mapping: (1) the concentration and molecular orientation of semifluorinated molecules in molecular gradients; (2) the concentration of amino groups in molecular gradients used for nanoparticle templating, and (3) the rehybridization of propylene intermediates on zeolite catalyst arrays used for measuring solid‐state acidity and catalyst activity.The principle of “combinatorial” NEXAFS. The molecular gradient is indicated pictorially by the shading on the specimen.magnified imageThe principle of “combinatorial” NEXAFS. The molecular gradient is indicated pictorially by the shading on the specimen.
}, number={1}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Fischer, DA and Efimenko, K and Bhat, RR and Sambasivan, S and Genzer, J}, year={2004}, month={Jan}, pages={141–149} }
 @article{semler_genzer_2003, title={Monte Carlo simulations of copolymer adsorption at planar chemically patterned surfaces: Effect of surface domain sizes}, volume={119}, ISSN={["0021-9606"]}, DOI={10.1063/1.1597872}, abstractNote={We present results of Monte Carlo simulation studies utilizing the bond fluctuation model in conjunction with single and configurational biased Monte Carlo moves to investigate the adsorption of diblock (A–b–B) and alternating (A–alt–B) copolymers at physically flat surfaces made of an equal number of two chemically different sites, C and D. The adsorption of the copolymer to the surface is driven by the repulsion between the A and B segments along the copolymer and the attraction between the B segments and the D sites on the surface. We address the critical role of the commensurability between the copolymer’s monomer sequence distribution and the size and spatial distribution of the surface adsorbing sites on the copolymer adsorption. We show that both copolymer architectures have the ability to recognize the surface motif and transcribe it into the bulk material. Diblock copolymers can transfer the pattern once the heterogeneous domain sizes match the size of the parallel component to the radius of gyration, which is constituted primarily of the adsorbing species. This behavior results from the ability of the diblock copolymer to adopt a brush type conformation. In contrast to the diblocks, copolymers with the alternating sequence distribution are more likely to “zip to” the surface since the adsorbing species are evenly distributed along the copolymer. This chain conformation creates an entropic penalty, which must be alleviated by the formation of loops and tails. These conformational changes endow the alternating copolymer with the ability to recognize patterns with periodicities much less than the parallel component to the radius of gyration, and to invert the pattern as the distance away from the surface is increased.}, number={10}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Semler, JJ and Genzer, J}, year={2003}, month={Sep}, pages={5274–5280} }
 @article{genzer_kramer_fischer_2002, title={Accounting for Auger yield energy loss for improved determination of molecular orientation using soft x-ray absorption spectroscopy}, volume={92}, ISSN={["0021-8979"]}, DOI={10.1063/1.1516258}, abstractNote={Partial (Auger) yield near edge x-ray absorption fine structure (NEXAFS) is a structural analytical technique that has been primarily used to measure the spatial orientation and chemical bonding of small molecules on solid (i.e., inorganic or semiconductor) surfaces. In this article we demonstrate that the building block (BB) scheme proposed by Outka and co-workers [Phys. Rev. Lett. 59, 1321 (1987)] for analyzing NEXAFS spectra can be applied to model the molecular orientation of larger molecules, provided one accounts properly for kinetic energy losses of the Auger electrons traversing through the sample and hence the attenuation in measured Auger yield. We test the applicability of the proposed “modified” BB (MBB) model by measuring the orientation of a self-assembled monolayer (SAM) of –O1.5Si–(CH2)2–(CF2)8F, SF–SAM (SiOx), deposited on top of SiOx-covered silicon wafer as a function of the entrance grid bias (EGB) of the channeltron photoelectron detector. Our measurements of the EGB-dependent electron escape depth reveal that a crude depth profiling within the top ≈5 nm of the sample is possible by increasing the negative EGB on the channeltron detector, at the highest bias thus selecting only the Auger electrons, which have suffered negligible energy loss. In addition, we discuss how the order parameter method introduced recently by Stöhr and Samant [J. Electron Spectrosc. Relat. Phenom. 98–99, 189 (1989)] can be used to determine the molecular orientation of large organic molecules on surfaces. We also show that by accounting for energy losses of the NEXAFS Auger electrons (attenuation of measured Auger yield), the corrected order parameter (COP) approach gives good estimates of the orientation of molecules. We present a comparison between the MBB and COP models using experimental data collected from NEXAFS experiments from semifluorinated (SF) mesogens, –(CH2)x(CF2)yF, which are attached to: (1) the isoprene backbone of polyisoprene or a styrene–isoprene diblock copolymer and (2) a SiOx-covered solid substrate. We show that on both surfaces, the SF groups are oriented and on average are tilted by an angle 〈τF-helix〉 from the sample normal. We show that at higher 〈τF-helix〉 the results from the COP approach agree almost quantitatively with those extracted using the MBB model.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Genzer, J and Kramer, EJ and Fischer, DA}, year={2002}, month={Dec}, pages={7070–7079} }
 @misc{composto_walters_genzer_2002, title={Application of ion scattering techniques to characterize polymer surfaces and interfaces}, volume={38}, ISSN={["1879-212X"]}, DOI={10.1016/S0927-796X(02)00009-8}, abstractNote={Ion beam analysis techniques, particularly elastic recoil detection (ERD) also known as forward recoil spectrometry (Frcs) has proven to be a value tool to investigate polymer surfaces and interfaces. A review of ERD, related techniques and their impact on the field of polymer science is presented. The physics of the technique is described as well as the underlying principles of the interaction of ions with matter. Methods for optimization of ERD for polymer systems are also introduced, specifically techniques to improve the depth resolution and sensitivity. Details of the experimental setup and requirements are also laid out. After a discussion of ERD, strategies for the subsequent data analysis are described. The review ends with the breakthroughs in polymer science that ERD enabled in polymer diffusion, surfaces, interfaces, critical phenomena, and polymer modification.}, number={3-4}, journal={MATERIALS SCIENCE & ENGINEERING R-REPORTS}, author={Composto, RJ and Walters, RM and Genzer, J}, year={2002}, month={Jul}, pages={107–180} }
 @article{wu_efimenko_genzer_2002, title={Combinatorial study of the mushroom-to-brush crossover in surface anchored polyacrylamide}, volume={124}, ISSN={["0002-7863"]}, DOI={10.1021/ja027412n}, abstractNote={We present a method for fabricating anchored polymers with a gradual variation of grafting densities on solid substrates. The technique for generating such structures comprises (i) formation of a molecular gradient of polymerization initiator on the solid substrate and (ii) polymerization from the substrate-bound initiator centers ("grafting from"). We measure the mushroom-to-brush transition in grafted polyacrylamides and show that the mushroom and brush behavior can be described using existing scaling theories.}, number={32}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Wu, T and Efimenko, K and Genzer, J}, year={2002}, month={Aug}, pages={9394–9395} }
 @article{schultz_hall_genzer_2002, title={Computer simulation of copolymer phase behavior}, volume={117}, ISSN={["1089-7690"]}, DOI={10.1063/1.1519839}, abstractNote={Discontinuous molecular dynamics simulation is used to study the phase behavior of diblock copolymers modeled as chains of tangent hard spheres with square shoulder repulsions between unlike species as a function of chain length, volume fraction and interaction strength (χ). The location of the order–disorder transition for a symmetric copolymer is close to the predictions of Fredrickson and Helfand. Our simulation results for packing fractions of 0.35, 0.40, and 0.45 and chain lengths 10 and 20 are summarized in phase diagrams which display disordered, lamellae, perforated lamellae (PL), cylindrical, and BCC spherical (S) phases in the χN versus f plane. These phase diagrams are consistent with phase diagrams from other simulation studies. Contrary to theoretical predictions we observe the PL phase near regions of predicted gyroid stability, and the S phase only in the systems with high packing fraction and long chain length. These discrepancies may be due to the short chain lengths considered, as they are less evident in the 20-bead chains than the 10-bead chains. We examine the structural spacing of the microphases and the variation of that spacing with χN. We also examine the internal energy and entropy and their variation with χN. Our results are consistent with self-consistent field theory results for the strong segregation limit.}, number={22}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Schultz, AJ and Hall, CK and Genzer, J}, year={2002}, month={Dec}, pages={10329–10338} }
 @article{genzer_2002, title={Copolymer adsorption on planar chemically heterogeneous substrates: The interplay between the monomer sequence distribution and interaction energies}, volume={11}, ISSN={["1521-3919"]}, DOI={10.1002/1521-3919(20020601)11:5<481::AID-MATS481>3.0.CO;2-G}, abstractNote={We use three-dimensional self-consistent field model to study the adsorption of A-B copolymers from A-B copolymer/A homopolymer blends on planar substrates comprising two chemically distinct regions C and D. The interplay between the spatial distribution of the surface chemical heterogeneities and the monomer sequence distribution in the copolymer is examined for diblock (A-B), triblock (A-B-A), inverted triblock (B-A-B), and altermating (A-a/t-B) copolymer. Our results demonstrate that when the chemically heterogeneous motifs on the substrate are detected by the copolymer adsorbing segments, the copolymers can transcribe them with high fidelity into three dimensions. The way the surface pattern gets transferred is dictated by the monomer sequence distribution. We show that relative to alternating copolymers, block copolymers are generally better at capturing the chemical pattern shape and transcribing it into the polymer mixture. Moreover, block copolymers with shorter adsorbing blocks are capable of better recognizing the substrate motifs. In order to address the interplay between the monomer sequence distribution in the copolymer and the interaction energies, we systematically vary the repulsion between A and B, and the attraction between B and D. Our calculations reveal that reveal that increasing i) the interaction between the copolymer I adsorbing segments. (B) and the sticky points at the substrate (D), and/or ii) the repuilsion between the copolymer segments (A and B) increases the total amount of the copolymer adsorbed at the mixture/substrate interface, and decreases (increases) the fidelity of the substrate chemical pattern recognition by compositionally symmetric (asymmetric) copolymers.}, number={5}, journal={MACROMOLECULAR THEORY AND SIMULATIONS}, author={Genzer, J}, year={2002}, month={Jun}, pages={481–493} }
 @misc{bhat_fischer_genzer_2002, title={Fabricating planar nanoparticle assemblies with number density gradients}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la025524m}, abstractNote={We report on preparing assemblies of gold nanoparticles with continuous gradients in number density on flat silica-covered substrates. The methodology consists of (i) first forming a one-dimensional molecular gradient of amino groups (−NH2) on the substrate by vapor deposition of amine-terminated silane molecules, followed by (ii) attachment of gold nanoparticles to −NH2 functional groups by immersing the substrate in a colloidal gold solution. Experiments using atomic force microscopy reveal that the number density of nanoparticles on the substrate varies continuously as a function of the position on the substrate. Near-edge X-ray absorption fine structure studies confirm that the nanoparticle number density gradient is closely correlated with the concentration gradient of −NH2 groups anchored to the substrate. We demonstrate that the number density of nanoparticles within the gradient and the length of the gradient can be tuned by controlling the vapor diffusion of silane molecules. In addition we show ...}, number={15}, journal={LANGMUIR}, author={Bhat, RR and Fischer, DA and Genzer, J}, year={2002}, month={Jul}, pages={5640–5643} }
 @article{efimenko_novick_carbonell_desimone_genzer_2002, title={Formation of self-assembled monolayers of semifluorinated and hydrocarbon chlorosilane precursors on silica surfaces from liquid carbon dioxide}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la011813j}, abstractNote={We report on the formation and properties of self-assembled monolayers (SAMs) prepared by depositing semifluorinated and hydrocarbon trichlorosilane precursors, F(CF2)8(CH2)2SiCl3 (F8H2) and H(CH2)18SiCl3 (H18), respectively, from vapor, organic solvent, and liquid CO2 (l-CO2). Contact angle measurements of the SAM deposition kinetics reveal that regardless of the molecule type, the deposition rates from l-CO2 exceed those from vapor or organic solvents by several orders of magnitude. We derive two different transport models describing the formation of SAMs. We show that while the diffusion-limited model is not capable of describing the experimental data, the adsorption-limited model captures the major features of the adsorption kinetics quite well. We apply the results of the adsorption-limited model to conclude that the observed behavior is a consequence of (i) a relatively high bulk concentration (l-CO2 vs vapor) and (ii) higher solution diffusivity (l-CO2 vs organic solvent) of the silanes in l-CO2. N...}, number={16}, journal={LANGMUIR}, author={Efimenko, K and Novick, B and Carbonell, RG and DeSimone, JM and Genzer, J}, year={2002}, month={Aug}, pages={6170–6179} }
 @article{genzer_efimenko_fischer_2002, title={Molecular orientation and grafting density in semifluorinated self-assembled monolayers of mono-, di-, and trichloro silanes on silica substrates}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la025921x}, abstractNote={Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to measure the molecular orientation in semifluorinated self-assembled monolayers (SAMs) prepared by vapor deposition of mono- (F3C(CF2)8(CH2)2Si(CH3)2Cl, m-F8H2), di- (F3C(CF2)8(CH2)2Si(CH3)Cl2, d-F8H2), and trichloroorganosilanes (F3C(CF2)8(CH2)2SiCl3, t-F8H2) on flat silica-covered substrates. The average tilt angles (from the sample normal) of the fluorocarbon part, F(CF2)8-, of t-F8H2, d-F8H2, and m-F8H2 measured by carbon K-edge NEXAFS are 10 ± 2°, 35 ± 2°, and 45 ± 3°, respectively. We show that the increase of the tilt angle is associated with the steric hindrance of the methyl groups attached to silicon close to the bonding substrate. We also show that the molecular orientation obtained from the NEXAFS measurements can be used to estimate the grafting densities of the F8H2 molecules on the substrates. We present a simple one-dimensional geometric model to show that the grafting density of m-F8H2 is approximately one-half of t...}, number={24}, journal={LANGMUIR}, author={Genzer, J and Efimenko, K and Fischer, DA}, year={2002}, month={Nov}, pages={9307–9311} }
 @article{efimenko_wallace_genzer_2002, title={Surface modification of Sylgard-184 poly(dimethyl siloxane) networks by ultraviolet and ultraviolet/ozone treatment}, volume={254}, DOI={10.1006/jcis.202.8594}, number={2}, journal={Journal of Colloid and Interface Science}, author={Efimenko, Kirill and Wallace, W. E. and Genzer, Jan}, year={2002}, pages={306–315} }
 @article{genzer_2001, title={Copolymer adsorption on planar substrates with a random distribution of chemical heterogeneities}, volume={115}, ISSN={["1089-7690"]}, DOI={10.1063/1.1391254}, abstractNote={We use a 3D SCF model of polymer adsorption to investigate the adsorption of A-B copolymers from A-B/homopolymer A mixtures onto planar substrates composed of two chemically distinct randomly distributed sites, one of which has a preferential affinity for the B segments of the copolymer. Our results show that when the chemically heterogeneous substrate motifs are recognized by the copolymer, the copolymers can transcript them with a relatively high fidelity into three dimensions. The way the surface motif is transferred is strongly dictated by the copolymer sequence. We show that block copolymers are capable of detecting small clusters of the substrate adsorption sites. The fidelity of the pattern shape and the distance from the substrate to which the pattern gets transferred increases with decreasing the length of the adsorbing block of the copolymer. Our results also indicate that increasing (i) the interactions between the copolymer adsorbing segments and the “sticky” points at the substrate, and/or (ii) the repulsion between the copolymer segments increases the total adsorbed amount of the copolymer at the mixture/substrate interface but it decreases the fidelity of the substrate chemical pattern transfer into the mixture. We show that, in contrast to the block copolymers, macromolecules with alternating sequence distributions adopt different conformations on random substrates in that they tend to localize at the boundaries between the C/D surface sites, where the substrate chemical pattern more closely matches the sequence distribution of the B stickers along the copolymer. We claim that this feature allows us to use alternating copolymers in situations where one needs to suppress the chemical pattern transfer on such random substrates.}, number={10}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Genzer, J}, year={2001}, month={Sep}, pages={4873–4882} }
 @article{genzer_2001, title={Copolymer-assisted generation of three-dimensional patterns by replicating two-dimensional substrate motifs - art. no. 022601}, volume={6302}, number={2}, journal={Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics}, author={Genzer, J.}, year={2001}, pages={2601} }
 @article{efimenko_genzer_2001, title={How to prepare tunable planar molecular chemical gradients}, volume={13}, ISSN={["0935-9648"]}, DOI={10.1002/1521-4095(200110)13:20<1560::AID-ADMA1560>3.0.CO;2-Z}, abstractNote={Mechanically assembled monolayers (MAMs) can be employed to adjust the surface density of the initiators and consequently that of molecular gradients prepared on flexible supports. The steepness and the position of the gradient of molecules on a substrate are fine-tuned by a combination of grafting and mechanical manipulation of the films. Planar molecular gradients ranging from several millimeters to several centimeters can thus be fabricated. In addition, the wetting properties of the hydrophobic part of the substrate can be adjusted by altering the chemical nature of the films.}, number={20}, journal={ADVANCED MATERIALS}, author={Efimenko, K and Genzer, J}, year={2001}, month={Oct}, pages={1560-+} }
 @article{wallace_fischer_efimenko_wu_genzer_2001, title={Polymer chain relaxation: Surface outpaces bulk}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma002075t}, abstractNote={Introduction: The time scale that controls polymer chain relaxation profoundly influences the economics of industrial plastics processing. However, not much is known about how fast the surface relaxes relative to the bulk in amorphous polymeric materials. This is in part because no study has reported simultaneous measurement of both surface and bulk chain relaxation dynamics on a single macroscopic sample. In this work we show how carbon near-edge X-ray absorption fine structure (NEXAFS) can be applied to detect both surface and bulk segmental relaxation in uniaxially deformed polystyrene samples. We show that by simultaneously monitoring the partial electron yield (PEY, kinetic energy > 150 eV) and the fluorescence yield (FY, carbon Kα 277eV) NEXAFS signals, with probing depths of approximately 2 and 200 nm, respectively, one can examine segmental motion throughout a polymer sample. Using this methodology, chain relaxation is found to occur approximately 30% faster at the surface than in the bulk. Methods and Materials: Rectangular samples (12.5 x 12.5 x 6 mm), prepared by vacuum hot-pressing at 150 °C monodisperse polystyrene (M = 228,000 g/mole), were placed into a steel channel die and uniaxially elongated at room temperature along one of the long dimensions to about 130% of their original length. This sample preparation allowed us to examine true bulk samples as encountered in industrial practice and to avoid thin film effects that may alter the free surface behavior. The NEXAFS experiments were conducted on the U7A NIST/Dow Materials Characterization end-station at the National Synchrotron Light Source at Brookhaven National Laboratory. For each sample the PEY and FY carbon K-edge NEXAFS intensities were measured with the incident polarized X-ray beam normal to the sample surface and at two azimuthal sample orientations:with the electric field vector, E, parallel (φ = 0°) and perpendicular (φ = 90°) to the elongation direction as shown in Fig. 1. Results: Orientation of the chain backbone was determined by monitoring the C=C phenyl ring 1s → π1* NEXAFS resonance intensity at 285.5 eV, which involves the excitation of carbon 1s electrons to the unfilled π* antibonding orbitals of the phenyl ring. Enhancement of the 1s → π1* resonance intensity was observed when E was parallel to the elongation direction. Since the phenyl π* orbitals are oriented normal to the phenyl rings, and the phenyl rings, free to rotate around the pendant bond, will have a component normal to the chain axis, the intensity of the π* signal has been shown to be an unambiguous signature of backbone orientation. This orientation, seen both in the PEY and the FY NEXAFS signals of the elongated samples, provides clear evidence of chain orientation at the outset of the experiment. A direct measure of the chain relaxation rates at the surface and in the bulk can be obtained by defining an orientation factor, OF (see Fig. 1 caption) that is evaluated from the time dependence of the 1s → π1* resonance intensity in the PEY and FY NEXAFS spectra, respectively, during annealing. Figure 1 shows that while the OF for both surface and bulk chains decays as a function of increasing annealing time at 60 °C, the surface orientation is initially greater and decays faster than for the bulk. Fitting the decay rates to exponential functions gives characteristic time constants of approximately 33 and 43 minutes for the surface and the bulk, respectively. Conclusions: These results show conclusively that polystyrene surface chain relaxation dynamics are significantly faster than the bulk. Recalling that chain relaxation rates in amorphous polymers increase with decreasing number of entanglements, our results are in agreement with recent theory that predicts the number of entanglements at the free surface to be significantly reduced compared to the bulk. Acknowledgments: This research was supported by NSF CAREER (JG) and NCSU FR&PD Grant (JG). Figure 1. Time evolution of the orientation factor, OF, from an elongated (oriented) polystyrene sample reveals that when annealed at 60 °C the surface chains relax to an equilibrium (unoriented) configuration faster than the bulk chains. OF is calculated from (I|| I⊥)/(I|| + I⊥), where I|| and I⊥ are the 1s → π1* resonance NEXAFS intensities collected with the sample elongation direction parallel (φ = 0°) and perpendicular (φ = 90°) to the electric vector of the soft Xray beam, E, respectively. 0 40 80 120 10 10 10}, number={15}, journal={MACROMOLECULES}, author={Wallace, WE and Fischer, DA and Efimenko, K and Wu, WL and Genzer, J}, year={2001}, month={Jul}, pages={5081–5082} }
 @article{wu_efimenko_genzer_2001, title={Preparing high-density polymer brushes by mechanically assisted polymer assembly}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma001750w}, abstractNote={It is well-known that when polymers are endanchored in a sufficient concentration to a substrate, they form a so-called polymer “brush” whereby the chains are stretched with respect to their preferred configuration away from the interface. The characteristics of polymer brushes have been analyzed using a variety of theoretical methods and experimental probes and are now fairly well established.1-4 For example, the thickness of the brush layer, H, is known to depend linearly on the number of repeat units of the polymer, N, and on the power law of the brush grafting density at the substrate, σ, with the exponent of /3 or 1, depending on the surface coverage.1,2 To fine-tune the polymer brush properties, one needs to have a good control over H and σ. While H can be adjusted by simply varying the polymerization time, monomer concentration, and monomer conversion, σ depends on the methods by which polymer brushes are formed. Previous reports established that polymer brushes with moderately high grafting densities can be prepared by harnessing the “grafting from” principle in which the polymer chains are synthesized using radical initiators that are covalently bound to the substrate. A vast majority of experiments involved classical radical growth methods with either azo(e.g., AIBN) or peroxide-based initiators that either were created directly on the substrate or were attached to the substrate via selfassembly.5-11 While the advantage of such methods is their ease of use and the ability to prepare brushes from a variety of monomers, a major disadvantage is a hardto-control polymerization process, which usually leads to brushes with broad molecular weight distributions. Recently several reports appeared that described the formation of polymer brushes using surface-initiated “living” radical polymerization,12 such as the atom transfer radical polymerization (ATRP).13,14 Because of its simplicity, robustness, and the ability to synthesize polymers with narrow molecular weight distributions, ATRP has been the method of choice for most surfaceinitiated “living” radical polymerization processes.15-21 As mentioned previously, one of the crucial parameters governing the behavior of polymer brushes is their grafting density at the polymer/substrate interface. The “grafting from” techniques offer a fairly good control over the grafting density of the polymer brushsin the ideal case σ is simply equal to the surface density of the polymerization initiators. While a relatively high density of initiators can be achieved by assembling the molecules on the surface by means of LangmuirBlodgett (LB) techniques17,20 or by forming organized self-assembled monolayers (SAMs),19 tailoring the grafting density of the SAM chains is not an easy task. SAMs are usually formed through self-assembly processes that are governed by the chemical and structural nature of the SAM molecules and the means of their attachment to the substrate. To overcome this limitation, one would need to seek another way of controlling the grafting density of the surface initiators that is independent of the system thermodynamics. Recently, we have demonstrated that one can finetune the grafting density of molecules on surfaces by fabricating MAMs (“mechanically assembled monolayers”), structures that are based on the combination of natural self-assembly and mechanical manipulation of the grafted molecules on surfaces.22 In this work we utilize the MAMs to adjust the surface density of the initiators and consequently that of polymer brushes grown by surface-initiated ATRP. Following the steps involved in the preparation procedure (see below), we call this technique MAPA (“mechanically assisted polymer assembly”). In this communication we illustrate the principles of MAPA on preparing dense polymer brushes of polyacrylamide (PAAm).15 Figure 1 shows schematically how PAAm-MAPA works. First, a pristine PDMS network film was prepared (cf. Figure 1a) by casting a mixture of PDMS and a cross-linker24 into a thin (≈1 mm) film and curing it at 70 °C for about an hour. The film was then cut into small strips (≈1 × 5 cm2) and mechanically uniaxially elongated by ∆x (cf. Figure 1b). Subsequent exposure to UV/ozone (UVO) treatment produced hydrophilic PDMS surfaces (PDMS-UVO) composed mainly of hydroxyl groups (HO-[Si]surface) that served as attachments points for chlorosilane-based ATRP initiators. Following previous work on PAAm brushes, we used 1-trichlorosilyl-2-(m-p-chloromethylphenyl)ethane (CMPE) (United Chemical Technologies, Inc.) as the initiator. The CMPE molecules were deposited from vapor25 onto this stretched substrate (cf. Figure 1d) and formed an organized CMEP-SAM following the well-known set of reactions:}, number={4}, journal={MACROMOLECULES}, author={Wu, T and Efimenko, K and Genzer, J}, year={2001}, month={Feb}, pages={684–686} }
 @article{martinache_royer_siripurapu_henon_genzer_khan_carbonell_2001, title={Processing of polyamide 11 with supercritical carbon dioxide}, volume={40}, ISSN={["0888-5885"]}, DOI={10.1021/ie010410b}, abstractNote={The supercritical carbon dioxide induced swelling and plasticization of polyamide 11 were investigated. The swelling kinetics exhibit an initial region of large swelling, in which the diffusion of CO2 into the polymer follows Fickian behavior, and a subsequent region of small volume increase that asymptotically approaches an equilibrium swelling value. The diffusion coefficient of CO2 in polyamide 11 was calculated from the initial slope of the swelling kinetics data. CO2, injected up to 3 wt % using an extrusion rheometer, is shown to be an effective plasticizer for polyamide 11, lowering the viscosity of the polymer melt by as much as 50%. The use of CO2 as a blowing agent was also investigated, and we report preliminary foaming attempts using a batch process. We obtained homogeneously distributed foams, featuring well-defined closed cells with an average diameter of 30 μm that had an unfoamed skin layer.}, number={23}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Martinache, JD and Royer, JR and Siripurapu, S and Henon, FE and Genzer, J and Khan, SA and Carbonell, RG}, year={2001}, month={Nov}, pages={5570–5577} }
 @article{genzer_2001, title={Self-consistent field study of copolymer adsorption at planar chemically 'rough' surfaces: an interplay between the substrate chemical pattern and copolymer sequence distribution}, volume={94}, ISSN={["0001-8686"]}, DOI={10.1016/S0001-8686(01)00057-4}, abstractNote={We extend the one-dimensional self-consistent field (SCF) scheme of Scheutjens-Fleer to three dimensions (3D) and use this three-dimensional SCF model to investigate the adsorption of A–B copolymers from A homopolymer matrices onto planar substrates composed of two chemically distinct sites (C and D), one of which has a preferential affinity for the B segments of the copolymer. To address the role of the substrate chemical heterogeneity on copolymer adsorption, we keep the fraction of the C and D sites constant (50% of each site) and vary their spatial distribution on the substrate. The interplay between the surface chemical heterogeneity and the chain microstructure is examined for A–B diblock, A–B–A, B–A–B triblock, and A–alt–B alternating copolymers. Our results indicate that regardless of the type of the surface chemical heterogeneity, the A–B diblock and triblock copolymers adopt ‘brush’-like and ‘bridge’-like structures, respectively, with the B block being anchored to the substrate. In contrast, the A–alt–B macromolecule is found to be ‘zipped’ to the substrate. For a fixed chemical potential of the copolymer in the A–B/A mixture and the surface adsorption energy of B, the amount of the adsorbed copolymer depends on: (1) the number of the B segments; (2) the copolymer microstructure; and (3) the distribution of the C and D regions on the substrate. Three-dimensional maps of the spatial density of copolymer segments provide insight into copolymer conformation at the mixture/substrate interface and also the ability of the copolymer to recognize and mimic the substrate pattern. In addition, we discuss the circumstances under which the substrate pattern is transferred deep inside the A–B/A mixture and those, which lead to strong damping of the substrate motif as one moves away from the substrate/mixture interface.}, number={1-3}, journal={ADVANCES IN COLLOID AND INTERFACE SCIENCE}, author={Genzer, J}, year={2001}, month={Nov}, pages={105–134} }
 @article{genzer_efimenko_2000, title={Creating long-lived superhydrophobic polymer surfaces through mechanically assembled monolayers}, volume={290}, ISSN={["1095-9203"]}, DOI={10.1126/science.290.5499.2130}, abstractNote={We show that elastomeric surfaces can be tailored using “mechanically assembled monolayers” (MAMs), structures that are fabricated by combining self-assembly of surface grafting molecules with mechanical manipulation of the grafting points in the underlying elastic surface. The versatility of this surface modification method is demonstrated by fabricating MAMs with semifluorinated (SF) molecules. These SF-MAMs have superior nonwetting and barrier properties in that they are “superhydrophobic” and nonpermeable. We also establish that these material characteristics do not deteriorate even after prolonged exposure to water, which usually causes surface reconstruction in conventionally prepared SF self-assembled monolayers.}, number={5499}, journal={SCIENCE}, author={Genzer, J and Efimenko, K}, year={2000}, month={Dec}, pages={2130–2133} }
 @article{manias_chen_krishnamoorti_genzer_kramer_giannelis_2000, title={Intercalation kinetics of long polymers in 2 nm confinements}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma0009552}, abstractNote={The motion of confined polymers is measured experimentally between parallel, atomically smooth solid surfaces, separated by 2 nm. In particular, the kinetics of intercalation of monodispersed polystyrene in alkylammonium modified mica-type silicates were studied using X-ray diffraction. The kinetics of the neat polymers and their functionalized derivatives were measured as functions of molecular weight, extent of functionalization, and silicate surface organic modification, at various temperatures. Selective corroborative studies were also performed using in-situ small-angle neutron scattering (SANS). The kinetic data are interpreted in terms of an effective diffusion coefficient (Deff) of the polymer, which undergoes a dramatic decrease with stronger silicate surface-polymer interaction. This interaction is varied by either changing the silicate surface modification or by increasing the extent of functionalization of the polystyrene chains. Furthermore, the diffusion coefficient exhibits an inverse dependence on chain length (N), i.e., Deff ∝ N -1 , for chains up to 900 000 molecular weight.}, number={21}, journal={MACROMOLECULES}, author={Manias, E and Chen, H and Krishnamoorti, R and Genzer, J and Kramer, EJ and Giannelis, EP}, year={2000}, month={Oct}, pages={7955–7966} }
 @article{genzer_sivaniah_kramer_wang_xiang_char_ober_bubeck_fischer_graupe_et al._2000, title={Molecular orientation of single and two-armed monodendron semifluorinated chains on "soft" and "hard" surfaces studied using NEXAFS}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma991710w}, abstractNote={Near-edge absorption fine structure (NEXAFS) measurements are used to probe the molecular orientation of semifluorinated (SF) mesogens, −(CH2)x(CF2)yF, which are attached to (i) the isoprene backbone of polyisoprene or a styrene-isoprene diblock copolymer (“soft” substrate), and (ii) a Au-covered solid substrate via a thiol link (“hard” substrate). The SF groups on both surfaces are oriented and on average are tilted from the sample normal. The tilt angle, 〈τF-helix〉, of the fluorinated part of the SF group on each substrate is determined exclusively by the combination of x and y, increasing with increasing x and with decreasing y. Moreover, 〈τF-helix〉 is found to be independent of the surface topology (flat surfaces vs surfaces covered with holes or islands of the copolymer), casting solvent, and the architecture of the SF group (single vs 2-armed monodendron). Comparing the orientation of the SF groups on both substrates reveals that 〈τF-helix〉 is approximately 14° higher on the “soft” substrate.}, number={16}, journal={MACROMOLECULES}, author={Genzer, J and Sivaniah, E and Kramer, EJ and Wang, JG and Xiang, ML and Char, K and Ober, CK and Bubeck, RA and Fischer, DA and Graupe, M and et al.}, year={2000}, month={Aug}, pages={6068–6077} }
 @misc{genzer_efimenko_2000, title={Tailoring the grafting density of organic modifiers at solid/liquid interfaces}, volume={6,423,372}, number={2000 Dec 13}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Genzer, J. and Efimenko, K.}, year={2000} }
 @article{genzer_sivaniah_kramer_wang_korner_xiang_char_ober_dekoven_bubeck_et al._2000, title={The orientation of semifluorinated alkanes attached to polymers at the surface of polymer films}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma991182o}, abstractNote={The surface molecular orientation of a liquid crystalline (LC) layer made up of semifluorinated (SF) single side groups [−CO−(CH2)x-1−(CF2)yF] (single SF groups) attached to polyisoprene homopolymer or the isoprene block of a styrene−isoprene diblock copolymer was determined by analyzing the partial electron yield C-edge NEXAFS signal. The results show that the surfaces of thin SF polymer films are covered with a uniform layer, consisting of the SF−LC groups whose average −CF2− tilt angle with the surface normal lies in the range 29−46°. This is in direct contrast to the bulk, where the directors of the SF−LC mesogens are aligned parallel to the polystyrene/SF−polyisoprene interface of the block copolymers. This average tilt angle increases with increasing the length of the −(CH2)x-1− group (x increases) but decreases with increasing the length of the −(CF2)y− part of the molecule (y increases) at constant x.}, number={5}, journal={MACROMOLECULES}, author={Genzer, J and Sivaniah, E and Kramer, EJ and Wang, JG and Korner, H and Xiang, ML and Char, K and Ober, CK and DeKoven, BM and Bubeck, RA and et al.}, year={2000}, month={Mar}, pages={1882–1887} }
 @article{oslanec_genzer_faldi_composto_garrett_1999, title={Surface enrichment in a miscible random copolymer blend: Influence of polydispersity and architecture}, volume={32}, ISSN={["0024-9297"]}, DOI={10.1021/ma980601z}, abstractNote={Neutron reflectivity and low-energy forward-recoil spectrometry were used simultaneously to monitor surface segregation in blends of poly(styrene-ran-acrylonitrile), dSAN23 and SAN27, having 23 and 27 wt % AN, respectively. Because of its lower AN content, dSAN23 was found to partition at the polymer/air interface, in agreement with the work of Mansfield et al. (Physica B 1991, 173, 207) and Kim et al. (Polymer 1995, 36, 2427). In contrast to the previous studies, this work explores surface segregation at high dSAN23 bulk volume fractions, φ∞ (i.e., φ∞ > 0.50). New results include the observation of a maximum dSAN23 surface excess (∼75 A) near φ∞ ≈ 0.35 and a dSAN23 surface volume fraction that approaches 1, rather than 0.75, as φ∞increases to 1. The dSAN23 profile deviates from the exponential profile predicted by Schmidt−Binder and self-consistent mean-field (SCMF) models. For φ∞ > 0.50, the profile displays a surface flattening not observed at low φ∞. The SCMF model is extended to account for polymer p...}, number={12}, journal={MACROMOLECULES}, author={Oslanec, R and Genzer, J and Faldi, A and Composto, RJ and Garrett, PD}, year={1999}, month={Jun}, pages={4098–4105} }
 @article{genzer_sivaniah_kramer_wang_korner_char_ober_dekoven_bubeck_fischer_et al._2000, title={Temperature dependence of molecular orientation on the surfaces of semifluorinated polymer thin films}, volume={16}, ISSN={["0743-7463"]}, DOI={10.1021/la9910327}, abstractNote={Near-edge X-ray absorption fine structure is used to investigate the temperature dependence of molecular orientation of semifluorinated liquid crystalline (SF-LC) mesogens, which are attached to the modified isoprene backbone of (i) a poly(1,2-isoprene) homopolymer and (ii) a diblock copolymer consisting of polystyrene and poly(1,2-isoprene) blocks. Our experiments reveal the existence of two temperature regions in which the surface orientation of the SF-LC mesogens changes abruptly, but even 30 K above the highest such temperature region the surface orientation does not become isotropic. The lower temperature surface transition for both homopolymer and block copolymer occurs close to the temperature of the bulk homopolymer smectic-B to smectic-A transition and well above the bulk smectic-B to smectic-A transition in the block copolymer. It seems to be controlled exclusively by the ordering phenomena originating from the surface. In contrast, the change in the surface organization of the SF-LC mesogens at...}, number={4}, journal={LANGMUIR}, author={Genzer, J and Sivaniah, E and Kramer, EJ and Wang, JG and Korner, H and Char, K and Ober, CK and DeKoven, BM and Bubeck, RA and Fischer, DA and et al.}, year={2000}, month={Feb}, pages={1993–1997} }
 @article{genzer_composto_1999, title={The interface between immiscible polymers studied by low-energy forward recoil spectrometry and neutron reflectivity}, volume={40}, ISSN={["0032-3861"]}, DOI={10.1016/s0032-3861(98)00664-8}, abstractNote={The superb depth resolution of low-energy, forward recoil, spectrometry, (LE-FRES), is demonstrated by measuring the interfacial profile between 1,4-polybutadiene (PB), and deuterated polystyrene (dPS), at 175°C. To enhance depth resolution, the top dPS layer is ‘thinned’ by ion sputtering, prior to LE-FRES analysis, to achieve a resolution of 13 nm at the interface. An interfacial width of 6.0±3.5 nm is measured. To compliment this study, neutron reflectivity (NR) is used to determine the interfacial volume fraction profile between PB and an isotopic mixture of polystyrene (dPS:PS) having a dPS volume fraction of 0.30. After annealing at 175°C, the interface broadens to 3.3 nm. However, no interfacial segregation of dPS or PS is observed suggesting that the difference between the PB–dPS and PB–PS interaction parameters (χ) is insufficient to drive interfacial segregation. Using a self-consistent field model (SCF) and known values of χ, the width is calculated to be 2.2 nm. By adding capillary wave broadening, this width increases to 2.8 nm, in better agreement with the NR value. In agreement with the NR measurement, the SCF model predicts no segregation of dPS or PS.}, number={15}, journal={POLYMER}, author={Genzer, J and Composto, RJ}, year={1999}, month={Jul}, pages={4223–4228} }
 @article{heier_genzer_kramer_bates_walheim_krausch_1999, title={Transfer of a chemical substrate pattern into an island-forming diblock copolymer film}, volume={111}, ISSN={["0021-9606"]}, DOI={10.1063/1.480469}, abstractNote={We investigate the transfer of a chemical pattern on a substrate into a symmetric diblock copolymer thin film of poly(styrene-2-vinylpyridine) (PS-PVP). The substrates have patterns of self-assembled monolayers (SAMs) produced by microcontact printing H3C-terminated (H3C-) SAM stripes alternating with HO-terminated (HO-) SAM stripes. The PS-PVP lamellae over the H3C-SAM have a defect structure that attracts excess PS-PVP that would normally form islands on a uniform HO-SAM stripe. We seek to understand the process that limits our ability to accommodate all excess polymers on top of the H3C-SAM. In the early stages of annealing, waves of thickness develop from the H3C/HO-SAM boundary and propagate into the film over the HO-SAM. For very short annealing times, the wavelength λ of these thickness waves is constant at any given time for all grating periodicities. Large amplitude patterns develop when λ=2d/(2n−1), where d is the width of the HO-SAM stripe and n is an integer ⩾1. Such patterns suggest constructive interference of the thickness waves and indeed much lower amplitudes over the HO-SAM stripes are observed when λ=d/n (destructive interference). This behavior seems close to that seen for surface-directed spinodal decomposition waves in thin films of binary polymer mixtures. We achieve more complete transfer of excess copolymers from the HO-SAM stripe to the H3C-SAM ones if the film is preordered under a confining layer that does not permit the formation of surface features.}, number={24}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Heier, J and Genzer, J and Kramer, EJ and Bates, FS and Walheim, S and Krausch, G}, year={1999}, month={Dec}, pages={11101–11110} }
 @article{genzer_heier_kramer_1999, title={Wetting reversal transition in phase-separated polymer mixtures}, volume={139}, ISSN={["1521-3900"]}, DOI={10.1002/masy.19991390109}, abstractNote={AbstractWe investigate a wetting reversal transition in thin films of two‐phase mixtures of poly(ethylene‐propylene) (PEP) and its deuterated analogue (dPEP) on a substrate covered by a self‐assembled monolayer (SAM) whose surface energy, γSAM, is tuned by varying the SAM composition. As γSAM increases from 21 to 24 mJ/m2, a transition from a three‐layer (air/dPEP/PEP/dPEP/SAM) to a two‐layer (air/dPEP/PEP/SAM) structure occurs at increasing Tc ‐ T, where Tc and T are the critical and transition temperatures, respectively. As the system structure changes from three‐layer to two‐layer, the thicknesses of the dPEP‐rich wetting layers at the air/mixture and mixture/SAM interfaces are found to smoothly increase and decrease, respectively, while the thickness of the PEP‐rich layer (ca. one half of the total film thickness) does not change. The dependence of the transition temperature on γSAM is predicted by a simple model using the experimental data on the surface energies of PEP/dPEP and estimates of the interfacial energy between PEP and dPEP.}, number={1999 Apr.}, journal={MACROMOLECULAR SYMPOSIA}, author={Genzer, J and Heier, J and Kramer, EJ}, year={1999}, month={Apr}, pages={77–85} }
 @article{genzer_composto_1998, title={Effect of molecular weight on the interfacial excess, tension, and width in a homopolymer binary polymer blend system}, volume={31}, ISSN={["0024-9297"]}, DOI={10.1021/ma970993u}, abstractNote={The interfacial properties of a three-component, two-phase A/B:C blend are investigated to understand the effect of the A and B chain lengths on the interfacial excess of B, zB*, the interfacial tension, γABC, and the interfacial width, wABC. The A/B:C components are polystyrene/poly(d8-styrene-co-4-bromostyrene):poly(styrene-co-4-bromostyrene), where B and C have 4-bromostyrene mole fractions of 0.154 and 0.177, respectively. Low-energy forward recoil spectrometry (LE-FRES) is used to measure zB* as a function of the B volume fraction in the B:C blend, φB∞. The experimental zB*'s are found to be in excellent agreement with those calculated using the self-consistent field (SCF) model of the A/B:C interface. In addition, the SCF model is used to evaluate γABC and the widths for the A/B:C, A/B, and A/C interfaces (i.e., wABC, wAB, and wAC, respectively). Our results demonstrate that increasing the number of B segments, NB, greatly increases the magnitude of zB*, particularly at low φB∞. On the other hand, v...}, number={3}, journal={MACROMOLECULES}, author={Genzer, J and Composto, RJ}, year={1998}, month={Feb}, pages={870–878} }
 @article{genzer_kramer_1998, title={Pretransitional thinning of a polymer wetting layer}, volume={44}, ISSN={["0295-5075"]}, DOI={10.1209/epl/i1998-00454-4}, abstractNote={Mixtures of two immiscible polymers A and B phase-separate into A-rich (α) and B-rich (β) phases. Thin films of such mixtures exhibit a transition from an equilibrium 3-layer structure (substrate/α/β/α/air) to a 2-layer structure (substrate/β/α/air) as the surface energy of the substrate is increased. In this letter we show that as an (equilibrium) precursor to this transition, the thickness of the α layer in the 3-layer structure at the substrate/polymer interface decreases, while that of the α layer against air increases until the α layer against the substrate vanishes leaving the 2-layer structure. This pretransitional behavior originates from the long-range nature of the van der Waals interaction between layers and is predicted by a simple model that considers the dependence of the free energies of the two α layers on their thicknesses.}, number={2}, journal={EUROPHYSICS LETTERS}, author={Genzer, J and Kramer, EJ}, year={1998}, month={Oct}, pages={180–185} }
 @article{genzer_composto_1997, title={A self-consistent field study of the wetting transition in binary polymer blends}, volume={106}, ISSN={["0021-9606"]}, DOI={10.1063/1.473222}, abstractNote={A self-consistent field approach is used to investigate the partial to complete wetting transition for an A:B polymer blend at coexistence where polymers A and B have equal numbers of segments, N. The surface free energy, Fs, is modeled using the quadratic form suggested by Schmidt and Binder [J. Phys. II (France) 46, 1631 (1985)], namely, Fs=−μφ1−0.5gφ12, where μ and g are the surface equivalents of the bulk chemical potential and interaction energy, respectively, and φ1 is the surface volume fraction of the surface preferred component (A). For selected values of g and the bulk volume fraction of A, φ∞, the volume fraction profile and A surface excess, z*, are calculated as a function of increasing μ. The first and second order wetting transitions are indicated by a discontinuity and divergence, respectively, of z* and φ1. In our simulations, at high values of φ∞ only first order transitions are detected for both N=100 and N=1000. However, both first and second order wetting transitions are observed for low values of φ∞ depending on the value of g. The latter results contrast with those of Carmesin and Noolandi [Macromolecules 22, 1689 (1989)], who found that only first order wetting transitions are possible polymer mixtures. However, our results are in agreement with recent Monte Carlo simulations carried out by Wang and Binder [J. Chem. Phys. 94, 8537 (1991)] and Pereira and Wang [J. Chem. Phys. 104, 5294 (1996)].}, number={3}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Genzer, J and Composto, RJ}, year={1997}, month={Jan}, pages={1257–1263} }
 @article{genzer_composto_1997, title={Surface segregation amplification in miscible polymer blends near criticality}, volume={38}, ISSN={["0295-5075"]}, DOI={10.1209/epl/i1997-00221-7}, abstractNote={In atomic, small molecule or polymeric multicomponent materials, surface compositions naturally differ from the bulk because one component (or phase) will generally favor the surface region. Binary polymer blends represent a model system to investigate surface enrichment because segregation is enhanced by the small combinatorial entropy of mixing and amplified by chain connectivity (relative to small-molecule systems). Therefore, polymers are advantageous systems for probing the thermodynamic complexities underlying surface enrichment in mixtures. In this work, the surface excess of binary polymer blends is studied as a function of composition and temperature in the vicinity of the critical point. Although the surface excess away from criticality behaves as anticipated, it is found to grow slower than expected as criticality is approached from the one-phase region. These results suggest that the surface and bulk thermodynamics are coupled.}, number={3}, journal={EUROPHYSICS LETTERS}, author={Genzer, J and Composto, RJ}, year={1997}, month={Apr}, pages={171–176} }
 @article{genzer_kramer_1997, title={Wetting of substrates with phase-separated binary polymer mixtures}, volume={78}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.78.4946}, abstractNote={We investigate a wetting reversal transition in thin films of two-phase mixtures of poly(ethylenepropylene) (PEP) and its deuterated analog (dPEP) on substrates covered by self-assembled monolayers (SAM) whose surface energy, gSAM, is tuned by varying the SAM composition. As gSAM increases from 21 to 24 mJ m2, a transition from a dPEP PEP dPEP SAM to a dPEP PEP SAM structure occurs at increasing TC 2 T , where TC and T are the critical and transition temperatures, respectively. The dependence of T on gSAM is predicted by a simple model from surface and interfacial energies of PEP dPEP. [S0031-9007(97)03445-5]}, number={26}, journal={PHYSICAL REVIEW LETTERS}, author={Genzer, J and Kramer, EJ}, year={1997}, month={Jun}, pages={4946–4949} }
 @article{genzer_faldi_composto_1996, title={Mean-field theory of the interface between a homopolymer and a binary-polymer mixture}, volume={105}, ISSN={["0021-9606"]}, DOI={10.1063/1.472936}, abstractNote={In this paper we investigate the properties of the interface between a homopolymer (A) and a binary polymer mixture (B:C). We have extended the self-consistent field (SCF) model of Helfand [Macromolecules 25, 1676 (1992)] by including the effects of the numbers of segments of polymers on the polymer volume fractions, the interfacial excess of B, zB*, the interfacial tension, γABC, the interfacial width, wABC, and the A–B interfacial overlap, wAB. Other parameters include the polymer interaction parameters, χAB, χAC, and χBC, and the B volume fraction in the B:C mixture, φB∞. As expected, the B component segregates to the A/B:C interface when A–B interactions are more favorable than the A–C ones (χAB<χAC). This interfacial adsorption lowers the interfacial tension and width compared to the pure A/C case, demonstrating the compatibilizing effect of B. As χBC varies from favorable to unfavorable, B segregation is found to increase. Similarly, at constant interaction parameters, B segregation increases as the number of the B segments increases. Furthermore, the addition of a small amount of high molecular weight B to an immiscible A/C blend is found to reduce greatly γABC and thus stabilize the system. Calculations for the case of an athermal mixture B:C with χAB=χAC reveals that the shorter chains are ‘‘entropically driven’’ to the A/B:C interface.}, number={22}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Genzer, J and Faldi, A and Composto, RJ}, year={1996}, month={Dec}, pages={10134–10144} }
 @article{genzer_faldi_oslanec_composto_1996, title={Surface enrichment in a miscible polymer blend: An experimental test of self-consistent field and long-wavelength approximation models}, volume={29}, ISSN={["0024-9297"]}, DOI={10.1021/ma951108f}, abstractNote={Neutron reflectivity (NR) and low-energy forward recoil spectrometry (LE-FRES) were used to study surface enrichment in miscible blends of deuterated polystyrene, d-PS, and poly(styrene-co-4-bromostyrene), PBr0.049S, having a 0.049 mole fraction of 4-bromostyrene units. The d-PS component was found to segregate preferentially to the polymer blend/air interface, whereas no enrichment of either component was detected at the polymer blend/silicon interface. The experimental values of the surface concentration, φ1, and the surface excess, z*, of d-PS were interpreted using both the theory of Schmidt and Binder (SB) (J. Phys. II (Paris) 1985, 46, 1631) and the self-consistent field (SCF) approach of Genzer et al. (Phys. Rev. E 1994, 50, 2373). Although both SB and SCF models were found to be in good qualitative agreement with the experimentally measured values of φ1 and z*, we demonstrate that the latter proves to be in better quantitative agreement with the experimental results. Moreover, a comparison of the ...}, number={16}, journal={MACROMOLECULES}, author={Genzer, J and Faldi, A and Oslanec, R and Composto, RJ}, year={1996}, month={Jul}, pages={5438–5445} }
 @article{faldi_genzer_composto_dozier_1995, title={SEGREGATION AT THE INTERFACE BETWEEN A HOMOPOLYMER AND A BINARY POLYMER BLEND}, volume={74}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.74.3388}, abstractNote={Low-energy forward-recoil spectrometry studies show that the interface between polystyrene ({ital A}) and a miscible blend of two poly(styrene-{ital co}-4-bromostyrene)s ({ital B}:{ital C}) has an interfacial excess of {ital B}, {ital z}{sub {ital B}}{sup *}, where {ital B} is the component with the lower bromostyrene level. At 170 {degree}C, {ital z}{sub {ital B}}{sup *} increases with the bulk volume fraction of {ital B}, {phi}{sub {ital B}{infinity}}, has a maximum near 0.25, and then decreases. These results are in qualitative agreement with self-consistent field (SCF) calculations. SCF calculations of the interfacial tension and interfacial width predict that {ital B} has an optimum compatibilizing effect for {phi}{sub {ital B}{infinity}}{similar_to}0.25.}, number={17}, journal={PHYSICAL REVIEW LETTERS}, author={FALDI, A and GENZER, J and COMPOSTO, RJ and DOZIER, WD}, year={1995}, month={Apr}, pages={3388–3391} }
 @article{genzer_rothman_composto_1994, title={IMPROVED HYDROGEN AND DEUTERIUM DEPTH PROFILING IN POLYMERS USING LOW-ENERGY FORWARD RECOIL SPECTROMETRY}, volume={86}, ISSN={["0168-583X"]}, DOI={10.1016/0168-583x(94)95300-7}, abstractNote={We demonstrate that the hydrogen and deuterium depth resolution of forward recoil spectrometry (FRES) is greatly improved by utilizing 1.3 MeV 4He ions and sample tilting. The near-surface depth resolution is measured on samples of alternating deuterated and protonated polystyrene layers, each ca 250 Å thick. The depth resolution at the surface is dramatically improved (from 800 Å to 250 Å) as the incident beam energy decreases from 3.0 to 1.3 MeV. We call this technique low-energy FRES (LE-FRES) to differentiate it from standard FRES, which uses 3 MeV 4He ions incident at θ = 75°. Furthermore, by using a glancing incident or exit geometry, the LE-FRES depth resolution is improved to ca 125 Å, which is comparable to the resolution of secondary ion mass spectrometry and nuclear reaction analysis. Measurements of the energy and glancing angle dependence of the depth resolution are in quantitative agreement with theoretical predictions. The probing depth of LE-FRES is found to have a maximum at θ ≈ 71° and decreases at glancing exit and incident angles. A contour plot illustrates the relationship between depth resolution and probing depth and provides guidance for future users of LE-FRES.}, number={3-4}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={GENZER, J and ROTHMAN, JB and COMPOSTO, RJ}, year={1994}, month={Apr}, pages={345–354} }
 @article{wallace_zhong_genzer_composto_bonnell_1993, title={ON THE USE OF ION-SCATTERING TO EXAMINE THE ROLE OF HYDROGEN IN THE REDUCTION OF TIO2}, volume={8}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.1993.1629}, abstractNote={Rutherford backscattering spectrometry (RBS) was used to measure the titanium concentration profile for hydrogen-reduced, vacuum-reduced, and as-received, stoichiometric rutile. These profiles give the degree of reduction, specifically, the extent of oxygen deficiency, as a function of depth below the sample surface. Using forward-recoil spectrometry (FRES), the hydrogen-reduced rutile was found to contain more bulk and near-surface hydrogen than the as-received, stoichiometric rutile. This observation provides additional evidence for a hydrogen-diffusion model for the reduction of rutile in a hydrogen environment.}, number={7}, journal={JOURNAL OF MATERIALS RESEARCH}, author={WALLACE, WE and ZHONG, Q and GENZER, J and COMPOSTO, RJ and BONNELL, DA}, year={1993}, month={Jul}, pages={1629–1634} }
 @article{genzer_svorcik_rybka_1990, title={Survey of the reactions of some metals with gallium arsenide applicable in semiconductor technology}, volume={84}, number={11}, journal={Chemicke Listy}, author={Genzer, J. and Svorcik, V. and Rybka, V.}, year={1990}, pages={1146–1160} }