@article{dai_guo_deng_deng_yan_spontak_2023, title={Carbon molecular-sieve membranes developed from a Troger's base polymer and possessing superior gas-separation performance}, volume={680}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2023.121731}, abstractNote={Carbon molecular-sieve membranes possess tremendous practical advantages over unary polymer membranes by providing high gas-separation performance levels, coupled with excellent mechanical and chemical stability. Improving their overall effectiveness greatly expands the competitiveness of this class of membranes. In the present study, carbon membranes are fabricated from a Tröger’s base polymer as the precursor. By optimizing the carbonization conditions, the gas-separation performance of the resultant membranes are significantly enhanced. Under optimized conditions, a H2 permeability of up to 1135 Barrer is achieved, with a corresponding H2/CH4 selectivity of 1170 and a CO2/CH4 selectivity of 238. While increasing the operating temperature slightly reduces the selectivity, it still remains in the high-separation region. Overall, the measured separation performance levels for H2-related separations, i.e., H2/CH4, H2/N2 and H2/CO2, all substantially exceed the Robeson upper bound. Moreover, the CO2/CH4 separation efficacy also lies above the 2019 upper bound, indicating that the carbon membranes developed in the present work are versatile and promising for many different gas-separation applications.}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Dai, Zhongde and Guo, Hongfang and Deng, Jing and Deng, Liyuan and Yan, Jiaqi and Spontak, Richard J.}, year={2023}, month={Aug} }
 @article{yang_germack_spontak_2023, title={Characterization of Controlled-Distribution Hydrogenated Styrenic Block Copolymers by Nuclear Magnetic Resonance Spectroscopy}, volume={7}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.3c00698}, abstractNote={As the need for engineered soft materials continues to grow, block polymers possessing tailored chain architectures and chemical sequences are being upscaled from the laboratory bench to commercial production. Of particular interest here are controlled-distribution styrenic block copolymers (SBCs), i.e., SBCs with the terminal regions adjacent to the monoalkenylarene blocks having a greater than average fraction of conjugated diene units, or one or more regions not adjacent to the monoalkenylarene blocks with a greater than average fraction of monoalkenylarene units. Here, we are specifically interested in applying spectroscopic methods to differentiate their chemical microstructure and derive relevant chemistry-property relationships. In this spirit, we examine the chemical microstructures of fully hydrogenated polystyrene-b-polybutadiene-b-polystyrene and polystyrene-b-poly(styrene-co-butadiene)-b-polystyrene thermoplastic elastomers by a variety of nuclear magnetic resonance (NMR) techniques, including proton (1H) NMR, carbon-13 (13C) NMR, distortionless enhancement by polarization transfer (DEPT) NMR, and heteronuclear single quantum coherence (HSQC) NMR, and cross-correlate the resulting spectra. The impact of styrene in the midblock is clearly discernible from 13C NMR spectra, and precise carbon multiplicity assignments are made on the basis of DEPT NMR and 2D-HSQC NMR results. The information gleaned from 13C NMR, DEPT, and 2D-HSQC NMR spectroscopy provides unambiguous chemical assignments from possible triad and tetrad sequences. High-resolution 13C NMR spectra can thus be used as “fingerprints” to compare the chemical sequencing of different controlled-distribution hydrogenated SBCs and advance the identification of significant sequencing-property relationships in this class of tailored copolymers.}, journal={ACS APPLIED POLYMER MATERIALS}, author={Yang, Jiping and Germack, David S. and Spontak, Richard J.}, year={2023}, month={Jul} }
 @article{wei_deng_ma_qin_wang_deng_spontak_dai_2023, title={High-performance carbon-capture membranes developed by (non)solvent-induced nanostructural rearrangement in Nafion}, volume={8}, ISSN={["2050-7496"]}, DOI={10.1039/d3ta03279e}, abstractNote={Membrane materials exhibiting high CO 2 permeability and selectivity are needed for CO 2 capture to mitigate global climate change.}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Wei, Jing and Deng, Jing and Ma, Yulei and Qin, Zikang and Wang, Bangda and Deng, Liyuan and Spontak, Richard J. J. and Dai, Zhongde}, year={2023}, month={Aug} }
 @article{teran_pal_spontak_lucia_2023, title={Surface Mechanical Properties and Topological Characteristics of Thermoplastic Copolyesters after Precisely Controlled Abrasion}, volume={1}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.2c19377}, DOI={10.1021/acsami.2c19377}, abstractNote={Due to the high probability of surface-to-surface contact of materials during routine applications, surface abrasion remains one of the most challenging factors governing the long-term performance of polymeric materials due to their broad range of tunable mechanical properties, as well as the varied conditions of abrasion (regarding, e.g., rate, load, and contact area). While this concept is empirically mature, a fundamental understanding of mechanical abrasion regarding thermoplastics remains lacking even though polymer abrasion can inadvertently lead to the formation of nano-/microplastics. In the present study, we introduce the concept of precision polymer abrasion (PPA) in conjunction with nanoindentation to elucidate the extent to which controlled wear is experienced by three chemically related thermoplastics under systematically varied abrasion conditions. While depth profiling of one polymer reveals a probe-dependent change in modulus, complementary results from positron annihilation lifetime spectroscopy confirm that the polymer density changes measurably, but not appreciably, with depth over the depth range explored. After a single PPA pass, the surface moduli of the polymers noticeably increase, whereas the corresponding increase in hardness is modest. The dependence of wear volume on the number of PPA passes is observed to reach limiting values for two of the thermoplastics, and application of an empirical model to the data yields estimates of these values for all three thermoplastics. These results suggest that the metrics commonly employed to describe the surface abrasion of polymers requires careful consideration of a host of underlying factors.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Teran, Julio E. and Pal, Lokendra and Spontak, Richard J. and Lucia, Lucian}, year={2023}, month={Jan} }
 @article{sandru_sandru_ingram_deng_stenstad_deng_spontak_2022, title={An integrated materials approach to ultrapermeable and ultraselective CO2 polymer membranes}, volume={376}, ISSN={["1095-9203"]}, DOI={10.1126/science.abj9351}, abstractNote={Advances in membrane technologies that combine greatly improved carbon dioxide (CO2) separation efficacy with low costs, facile fabrication, feasible upscaling, and mechanical robustness are needed to help mitigate global climate change. We introduce a hybrid-integrated membrane strategy wherein a high-permeability thin film is chemically functionalized with a patchy CO2-philic grafted chain surface layer. A high-solubility mechanism enriches the concentration of CO2 in the surface layer hydrated by water vapor naturally present in target gas streams, followed by fast CO2 transport through a highly permeable (but low-selectivity) polymer substrate. Analytical methods confirm the existence of an amine surface layer. Integrated multilayer membranes prepared in this way are not diffusion limited and retain much of their high CO2 permeability, and their CO2 selectivity is concurrently increased in some cases by more than ~150-fold.}, number={6588}, journal={SCIENCE}, author={Sandru, Marius and Sandru, Eugenia M. and Ingram, Wade F. and Deng, Jing and Stenstad, Per M. and Deng, Liyuan and Spontak, Richard J.}, year={2022}, month={Apr}, pages={90-+} }
 @article{jin_khan_spontak_rojas_2021, title={Anion-Specific Water Interactions with Nanochitin: Donnan and Osmotic Pressure Effects as Revealed by Quartz Microgravimetry}, volume={37}, ISSN={["0743-7463"]}, url={https://doi.org/10.1021/acs.langmuir.1c01585}, DOI={10.1021/acs.langmuir.1c01585}, abstractNote={The development of new materials emphasizes greater use of sustainable and eco-friendly resources, including those that take advantage of the unique properties of nanopolysaccharides. Advances in this area, however, necessarily require a thorough understanding of interactions with water. Our contribution to this important topic pertains to the swelling behavior of partially deacetylated nanochitin (NCh), which has been studied here by quartz crystal microgravimetry. Ultrathin films of NCh supported on gold-coated resonators have been equilibrated in aqueous electrolyte solutions (containing NaF, NaCl, NaBr, NaNO3, Na2SO4, Na2SO3, or Na3PO4) at different ionic strengths. As anticipated, NCh displays contrasting swelling/deswelling responses, depending on the ionic affinities and valences of the counterions. The extent of water uptake induced by halide anions, for instance, follows a modified Hofmeister series with F- producing the highest swelling. In marked contrast, Cl- induces film dehydration. We conclude that larger anions promote deswelling such that water losses increase with increasing anion valence. Results such as the ones reported here are critical to ongoing efforts designed to dry chitin nanomaterials and develop bio-based and sustainable materials, including particles, films, coatings, and other nanostructured assemblies, for various devices and applications.}, number={38}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Jin, Soo-Ah and Khan, Saad A. and Spontak, Richard J. and Rojas, Orlando J.}, year={2021}, month={Sep}, pages={11242–11250} }
 @article{jin_facchine_rojas_khan_spontak_2021, title={Cellulose nanofibers and the film-formation dilemma: Drying temperature and tunable optical, mechanical and wetting properties of nanocomposite films composed of waterborne sulfopolyesters}, volume={598}, ISSN={["1095-7103"]}, url={https://doi.org/10.1016/j.jcis.2021.04.032}, DOI={10.1016/j.jcis.2021.04.032}, abstractNote={Waterborne sulfopolyesters have gained considerable interest as coating materials due to their excellent film-forming and optical properties. Their commercial use has been limited, however, due to their fragile nature. Incorporating cellulose nanofiber (CNF), a sustainable biopolymer, into the polymer matrix is expected to enhance the mechanical integrity of the nanocomposite as these two components synergistically interact. In this study, we have investigated the suspension and film characteristics of three sulfopolyesters varying in charge density, glass transition temperature and molecular weight, as well as their mixtures with CNF. We have performed steady-shear rheology on mixtures with different CNF loading levels, and resulting films have been subjected to quasistatic uniaxial tensile and water contact-angle tests to elucidate the effects of CNF on mechanical and surface properties. Addition of CNF to waterborne polyester promotes shear-thinning behavior that remains unaffected by the CNF content. Solid films cast from these suspensions possess enhanced mechanical properties, as well as tailorable surface hydrophilicity, depending on composition and film-drying temperature. Tensile tests reveal that films containing 10 wt% CNF display the greatest mechanical improvements, suggesting the existence of a previously unidentified Goldilocks composition window.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, publisher={Elsevier BV}, author={Jin, Soo-Ah and Facchine, Emily G. and Rojas, Orlando J. and Khan, Saad A. and Spontak, Richard J.}, year={2021}, month={Sep}, pages={369–378} }
 @article{jin_facchine_khan_rojas_spontak_2021, title={Mesophase characteristics of cellulose nanocrystal films prepared from electrolyte suspensions}, volume={599}, ISSN={["1095-7103"]}, url={https://doi.org/10.1016/j.jcis.2021.04.071}, DOI={10.1016/j.jcis.2021.04.071}, abstractNote={Cellulose nanocrystals (CNCs) exhibit a cholesteric mesophase above a critical concentration in aqueous suspensions. Above this concentration, CNCs self-organize into left-handed helicoidal structures that can be preserved in dried, stratified films. In this systematic study, we have prepared optically-active CNC films cast from different electrolyte suspensions and investigated, via circular dichroism and other techniques, the effects of counterion type (six mono/divalent salts, including those responsible for promoting “salting-out” and “salting-in” in the Hofmeister series) and ionic strength on mesomorphic behavior and cholesteric arrangement. The presence of electrolytes influences CNC colloidal stability by compressing the electric double layer and altering interactions among neighboring CNCs and water, thereby affecting the extent to which the CNCs form a mesophase. Interestingly, mesomorphic behavior and CNC alignment appear to be sensitive to cationic radius and charge valence, in which case the optical properties of CNC films can be adjusted for targeted sustainable applications. Such heuristic rules can be valuable for predicting the stability and characteristics of CNC microstructure in designer coatings and thin films prepared by introducing suitable cations prior to film formation.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, publisher={Elsevier BV}, author={Jin, Soo-Ah and Facchine, Emily G. and Khan, Saad A. and Rojas, Orlando J. and Spontak, Richard J.}, year={2021}, month={Oct}, pages={207–218} }
 @article{yan_lee_smith_spontak_2021, title={Morphological Studies of Solution-Crystallized Thermoplastic Elastomers with Polyethylene Endblocks and a Random-Copolymer Midblock}, volume={9}, ISSN={["1521-3927"]}, DOI={10.1002/marc.202100442}, abstractNote={Styrenic thermoplastic elastomers (TPEs) in the form of triblock copolymers possessing glassy endblocks and a rubbery midblock account for the largest global market of TPEs worldwide, and typically rely on microphase separation of the endblocks and the subsequent formation of rigid microdomains to ensure satisfactory network stabilization. In this study, the morphological characteristics of a relatively new family of crystallizable TPEs that instead consist of polyethylene endblocks and a random-copolymer midblock composed of styrene and (ethylene-co-butylene) moieties are investigated. Copolymer solutions prepared at logarithmic concentrations in a slightly endblock-selective solvent are subjected to crystallization under different time and temperature conditions to ascertain if copolymer self-assembly is directed by endblock crystallization or vice versa. According to transmission electron microscopy, semicrystalline aggregates develop at the lowest solution concentration examined (0.01 wt%), and the size and population of crystals, which dominate the copolymer morphologies, are observed to increase with increasing aging time. Real-space results are correlated with small- and wide-angle X-ray scattering to elucidate the concurrent roles of endblock crystallization and self-assembly of these unique TPEs in solution.}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Yan, Jiaqi and Lee, Byeongdu and Smith, Steven D. and Spontak, Richard J.}, year={2021}, month={Sep} }
 @article{peddinti_downs_yan_smith_ghiladi_mhetar_tocchetto_griffiths_scholle_spontak_2021, title={Rapid and Repetitive Inactivation of SARS-CoV-2 and Human Coronavirus on Self-Disinfecting Anionic Polymers}, volume={8}, ISSN={["2198-3844"]}, DOI={10.1002/advs.202003503}, abstractNote={While the ongoing COVID-19 pandemic affirms an urgent global need for effective vaccines as second and third infection waves are spreading worldwide and generating new mutant virus strains, it has also revealed the importance of mitigating the transmission of SARS-CoV-2 through the introduction of restrictive social practices. Here, it is demonstrated that an architecturally- and chemically-diverse family of nanostructured anionic polymers yield a rapid and continuous disinfecting alternative to inactivate coronaviruses and prevent their transmission from contact with contaminated surfaces. Operating on a dramatic pH-drop mechanism along the polymer/pathogen interface, polymers of this archetype inactivate the SARS-CoV-2 virus, as well as a human coronavirus surrogate (HCoV-229E), to the minimum detection limit within minutes. Application of these anionic polymers to frequently touched surfaces in medical, educational, and public-transportation facilities, or personal protection equipment, can provide rapid and repetitive protection without detrimental health or environmental complications.}, number={11}, journal={ADVANCED SCIENCE}, author={Peddinti, Bharadwaja S. T. and Downs, Sierra N. and Yan, Jiaqi and Smith, Steven D. and Ghiladi, Reza A. and Mhetar, Vijay and Tocchetto, Roger and Griffiths, Anthony and Scholle, Frank and Spontak, Richard J.}, year={2021}, month={Jun} }
 @article{ghareeb_peddinti_kisthardt_scholle_spontak_ghiladi_2021, title={Toward Universal Photodynamic Coatings for Infection Control}, volume={8}, ISSN={["2296-858X"]}, DOI={10.3389/fmed.2021.657837}, abstractNote={The dual threats posed by the COVID-19 pandemic and hospital-acquired infections (HAIs) have emphasized the urgent need for self-disinfecting materials for infection control. Despite their highly potent antimicrobial activity, the adoption of photoactive materials to reduce infection transmission in hospitals and related healthcare facilities has been severely hampered by the lack of scalable and cost-effective manufacturing, in which case high-volume production methods for fabricating aPDI-based materials are needed. To address this issue here, we examined the antimicrobial efficacy of a simple bicomponent spray coating composed of the commercially-available UV-photocrosslinkable polymer N -methyl-4(4'-formyl-styryl)pyridinium methosulfate acetal poly(vinyl alcohol) (SbQ-PVA) and one of three aPDI photosensitizers (PSs): zinc-tetra(4- N -methylpyridyl)porphine (ZnTMPyP 4+ ), methylene blue (MB), and Rose Bengal (RB). We applied these photodynamic coatings, collectively termed SbQ-PVA/PS, to a variety of commercially available materials. Scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed the successful application of the coatings, while inductively coupled plasma-optical emission spectroscopy (ICP-OES) revealed a photosensitizer loading of 0.09-0.78 nmol PS/mg material. The antimicrobial efficacy of the coated materials was evaluated against methicillin-susceptible Staphylococcus aureus ATCC-29213 and human coronavirus strain HCoV-229E. Upon illumination with visible light (60 min, 400-700 nm, 65 ± 5 mW/cm 2 ), the coated materials inactivated S. aureus by 97-99.999% and HCoV-229E by 92-99.999%, depending on the material and PS employed. Photobleaching studies employing HCoV-229E demonstrated detection limit inactivation (99.999%) even after exposure for 4 weeks to indoor ambient room lighting. Taken together, these results demonstrate the potential for photodynamic SbQ-PVA/PS coatings to be universally applied to a wide range of materials for effectively reducing pathogen transmission.}, journal={FRONTIERS IN MEDICINE}, author={Ghareeb, C. Roland and Peddinti, Bharadwaja S. T. and Kisthardt, Samantha C. and Scholle, Frank and Spontak, Richard J. and Ghiladi, Reza A.}, year={2021}, month={Jul} }
 @article{armstrong_chatterjee_ghosh_spontak_2020, title={Form-stable phase-change elastomer gels derived from thermoplastic elastomer copolyesters swollen with fatty acids}, volume={686}, ISSN={["1872-762X"]}, url={http://dx.doi.org/10.1016/j.tca.2020.178566}, DOI={10.1016/j.tca.2020.178566}, abstractNote={Phase-change materials (PCMs) are of considerable scientific and technological interest in applications related to energy management and storage, especially as they pertain to residential or commercial construction and packaging. Most PCMs developed for these purposes consist of a crystallizable species encapsulated within an impermeable polymeric shell. Such encapsulants can then be strategically embedded throughout a construct to promote thermal stability in close proximity to the normal melting point of the encapsulated species. In this study, we introduce form-stable PCMs, which avoid the need for costly and inconvenient encapsulation and consist of commercial thermoplastic elastomer copolyesters selectively swollen with crystallizable fatty acids. Since the copolyester matrices endow the PCMs with solid-like characteristics even when swollen with liquid, we refer to this particular class of materials as phase-change elastomer gels (PCEGs). In this study, we explore the thermal characteristics of PCEG films wherein the copolyester grade, gel composition and fatty acid are all varied. Our results indicate that these PCEGs exhibit non-hysteretic thermal cycling, unaffected transition temperatures, and competitive latent transition heats. Relative to model and commercially available encapsulated PCMs, the form-stable PCEGs examined here afford an alternative capable of superior thermal performance and versatility.}, journal={THERMOCHIMICA ACTA}, author={Armstrong, Daniel P. and Chatterjee, Kony and Ghosh, Tushar K. and Spontak, Richard J.}, year={2020}, month={Apr} }
 @article{ito_shiota_taniguchi_spontak_nagai_2020, title={Gas-separation and physical properties of ABA triblock copolymers synthesized from polyimide and hydrophilic adamantane derivatives}, volume={202}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2020.122642}, abstractNote={In this study, ABA triblock copolymers derived from 4,4’-(hexafluoroisopropylidene)-diphthalic anhydride-2,3,5,6-tetramethyl-1,4-phenylenediamine (6FDA-TeMPD; PI) and 3-hydroxy-1-adamantyl methacrylate (HAdMA) or 3,5-dihydroxy-1-adamantyl methacrylate (DHAdMA) have been synthesized via atom transfer radical polymerization to generate mechanically tough and thermally stable gas-separation membranes with composition-tunable transport properties. Due to the inherent thermodynamic incompatibility between the chemically dissimilar blocks, these two series of triblock copolymers appear microphase-separated. While the gas permeability coefficients of these triblock copolymer membranes are consistently lower than that of PI due to the reduced fractional free volume of HAdMA and DHAdMA, the solubility coefficients of the copolymers are higher than that of PI due presumably to specific interactions between the polar hydroxyl group(s) and penetrant gas molecules. These triblock copolymers synthesized from PI and hydrophilic adamantane derivatives constitute a new class of nanostructured polymeric materials possessing excellent thermomechanical properties in conjunction with designer gas-separation properties.}, journal={POLYMER}, author={Ito, Tsubasa and Shiota, Ryunosuke and Taniguchi, Naomi and Spontak, Richard J. and Nagai, Kazukiyo}, year={2020}, month={Aug} }
 @article{janakiram_ansaloni_jin_yu_dai_spontak_deng_2020, title={Humidity-responsive molecular gate-opening mechanism for gas separation in ultraselective nanocellulose/IL hybrid membranes}, volume={22}, ISSN={["1463-9270"]}, DOI={10.1039/d0gc00544d}, abstractNote={A class of “green” hybrid membranes composed of nanocellulose and an ionic liquid exhibits exceptional separation properties arising from a humidity-responsive size-exclusive “gate” that allows selective CO<sub>2</sub> permeation.}, number={11}, journal={GREEN CHEMISTRY}, author={Janakiram, Saravanan and Ansaloni, Luca and Jin, Soo-Ah and Yu, Xinyi and Dai, Zhongde and Spontak, Richard J. and Deng, Liyuan}, year={2020}, month={Jun}, pages={3546–3557} }
 @article{srewaradachpisal_dechwayukul_chatpun_spontak_thongruang_2020, title={Optimization of the Rubber Formulation for Footwear Applications from the Response Surface Method}, volume={12}, ISSN={["2073-4360"]}, DOI={10.3390/polym12092032}, abstractNote={Impact force remains the primary cause of foot injury and general discomfort with regard to footwear. The footwear industry traditionally relies on modified elastomers (including natural rubber) whose properties can be physically adjusted by varying the constituents in the rubber formulations. This work aims to investigate the effect of filler/plasticizer fractions on shock attenuation of natural rubber soles. The statistical response surface method (RSM) was used to optimize the loading of natural rubber, fillers (carbon black and china clay) and a plasticizer (paraffinic oil). A novel predictive equation addressing the effects of additives on the physical and mechanical properties of the shoe sole was successfully created using the RSM. Our results demonstrate how the concentrations of these components regulate final properties, such as impact force absorption and hardness, in the commercial manufacture of shoe soles. While a higher loading level of plasticizer promotes reductions in hardness and impact force, as well as energy dissipation, in these modified elastomers, these properties were improved by increasing the filler content.}, number={9}, journal={POLYMERS}, author={Srewaradachpisal, Satta and Dechwayukul, Charoenyutr and Chatpun, Surapong and Spontak, Richard J. and Thongruang, Wiriya}, year={2020}, month={Sep} }
 @article{peddinti_morales-gagnon_pourdeyhimi_scholle_spontak_ghiladi_2020, title={Photodynamic Coatings on Polymer Microfibers for Pathogen Inactivation: Effects of Application Method and Composition}, volume={13}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/acsami.0c16953}, DOI={10.1021/acsami.0c16953}, abstractNote={A substantial increase in the risk of hospital-acquired infections (HAIs) has greatly impacted the global healthcare industry. Harmful pathogens adhere to a variety of surfaces and infect personnel on contact, thereby promoting transmission to new hosts. This is particularly worrisome in the case of antibiotic-resistant pathogens, which constitute a growing threat to human health worldwide and require new preventative routes of disinfection. In this study, we have incorporated different loading levels of a porphyrin photosensitizer capable of generating reactive singlet oxygen in the presence of O2 and visible light in a water-soluble, photo-cross-linkable polymer coating, which was subsequently deposited on polymer microfibers. Two different application methods are considered, and the morphological and chemical characteristics of these coated fibers are analyzed to detect the presence of the coating and photosensitizer. To discern the efficacy of the fibers against pathogenic bacteria, photodynamic inactivation has been performed on two different bacterial strains, Staphylococcus aureus and antibiotic-resistant Escherichia coli, with population reductions of >99.9999 and 99.6%, respectively, after exposure to visible light for 1 h. In response to the current COVID-19 pandemic, we also confirm that these coated fibers can inactivate a human common cold coronavirus serving as a surrogate for the SARS-CoV-2 virus.}, number={1}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Peddinti, Bharadwaja S. T. and Morales-Gagnon, Nicolas and Pourdeyhimi, Behnam and Scholle, Frank and Spontak, Richard J. and Ghiladi, Reza A.}, year={2020}, month={Dec}, pages={155–163} }
 @article{spontak_ryan_2020, title={Polymer blend compatibilization by the addition of block copolymers}, ISBN={["978-0-12-816006-0"]}, DOI={10.1016/B978-0-12-816006-0.00003-7}, abstractNote={Since most polymer pairs are inherently thermodynamically incompatible, a wide variety of physical methods has been developed to reduce the interfacial tension in, and thus compatibilize, multicomponent polymer blends. In this chapter, we provide an overview of polymer/polymer phase behavior and elucidate the molecular factors responsible for phase separation. Several strategies introduced to compatibilize phase-separated polymer blends are briefly described, with an emphasis on block copolymers as macromolecular surfactants. The unique attributes of neat block copolymers are examined prior to discussing their ubiquitous use as compatibilizing agents in polymer blends. The criteria and conditions capable of promoting compatibilization are consequently identified, and a molecular-level description of the factors responsible for interfacial modification (and adhesion) is provided. In addition to conventional blends prepared by either high-shear melt/solid mixing or solution casting, we further consider compatibilization of blends with precisely controlled and modified interfaces. One example consists of bilayered polymer films that either contain or are separated by block copolymers differing in concentration and/or molecular composition/weight. Similarly, the effectiveness of adding a premade block copolymer to induce compatibilization in phase-modulated bicomponent fibers is also examined.}, journal={COMPATIBILIZATION OF POLYMER BLENDS: MICRO AND NANO SCALE PHASE MORPHOLOGIES, INTERPHASE CHARACTERIZATION, AND PROPERTIES}, author={Spontak, Richard J. and Ryan, Justin J.}, year={2020}, pages={57–102} }
 @article{armstrong_spontak_2019, title={Dielectric and Resistive Heating of Polymeric Media: Toward Remote Thermal Activation of Stimuli-Responsive Soft Materials}, volume={40}, ISSN={["1521-3927"]}, DOI={10.1002/marc.201800669}, abstractNote={Stimuli-responsive soft materials are becoming increasingly important in a wide range of contemporary technologies, and methods by which to promote thermal stimulation remotely are of considerable interest for controllable device deployment, particularly in inaccessible environments such as outer space. Until now, remote thermal stimulation of responsive polymers has relied extensively on the use of nanocomposites wherein embedded nanoparticles/structures are selectively targeted for heating purposes. In this study, an alternative remote-heating mechanism demonstrates that the dielectric and resistive thermal losses introduced upon application of an alternating current generate sufficient heat to raise the temperature of a neat polyimide by over 70 °C within ≈10 s. Thermal imaging is used here to measure current-induced temperature changes of polymeric media, and a proposed analytical model yields predictions that compare reasonably well with experimental data, confirming that such remote heating is viable. Conditions permitting a shape-memory polymer possessing a melting transition and susceptible to dielectric actuation to achieve continuous electrostrain-temperature cycling are identified.}, number={4}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Armstrong, Daniel P. and Spontak, Richard J.}, year={2019}, month={Feb} }
 @article{wozniak-braszak_knitter_markiewicz_ingram_spontak_2019, title={Effect of Composition on the Molecular Dynamics of Biodegradable Isotactic Polypropylene/Thermoplastic Starch Blends}, volume={7}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.9b02774}, abstractNote={Polyolefins such as polypropylene are used in an immensely broad range of commodity products and account for the largest volume of synthetic polymers generated worldwide. For this reason, this family of thermoplastics contributes significantly to solid waste both on land and in the ocean. One viable approach to mitigate this growing problem and simultaneously reduce the cost of and dependence on petroleum-based polymers relies on blends wherein an added biopolymer can promote natural biodegradation. Due to their chemical dissimilarity, however, nonpolar polyolefins and polar biopolymers tend to phase-separate, in which case a fundamental, molecular-level understanding of the role of polymer/polymer interfaces on chain mobility in blends differing in composition is needed. In the present study, the molecular dynamics of blends composed of isotactic polypropylene (iPP) and glycerol-plasticized thermoplastic starch (TPS) are investigated by solid-state proton nuclear magnetic resonance and dielectric relaxat...}, number={19}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Wozniak-Braszak, Aneta and Knitter, Monika and Markiewicz, Ewa and Ingram, Wade F. and Spontak, Richard J.}, year={2019}, month={Oct}, pages={16050–16059} }
 @article{deng_dai_yan_sandru_sandru_spontak_deng_2019, title={Facile and solvent-free fabrication of PEG-based membranes with interpenetrating networks for CO2 separation}, volume={570}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2018.10.031}, abstractNote={For nearly two decades, membranes derived from polyethers have served as promising candidate materials for CO2 separation. Due to the inherent tendency of high-molecular-weight poly(ethylene oxide) (PEO) to crystallize and thus reduce its CO2 permeability, prior studies have focused on membranes produced from low-molecular-weight poly(ethylene glycol) (PEG). In this work, a novel series of cross-linked PEG-based membranes composed of interpenetrating polymer networks has been generated through the use of amine-terminated Jeffamine and multiple acrylate-functionalized cross-linkers in a facile, solvent-free, two-stage reaction. Evidence of cross-linked interpenetrating polymer networks formed by aza-Michael addition and acrylate polymerization is confirmed by real-time fourier-transform infrared spectroscopy. In addition, we systematically investigate the thermal stability, mechanical properties and water sorption of these multicomponent membranes. Corresponding CO2 and N2 transport properties, evaluated by single-gas permeation tests, are found to depend on both the chemical nature of the cross-linkers and the ratio of the interpenetrating networks. Moreover, free PEG dimethyl ether has been added into the optimized cross-linked matrix at different loading levels to further enhance gas-transport properties.}, journal={JOURNAL OF MEMBRANE SCIENCE}, publisher={Elsevier BV}, author={Deng, Jing and Dai, Zhongde and Yan, Jiaqi and Sandru, Marius and Sandru, Eugenia and Spontak, Richard J. and Deng, Liyuan}, year={2019}, month={Jan}, pages={455–463} }
 @article{dai_ansaloni_ryan_spontak_deng_2019, title={Incorporation of an ionic liquid into a midblock-sulfonated multiblock polymer for CO2 capture}, volume={588}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2019.117193}, abstractNote={Abstract In the present work, hybrid block ionomer/ionic liquid (IL) membranes containing up to 40 wt% IL are prepared by incorporating 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF 4 ]) into a midblock-sulfonated pentablock polymer (Nexar) that behaves as a thermoplastic elastomer. Various analytical techniques, including thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, small-angle X-ray scattering (SAXS), and water sorption have been employed to characterize the resultant membrane materials. Single- and mixed-gas permeation tests at different relative humidity conditions have been performed to evaluate membrane gas-separation performance and interrogate the molecular transport of CO 2 through these membranes. Addition of IL to Nexar systematically enhances CO 2 permeability through membranes in the dry state. Introduction of water vapor into the gas feed further promotes CO 2 transport, yielding a maximum permeability of 194 Barrers and a maximum CO 2 /N 2 selectivity of 128 under different test conditions. These results confirm that humidified Nexar/IL hybrid membranes constitute promising candidates for the selective removal, and subsequent capture, of CO 2 from mixed gas streams to reduce the environmental contamination largely responsible for global climate change.}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Dai, Zhongde and Ansaloni, Luca and Ryan, Justin J. and Spontak, Richard J. and Deng, Liyuan}, year={2019}, month={Oct} }
 @article{peddinti_scholle_vargas_smith_ghiladi_spontak_2019, title={Inherently self-sterilizing charged multiblock polymers that kill drug-resistant microbes in minutes}, volume={6}, ISSN={2051-6347 2051-6355}, url={http://dx.doi.org/10.1039/C9MH00726A}, DOI={10.1039/c9mh00726a}, abstractNote={To combat the growing global healthcare threat from drug-resistant pathogens, we demonstrate that midblock-sulfonated block polymers can kill 99.9999% of “superbugs,” including bacteria and viruses, in just 5 minutes due to an abrupt pH reduction.}, number={10}, journal={Materials Horizons}, publisher={Royal Society of Chemistry (RSC)}, author={Peddinti, Bharadwaja S. T. and Scholle, Frank and Vargas, Mariana G. and Smith, Steven D. and Ghiladi, Reza A. and Spontak, Richard J.}, year={2019}, pages={2056–2062} }
 @article{mineart_ryan_appavou_lee_gradzielski_spontak_2019, title={Self-Assembly of a Midblock-Sulfonated Pentablock Copolymer in Mixed Organic Solvents: A Combined SAXS and SANS Analysis}, volume={35}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.8b03825}, abstractNote={Ionic, and specifically sulfonated, block copolymers are continually gaining interest in the soft materials community due to their unique suitability in various ion-exchange applications such as fuel cells, organic photovoltaics, and desalination membranes. One unresolved challenge inherent to these materials is solvent templating, that is, the translation of self-assembled solution structures into nonequilibrium solid film morphologies. Recently, the use of mixed polar/nonpolar organic solvents has been examined in an effort to elucidate and control the solution self-assembly of sulfonated block copolymers. The current study sheds new light on micellar assemblies (i.e., those with the sulfonated blocks comprising the micellar core) of a midblock-sulfonated pentablock copolymer in polar/nonpolar solvent mixtures by combining small-angle X-ray and small-angle neutron scattering. Our scattering data reveal that micelle size depends strongly on overall solvent composition: micelle cores and coronae grow as the fraction of nonpolar solvent is increased. Universal model fits further indicate that an unexpectedly high fraction of the micelle cores is occupied by polar solvent (60–80 vol %) and that partitioning of the polar solvent into micelle cores becomes more pronounced as its overall quantity decreases. This solvent presence in the micelle cores explains the simultaneous core/corona growth, which is otherwise counterintuitive. Our findings provide a potential pathway for the formation of solvent-templated films with more interconnected morphologies due to the greatly solvated micellar cores in solution, thereby enhancing the molecular, ion, and electron-transport properties of the resultant films.}, number={4}, journal={LANGMUIR}, author={Mineart, Kenneth P. and Ryan, Justin J. and Appavou, Marie-Sousai and Lee, Byeongdu and Gradzielski, Michael and Spontak, Richard J.}, year={2019}, month={Jan}, pages={1032–1039} }
 @article{oliver_spontak_manners_2019, title={Solution self-assembly of ABC triblock terpolymers with a central crystallizable poly(ferrocenyldimethylsilane) core-forming segment}, volume={10}, ISBN={1759-9962}, DOI={10.1039/c8py01830h}, abstractNote={The synthesis and solution self-assembly behavior of a range of linear ABC triblock terpolymers with a central crystallizable poly(ferrocenyldimethylsilane) core-forming segment have been explored.}, number={20}, journal={POLYMER CHEMISTRY}, author={Oliver, Alex M. and Spontak, Richard J. and Manners, Ian}, year={2019}, pages={2559–2569} }
 @article{tilly_pervaje_inglefield_santiso_spontak_khan_2019, title={Spectroscopic and Rheological Cross-Analysis of Polyester Polyol Cure Behavior: Role of Polyester Secondary Hydroxyl Content}, volume={4}, ISSN={["2470-1343"]}, url={https://doi.org/10.1021/acsomega.8b02766}, DOI={10.1021/acsomega.8b02766}, abstractNote={The sol-gel transition of a series of polyester polyol resins possessing varied secondary hydroxyl content and reacted with a polymerized aliphatic isocyanate cross-linking agent is studied to elucidate the effect of molecular architecture on cure behavior. Dynamic rheology is utilized in conjunction with time-resolved variable-temperature Fourier-transform infrared spectroscopy to examine the relationship between chemical conversion and microstructural evolution as functions of both time and temperature. The onset of a percolated microstructure is identified for all resins, and apparent activation energies extracted from Arrhenius analyses of gelation and average reaction kinetics are found to depend on the secondary hydroxyl content in the polyester polyols. The similarity between these two activation energies is explored. Gel point suppression is observed in all the resin systems examined, resulting in significant deviations from the classical gelation theory of Flory and Stockmayer. The magnitude of these deviations depends on secondary hydroxyl content, and a qualitative model is proposed to explain the observed phenomena, which are consistent with results previously reported in the literature.}, number={1}, journal={ACS OMEGA}, publisher={American Chemical Society (ACS)}, author={Tilly, Joseph C. and Pervaje, Amulya K. and Inglefield, David L. and Santiso, Erik E. and Spontak, Richard J. and Khan, Saad A.}, year={2019}, month={Jan}, pages={932–939} }
 @article{tuhin_woloszczuk_mineart_pasquinelli_sadler_smith_banaszak_spontak_2018, title={Communication: Molecular-level description of constrained chain topologies in multiblock copolymer gel networks}, volume={148}, ISSN={["1089-7690"]}, url={https://doi.org/10.1063/1.5037231}, DOI={10.1063/1.5037231}, abstractNote={Network characteristics in physical gels composed of solvated block copolymers varying in molecular design are examined here by dynamic rheology and computer simulations. In two triblock copolymer series, one with chain length (N) varied at constant copolymer composition (f) and the other with f varied at constant N, we discern the dependence of equilibrium network metrics on both N and f. Increasing the block number in a linear multiblock series at constant N and f escalates conformational complexity, which dominates network connectivity classified according to a midblock conformation index.}, number={23}, journal={JOURNAL OF CHEMICAL PHYSICS}, publisher={AIP Publishing}, author={Tuhin, Mohammad O. and Woloszczuk, Sebastian and Mineart, Kenneth P. and Pasquinelli, Melissa A. and Sadler, J. David and Smith, Steven D. and Banaszak, Michal and Spontak, Richard J.}, year={2018}, month={Jun} }
 @article{armstrong_spontak_2018, title={Crystallization-Directed Anisotropic Electroactuation in Selectively Solvated Olefinic Thermoplastic Elastomers: A Thermal and (Electro)Mechanical Property Study}, volume={28}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201803467}, abstractNote={Dielectric elastomers (DEs), a class of soft electroactive polymers that change size upon exposure to an external electric field, constitute an increasingly important class of stimuli-responsive polymers due primarily to their large actuation strains, facile and low-cost fabrication, scalability, and mechanical robustness. Unless purposefully constrained, most DEs exhibit isotropic actuation wherein size changes are the same in all actuation directions. Previous studies of DEs containing oriented, stiff fibers have demonstrated, however, that anisotropic actuation along a designated direction is more electromechanically efficient since this design eliminates energy expended in nonessential directions. To identify an alternative, supramolecular-level route to anisotropic electroactuation, we investigate the thermal and mechanical properties of novel thermoplastic elastomer gels composed of a selectively solvated olefinic block copolymer that not only microphase-separates but also crystallizes upon cooling from the solution state. While these materials possess remarkable mechanical attributes (e.g., giant strains in excess of 4000%), their ability to be strain-conditioned enables huge anisotropic actuation levels, measured to be greater than 30 from the ratio of orthogonal actuation strains. This work establishes that crystallization-induced anisotropic actuation can be achieved with these DEs.}, number={36}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Armstrong, Daniel P. and Spontak, Richard J.}, year={2018}, month={Sep} }
 @article{ashraf_ryan_satkowski_smith_spontak_2018, title={Effect of Systematic Hydrogenation on the Phase Behavior and Nanostructural Dimensions of Block Copolymers}, volume={10}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.7b19433}, abstractNote={Unsaturated polydienes are frequently hydrogenated to yield polyolefins that are more chemically stable. Here, the effects of partial hydrogenation on the phase behavior and nanostructure of polyisoprene-containing block copolymers are investigated. To ensure access to the order–disorder transition temperature (TODT) over a wide temperature range, we examine copolymers with at least one random block. Dynamic rheological and scattering measurements indicate that TODT increases linearly with increasing hydrogenation. Small-angle scattering reveals that the temperature-dependence of the Flory–Huggins parameter changes and the microdomain period increases, while the interfacial thickness decreases. The influence of hydrogenation becomes less pronounced in more constrained multiblock copolymers.}, number={4}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ashraf, Arman R. and Ryan, Justin J. and Satkowski, Michael M. and Smith, Steven D. and Spontak, Richard J.}, year={2018}, month={Jan}, pages={3186–3190} }
 @article{cai_mineart_li_spontak_manners_qiu_2018, title={Hierarchical Self-Assembly of Toroidal Micelles into Multidimensional Nanoporous Superstructures}, volume={7}, ISSN={["2161-1653"]}, DOI={10.1021/acsmacrolett.8b00445}, abstractNote={Materials with controlled porosity play a prominent role in industrial and domestic applications. Although a rich array of methods has been developed to tune the pore size over a broad range (from <1 nm to >1 μm), the fabrication of functional materials with a fully open porous structure with sub-100 nm pore size has remained a significant challenge. Herein, we report the hierarchical assembly of block copolymer toroidal micelles with an intrinsic cavity into multidimensional nanoporous superstructures (pore size 85–90 nm) by modulation of interparticle interactions. The toroids aggregate into oligo-supermicelles or 2D hexagonal arrays through van der Waals interactions upon drying on a substrate, while synergistic hydrogen bonding interactions further promote the formation of 3D nanoporous superstructures directly in solution. Thus, toroidal micelles can be manipulated as a type of distinctive building block to construct nanoporous materials.}, number={8}, journal={ACS MACRO LETTERS}, author={Cai, Jiandong and Mineart, Kenneth P. and Li, Xiaoyu and Spontak, Richard J. and Manners, Ian and Qiu, Huibin}, year={2018}, month={Aug}, pages={1040–1045} }
 @article{deng_yan_tilly_deng_mineart_spontak_2018, title={Incorporation of Metallic Species into Midblock-Sulfonated Block Ionomers}, volume={39}, ISSN={["1521-3927"]}, DOI={10.1002/marc.201800427}, abstractNote={Block ionomers can, in the same fashion as their neutral block copolymer analogs, microphase-order into various nanoscale morphologies. The added benefit of a copolymer possessing a charged species is that the resultant block ionomer becomes amphiphilic and capable of imbibing polar liquids, including water. This characteristic facilitates incorporation of metallic species into the soft nanostructure for a wide range of target applications. In this study, the nonpolar and polar constituents of solvent-templated midblock-sulfonated block ionomers (SBIs) are first selectively metallated for complementary morphological analysis. Next, four different salts, with cationic charges ranging from +1 to +3, are introduced into three hydrated SBIs varying in their degree of sulfonation (DOS), and cation uptake is measured as a function of immersion time. These results indicate that uptake generally increases with increasing salt concentration, cationic charge, and specimen DOS. Swelling and nanoindentation measurements conducted at ambient temperature demonstrate that water uptake decreases, while the surface modulus increases, with increasing cationic charge. Chemical spectra acquired from energy-dispersive X-ray spectroscopy (EDS) confirm the presence of each of the ion-exchanged species, and corresponding EDS chemical maps reveal that the spatial distribution of these species is relatively uniform throughout the block ionomer films.}, number={22}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, publisher={Wiley}, author={Deng, Jing and Yan, Jiaqi and Tilly, Joseph C. and Deng, Liyuan and Mineart, Kenneth P. and Spontak, Richard J.}, year={2018}, month={Nov} }
 @article{subramani_spontak_ghosh_2018, title={Influence of fiber characteristics on directed electroactuation of anisotropic dielectric electroactive polymers with tunability}, volume={154}, ISSN={0266-3538}, url={http://dx.doi.org/10.1016/J.COMPSCITECH.2017.11.014}, DOI={10.1016/J.COMPSCITECH.2017.11.014}, abstractNote={Dielectric elastomers constitute a technologically important class of stimuli-responsive polymers due primarily to their unique ability to achieve large strains (>300 area%) upon exposure to an external electric field. In most reported cases, actuation strains are measured as dielectric elastomers constrained to a circular test configuration essentially waste energy by undergoing isotropic, rather than directional, electroactuation. Recent independent studies have demonstrated, however, that the addition of relatively stiff fibers to a soft dielectric elastomer matrix promotes more energy-efficient anisotropic mechanical behavior and electroactuation response. In this work, we investigate the effects of fiber strain and mechanical properties on electroactuation in anisotropic dielectric electroactive polymers with tunability (ADEPT) fabricated from an acrylic dielectric elastomer. Increases in fiber loading level and stiffness are observed to enhance both mechanical and electroactuation properties to different extents, and we introduce an electroactuation anisotropic enhancement factor to quantify the ratio of electroactuation to mechanical anisotropy. This factor is determined to vary linearly with fiber concentration for nearly all the different ADEPT composites examined in this study.}, journal={Composites Science and Technology}, publisher={Elsevier BV}, author={Subramani, Krishna B. and Spontak, Richard J. and Ghosh, Tushar K.}, year={2018}, month={Jan}, pages={187–193} }
 @article{tuhin_ryan_sadler_han_lee_smith_pasquinelli_spontak_2018, title={Microphase-Separated Morphologies and Molecular Network Topologies in Multiblock Copolymer Gels}, volume={51}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ACS.MACROMOL.8B00853}, DOI={10.1021/ACS.MACROMOL.8B00853}, abstractNote={Strong physical gels derived from thermoplastic elastomeric ABA triblock copolymers solvated with a midblock-selective oil continue to find use in increasingly diverse applications requiring highly elastic and mechanically robust soft materials with tunable properties. In this study, we first investigate the morphological characteristics of thermoplastic elastomer gels (TPEGs) derived from a homologous series of linear A(BA)n multiblock copolymers composed of styrene and hydrogenated isoprene repeat units and possessing comparable molecular weight but varying in the number of B-blocks: 1 (triblock), 2 (pentablock), and 3 (heptablock). Small-angle X-ray scattering performed at ambient temperature confirms that (i) increasing hydrogenation reduces the microdomain periodicity of the neat copolymers and (ii) increasing the oil concentration of the TPEGs tends to swell the nanostructure (increasing the periodicity), but concurrently decreases the size of the styrenic micelles, to different extents depending on the molecular architecture. Complementary dissipative particle dynamics simulations reveal the level to which midblock bridging, which is primarily responsible for the elasticity in this class of materials, is influenced by both oil concentration and molecular architecture. Since constrained topological complexity increases with increasing block number, we introduce a midblock conformation index that facilitates systematic classification of the different topologies involved in nearest-micelle bridge formation. Those possessing at least one bridged and one looped midblock with no dangling ends are found to be the most predominant topologies in the pentablock and heptablock networks.}, number={14}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Tuhin, Mohammad O. and Ryan, Justin J. and Sadler, J. David and Han, Zexiang and Lee, Byeongdu and Smith, Steven D. and Pasquinelli, Melissa A. and Spontak, Richard J.}, year={2018}, month={Jul}, pages={5173–5181} }
 @article{pervaje_tilly_inglefield_spontak_khan_santiso_2018, title={Modeling Polymer Glass Transition Properties from Empirical Monomer Data with the SAFT-gamma Mie Force Field}, volume={51}, DOI={10.1021/acs.macromol.8b01734}, abstractNote={We apply a recently developed coarse-graining method to build models for polyester polyols, versatile polymers with applications in coatings, by combining models for the component monomers. This strategy employs the corresponding states correlation to the group-contribution SAFT-γ Mie equation of state [Mejia, A.; et al. Ind. Eng. Chem. Res. 2014, 53, 4131–4141] to obtain force-field parameters for the constituent monomer species. Results from simulations agree favorably with experimental values of mass density, glass transition temperature (Tg), and specific heat capacity change at Tg. Further simulations over a range of Mie parameters and polymer chemical compositions yield a correlation that relates the parameters directly to Tg. This correlation is validated by experimental data and can be used as a predictive tool within the tested parameter space to expedite the design of these coating materials.}, number={23}, journal={MACROMOLECULES}, author={Pervaje, Amulya K. and Tilly, Joseph C. and Inglefield, David L. and Spontak, Richard and Khan, Saad and Santiso, Erik E.}, year={2018}, pages={9526–9537} }
 @article{dai_ansaloni_ryan_spontak_deng_2018, title={Nafion/IL hybrid membranes with tuned nanostructure for enhanced CO2 separation: effects of ionic liquid and water vapor}, volume={20}, ISSN={["1463-9270"]}, DOI={10.1039/c7gc03727a}, abstractNote={Fully hydrated hybrid membranes based on a polyelectrolyte mixed with an ionic liquid possess gas permeation properties of significant interest for CO<sub>2</sub> capture applications.}, number={6}, journal={GREEN CHEMISTRY}, author={Dai, Zhongde and Ansaloni, Luca and Ryan, Justin J. and Spontak, Richard J. and Deng, Liyuan}, year={2018}, month={Mar}, pages={1391–1404} }
 @article{ryan_mineart_lee_spontak_2018, title={Ordering and Grain Growth in Charged Block Copolymer Bulk Films: A Comparison of Solvent-Related Processes}, volume={5}, ISSN={["2196-7350"]}, DOI={10.1002/admi.201701667}, abstractNote={Abstract While prior efforts have demonstrated that the morphologies of block copolymer (BC) bulk films can be controlled through judicious chemical design and thermal annealing, recent interest has focused on regulating the orientation of BC nanostructures and minimizing defects. Thermal processes developed to achieve this purpose for nonpolar BCs are not, however, suitable for orienting microphase‐ordered BCs composed of at least one block with charged moieties that can form thermally stable ionic clusters. To overcome this challenge, we have previously applied solvent‐vapor (SV) annealing to block ionomer (BI) bulk films composed of midblock‐sulfonated pentablock copolymers and established that this approach yields highly ordered morphologies that display evidence of improved in‐plane orientation. Here, we employ small‐angle X‐ray scattering to compare the effectiveness of three solvent‐related processes–SV annealing, SV permeation, and SV sorption–on BI ordering and grain growth, and offer explanations for observed differences on the basis of thermodynamic‐ and transport‐related considerations. Differences in the experimental design of these solvent‐related processes are found to affect nanostructural development, as evidenced by the extent of in‐plane grain growth.}, number={8}, journal={ADVANCED MATERIALS INTERFACES}, author={Ryan, Justin J. and Mineart, Kenneth P. and Lee, Byeongdu and Spontak, Richard J.}, year={2018}, month={Apr} }
 @article{peddinti_scholle_ghiladi_spontak_2018, title={Photodynamic Polymers as Comprehensive Anti-Infective Materials: Staying Ahead of a Growing Global Threat}, volume={10}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/ACSAMI.8B09139}, DOI={10.1021/ACSAMI.8B09139}, abstractNote={To combat the global threat posed by surface-adhering pathogens that are becoming increasingly drug-resistant, we explore the anti-infective efficacy of bulk thermoplastic elastomer films containing ∼1 wt % zinc-tetra(4-N-methylpyridyl)porphine (ZnTMPyP4+), a photoactive antimicrobial that utilizes visible light to generate singlet oxygen. This photodynamic polymer is capable of inactivating five bacterial strains and two viruses with at least 99.89% and 99.95% success, respectively, after exposure to noncoherent light for 60 min. Unlike other anti-infective methodologies commonly requiring oxidizing chemicals, carcinogenic radiation, or toxic nanoparticles, our approach is nonspecific and safe/nontoxic, and sustainably relies on the availability of just oxygen and visible light.}, number={31}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Peddinti, Bharadwaja S.T. and Scholle, Frank and Ghiladi, Reza A. and Spontak, Richard J.}, year={2018}, month={Jul}, pages={25955–25959} }
 @article{torstensen_johnsen_riis_spontak_deng_gregersen_syverud_2018, title={Preparation of cellulose nanofibrils for imaging purposes: comparison of liquid cryogens for rapid vitrification}, volume={25}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-018-1854-8}, abstractNote={Artifact-free imaging of cellulose nanofibrils (CNFs) from aqueous nanocellulose suspensions is nontrivial due to frequent irreversible agglomeration and structure damage during the course of sample preparation, especially as water is solidified prior to freeze-drying. In this study, we have examined the morphologies of CNF suspensions prepared by rapid vitrification in two different liquid cryogens—nitrogen and ethane—followed by freeze-drying. Results obtained by scanning electron microscopy confirm that vitrification in liquid ethane not only greatly improves the survivability of fine-scale CNF structural elements but also significantly reduces the propensity for CNF to agglomerate.}, number={8}, journal={CELLULOSE}, author={Torstensen, Jonathan O. and Johnsen, Per-Olav and Riis, Henrik and Spontak, Richard J. and Deng, Liyuan and Gregersen, Oyvind W. and Syverud, Kristin}, year={2018}, month={Aug}, pages={4269–4274} }
 @article{al-mohsin_mineart_armstrong_el-shafei_spontak_2018, title={Quasi-Solid-State Dye-Sensitized Solar Cells Containing a Charged Thermoplastic Elastomeric Gel Electrolyte and Hydrophilic/phobic Photosensitizers}, volume={2}, ISSN={2367-198X}, url={http://dx.doi.org/10.1002/SOLR.201700145}, DOI={10.1002/SOLR.201700145}, abstractNote={As the threat of global climate change due to combustion emissions becomes increasingly alarming, the search for clean and sustainable alternative energy is of paramount importance. With this objective in mind, harnessing solar energy is particularly attractive due to ongoing improvements in silicon-, perovskite-, and organic-based solar cells. Of these, dye-sensitized solar cells (DSSCs) constitute a promising technology due to their relatively low cost, moderate conversion efficiency, and robust mechanical properties. An important breakthrough in the development of DSSCs is the use of polymer gel electrolytes. In this work, we employ amphi­philic thermoplastic elastomers (TPEs) in the form of sulfonated block ionomer (SBI) homologs for this purpose. Since the midblock of each charged copolymer is hydrophilic, the resultant microphase-separated nanostructures consist of continuous ionic channels that facilitate electron diffusion. A unique characteristic of the SBI archetype studied here is that the morphology can be solvent-templated. We exploit this feature by introducing either hydrophilic or hydrophobic photosensitizers into the DSSCs. When the SBI exhibits a primarily lamellar morphology, a hydrophilic dye yields the highest efficiency (7.0%), whereas the opposite is observed when the nanostructure consists of a solvent-templated nonpolar matrix. Photosensi­tizer tunability is augmented by the intrinsic mechanical and adhesive properties of a TPE.}, number={3}, journal={Solar RRL}, publisher={Wiley}, author={Al-Mohsin, Heba A. and Mineart, Kenneth P. and Armstrong, Daniel P. and El-Shafei, Ahmed and Spontak, Richard J.}, year={2018}, month={Jan}, pages={1700145} }
 @article{al-mohsin_mineart_armstrong_el-shafei_spontak_2018, title={Quasi-solid-state dye-sensitized solar cells containing a charged thermoplastic elastomeric gel electrolyte and hydrophilic/phobic photosensitizers}, volume={2}, DOI={10.1002/solr.201770155}, number={3}, journal={Solar RRL}, author={Al-Mohsin, H. A. and Mineart, K. P. and Armstrong, D. P. and El-Shafei, Ahmed and Spontak, Richard}, year={2018} }
 @article{torstensen_liu_jin_deng_hawari_syverud_spontak_gregersen_2018, title={Swelling and Free-Volume Characteristics of TEMPO-Oxidized Cellulose Nanofibril Films}, volume={19}, ISSN={["1526-4602"]}, DOI={10.1021/acs.biomac.7b01814}, abstractNote={Cellulose nanofibrils (CNFs) are becoming increasingly ubiquitous in diverse technologies requiring sustainable nanoscale species to form or modify films. The objective of the present study is to investigate the swelling behavior and accompanying free volume of self-standing TEMPO-oxidized (TO) CNF films in the presence of water vapor. For this purpose, we have performed time-resolved swelling experiments on films, prepared according to different experimental protocols, at 90% relative humidity (RH) and ambient temperature. Corresponding free-volume characteristics are elucidated by positron annihilation lifetime spectroscopy (PALS) conducted at ambient temperature and several RH levels. Increasing the drying temperature of the films (from ambient to 50 °C) is observed to promote an increase in film density, which serves to reduce bulk swelling. These elevated drying temperatures likewise cause the free-volume pore size measured by PALS to decrease, while the corresponding total free-volume fraction remains nearly constant. Similarly, dispersion of TO-CNF into aqueous suspensions by ultrasonication prior to film formation increases both the total free-volume fraction and pore size but reduces the size of individual nanofibrils with little net change in bulk swelling. The swelling and concurrent free-volume measurements reported here generally reveal an increase in the free volume of TO-CNF films with increasing RH.}, number={3}, journal={BIOMACROMOLECULES}, author={Torstensen, Jonathan O. and Liu, Ming and Jin, Soo-Ah and Deng, Liyuan and Hawari, Ayman I. and Syverud, Kristin and Spontak, Richard J. and Gregersen, Oyvind W.}, year={2018}, month={Mar}, pages={1016–1025} }
 @article{turgut_tuhin_toprakci_pasquinelli_spontak_toprakci_2018, title={Thermoplastic Elastomer Systems Containing Carbon Nanofibers as Soft Piezoresistive Sensors}, volume={3}, ISSN={["2470-1343"]}, DOI={10.1021/acsomega.8b01740}, abstractNote={Soft, wearable or printable strain sensors derived from conductive polymer nanocomposites (CPNs) are becoming increasingly ubiquitous in personal-care applications. Common elastomers employed in the fabrication of such piezoresistive CPNs frequently rely on chemically cross-linked polydiene or polysiloxane chemistry, thereby generating relatively inexpensive and reliable sensors that become solid waste upon application termination. Moreover, the shape anisotropy of the incorporated conductive nanoparticles can produce interesting electrical effects due to strain-induced spatial rearrangement. In this study, we investigate the morphological, mechanical, electrical, and electromechanical properties of CPNs generated from thermoplastic elastomer (TPE) triblock copolymer systems containing vapor-grown carbon nanofiber (CNF). Modulus-tunable TPE gels imbibed with a midblock-selective aliphatic oil exhibit well-behaved properties with increasing CNF content, but generally display nonlinear negative piezoresistance at different strain amplitudes and stretch rates due to nanofiber mobility upon CPN strain-cycling. In contrast, a neat TPE possessing low hard-block content yields a distinctive strain-reversible piezoresistive response, as well as low electrical hysteresis, upon cyclic deformation. Unlike their chemically cross-linked analogs, these physically cross-linked and thus environmentally benign CPNs are fully reprocessable by thermal and/or solvent means.}, number={10}, journal={ACS OMEGA}, author={Turgut, Ayse and Tuhin, Mohammad O. and Toprakci, Ozan and Pasquinelli, Melissa A. and Spontak, Richard J. and Toprakci, Hatice A. K.}, year={2018}, month={Oct}, pages={12648–12657} }
 @article{an_huang_mineart_dong_spontak_gubbins_2017, title={Adhesion and friction in polymer films on solid substrates: conformal sites analysis and corresponding surface measurements}, volume={13}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/C7SM00261K}, DOI={10.1039/c7sm00261k}, abstractNote={In this work, we present a statistical mechanical analysis to elucidate the molecular-level factors responsible for the static and dynamic properties of polymer films. This analysis, which we term conformal sites theory, establishes that three dimensionless parameters play important roles in determining differences from bulk behavior for thin polymer films near to surfaces: a microscopic wetting parameter, αwx, defined as the ratio of polymer–substrate interaction to polymer–polymer interaction; a dimensionless film thickness, H*; and dimensionless temperature, T*. The parameter αwx introduced here provides a more fundamental measure of wetting than previous metrics, since it is defined in terms of intermolecular forces and the atomic structure of the substrate, and so is valid at the nanoscale for gas, liquid or solid films. To test this theoretical analysis, we also report atomic force microscopy measurements of the friction coefficient (μ), adhesion force (FA) and glass transition temperature (Tg) for thin films of two polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), on two planar substrates, graphite and silica. Both the friction coefficient and the glass transition temperature are found to increase as the film thickness decreases, and this increase is more pronounced for the graphite than for the silica surface. The adhesion force is also greater for the graphite surface. The larger effects encountered for the graphite surface are attributed to the fact that the microscopic wetting parameter, αwx, is larger for graphite than for silica, indicating stronger attraction of polymer chains to the graphite surface.}, number={19}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={An, Rong and Huang, Liangliang and Mineart, Kenneth P. and Dong, Yihui and Spontak, Richard J. and Gubbins, Keith E.}, year={2017}, pages={3492–3505} }
 @article{ashraf_ryan_satkowski_lee_smith_spontak_2017, title={Bicomponent Block Copolymers Derived from One or More Random Copolymers as an Alternative Route to Controllable Phase Behavior}, volume={38}, ISSN={["1521-3927"]}, DOI={10.1002/marc.201700207}, abstractNote={Block copolymers have been extensively studied due to their ability to spontaneously self-organize into a wide variety of morphologies that are valuable in energy-, medical-, and conservation-related (nano)technologies. While the phase behavior of bicomponent diblock and triblock copolymers is conventionally governed by temperature and individual block masses, it is demonstrated here that their phase behavior can alternatively be controlled through the use of blocks with random monomer sequencing. Block random copolymers (BRCs), i.e., diblock copolymers wherein one or both blocks are a random copolymer comprised of A and B repeat units, have been synthesized, and their phase behavior, expressed in terms of the order–disorder transition (ODT), has been investigated. The results establish that, depending on the block composition contrast and molecular weight, BRCs can microphase-separate. We also report that large variation in incompatibility can be generated at relatively constant molecular weight and temperature with these new soft materials. This sequence-controlled synthetic strategy is extended to thermoplastic elastomeric triblock copolymers differing in chemistry and possessing a random-copolymer midblock.}, number={17}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Ashraf, Arman R. and Ryan, Justin J. and Satkowski, Michael M. and Lee, Byeongdu and Smith, Steven D. and Spontak, Richard J.}, year={2017}, month={Sep} }
 @article{vatankhah-varnoosfaderani_daniel_zhushma_li_morgan_matyjaszewski_armstrong_spontak_dobrynin_sheiko_et al._2017, title={Bottlebrush Elastomers: A New Platform for Freestanding Electroactuation}, volume={29}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201604209}, abstractNote={Freestanding, single-component dielectric actuators are designed based on bottlebrush elastomers that enable giant reversible strokes at relatively low electric fields and altogether avoid preactuation mechanical manipulation. This materials design platform allows for independent tuning of actuator rigidity and elasticity over broad ranges without changing chemical composition, which opens new opportunities in soft-matter robotics.}, number={2}, journal={ADVANCED MATERIALS}, author={Vatankhah-Varnoosfaderani, M. and Daniel, W. F. M. and Zhushma, A. P. and Li, Q. X. and Morgan, B. J. and Matyjaszewski, K. and Armstrong, D. P. and Spontak, Richard and Dobrynin, A. V. and Sheiko, S. S. and et al.}, year={2017}, month={Jan} }
 @article{vatankhah-varnosfaderani_daniel_zhushma_li_morgan_matyjaszewski_armstrong_dobrynin_sheyko_spontak_et al._2017, title={Bottlebrush elastomers: a promising molecular engineering route to tunable, prestrain-free dielectric elastomers (Conference Presentation)}, volume={10163}, ISBN={["978-1-5106-0812-2"]}, ISSN={["0277-786X"]}, DOI={10.1117/12.2261913}, abstractNote={Electroactive polymers (EAPs) refer to a broad range of relatively soft materials that change size and/or shape upon application of an electrical stimulus. Of these, dielectric elastomers (DEs) generated from either chemically- or physically-crosslinked polymer networks afford the highest levels of electroactuation strain, thereby making this class of EAPs the leading technology for artificial-muscle applications. While mechanically prestraining elastic networks remarkably enhances DEs electroactuation, external prestrain protocols severely limit both actuator performance and device implementation due to gradual DE stress relaxation and the presence of a cumbersome load frame. These drawbacks have persisted with surprisingly minimal advances in the actuation of single-component elastomers since the dawn of the “pre-strain era” introduced by Pelrine et al. (Science, 2000). In this work, we present a bottom-up, molecular-based strategy for the design of prestrain-free (freestanding) DEs derived from covalently-crosslinked bottlebrush polymers. This architecture, wherein design factors such as crosslink density, graft density and graft length can all be independently controlled, yields inherently strained polymer networks that can be readily adapted to a variety of chemistries. To validate the use of these molecularly-tunable materials as DEs, we have synthesized a series of bottlebrush silicone elastomers in as-cast shapes. Examination of these materials reveals that they undergo giant electroactuation strains (>300%) at relatively low fields (<10 V/m), thereby outperforming all commercial DEs to date and opening new opportunities in responsive soft-material technologies (e.g., robotics). The molecular design approach to controlling (electro)mechanical developed here is independent of chemistry and permits access to an unprecedented range of actuation properties from elastomeric materials with traditionally modest electroactuation performance (e.g., polydimethylsiloxane, PDMS). Experimental results obtained here compare favorably with theoretical predictions and demonstrate that the unique behavior of these materials is a direct consequence of the molecular architecture.}, journal={ELECTROACTIVE POLYMER ACTUATORS AND DEVICES (EAPAD) 2017}, author={Vatankhah-Varnosfaderani, M. and Daniel, W. F. M. and Zhushma, A. P. and Li, Q. X. and Morgan, B. J. and Matyjaszewski, K. and Armstrong, D. P. and Dobrynin, A. V. and Sheyko, S. S. and Spontak, Richard and et al.}, year={2017} }
 @article{woloszczuk_tuhin_gade_pasquinelli_banaszak_spontak_2017, title={Complex Phase Behavior and Network Characteristics of Midblock-Solvated Triblock Copolymers as Physically Cross-Linked Soft Materials}, volume={9}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.7b14298}, abstractNote={In the presence of a midblock-selective solvent, triblock copolymers not only self-organize but also form a molecular network. Thermoplastic elastomer gels constitute examples of such materials and serve as sealants and adhesives, as well as ballistic, microfluidic, and electroactive media. We perform Monte Carlo and dissipative particle dynamics simulations to investigate the phase behavior and network characteristics of these materials. Of particular interest is the existence of a truncated octahedral morphology that resembles the atomic arrangement of various inorganic species. Both simulation approaches quantify the midblock bridges responsible for network development and thus provide a detailed molecular picture of these composition-tunable soft materials.}, number={46}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Woloszczuk, Sebastian and Tuhin, Mohammad O. and Gade, Soumya R. and Pasquinelli, Melissa A. and Banaszak, Michal and Spontak, Richard J.}, year={2017}, month={Nov}, pages={39940–39944} }
 @article{armstrong_spontak_2017, title={DESIGNING DIELECTRIC ELASTOMERS OVER MULTIPLE LENGTH SCALES FOR 21ST CENTURY SOFT MATERIALS TECHNOLOGIES}, volume={90}, ISSN={["1943-4804"]}, DOI={10.5254/rct.17.82660}, abstractNote={ABSTRACT Dielectric elastomers (DEs) constitute an increasingly important category of electroactive polymers. They are in a class of generally soft materials that, upon exposure to an electric stimulus, respond by changing size, shape, or both. Derived from network-forming macromolecules, DEs are lightweight, robust and scalable, and they are capable of exhibiting giant electroactuation strains, high electromechanical efficiencies, and relatively low strain-cycling hysteresis over a broad range of electric fields. Due primarily to their attractive electromechanical attributes, DEs are of growing interest in diverse biomedical, (micro)robotic, and analytical technologies. Since the seminal studies of these electroresponsive materials (initially fabricated mainly from chemically cross-linked acrylic and silicone elastomers), advances in materials design over multiple length scales have resulted in not only improved electromechanical performance but also better mechanistic understanding. We first review the fundamental operating principles of DEs developed from conventional elastomers that undergo isotropic electroactuation and then consider more recent advances at different length scales. At the macroscale, incorporation of oriented fibers within elastomeric matrices is found to have a profound impact on electroactuation by promoting an anisotropic response. At the mesoscale, physically cross-linked thermoplastic elastomer gel networks formed by midblock-swollen triblock copolymers provide a highly tunable alternative to chemically cross-linked elastomers. At the nanoscale, the chemical synthesis of binetwork and bottlebrush elastomers permits extraordinarily enhanced electromechanical performance through targeted integration of inherently prestrained macromolecular networks.}, number={2}, journal={RUBBER CHEMISTRY AND TECHNOLOGY}, author={Armstrong, Daniel P. and Spontak, Richard J.}, year={2017}, pages={207–224} }
 @article{soltani_smith_spontak_2017, title={Effect of polyelectrolyte on the barrier efficacy of layer-by-layer nanoclay coatings}, volume={526}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2016.12.022}, abstractNote={The development of effective barrier materials is becoming increasingly important, particularly as microelectronic devices and food supplies must be protected for extended periods of time from atmospheric gases and water vapor. One of the most effective, facile, eco-friendly, and inexpensive strategies introduced in this spirit is the sequential buildup of layer-by-layer (LBL) surface coatings. This technology relies on the repeated, alternating deposition of impermeable nanoclay platelets possessing a large diameter-to-thickness aspect ratio and a polyelectrolyte adhesive. Previous studies have focused extensively on the use of polycations for this purpose since they are attracted by the negative charges inherently present on the face of natural nanoclays, such as montmorillonite (MMT). In this work, we compare the barrier properties of LBL coatings prepared with a common polycation and a polyester-based polyanion, which selectively interacts with the positive charges that accumulate on the edges of nanoclay platelets. Deposition of these coatings on a hydrophobic styrenic copolymer is reported here to promote dramatic reductions in the measured permeabilities of oxygen and carbon dioxide. This study, which systematically explores the dependence of single-gas permeability on factors such as MMT suspension concentration, bilayer (BL) coating number and temperature, aims to expand the understanding of LBL coatings by also elucidating morphological considerations.}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Soltani, Iman and Smith, Steven D. and Spontak, Richard J.}, year={2017}, month={Mar}, pages={172–180} }
 @article{mineart_dickerson_love_lee_zuo_spontak_2017, title={Hydrothermal Conditioning of Physical Hydrogels Prepared from a Midblock-Sulfonated Multiblock Copolymer}, volume={38}, ISSN={["1521-3927"]}, DOI={10.1002/marc.201600666}, abstractNote={Since nanostructured amphiphilic macromolecules capable of affording high ion and water transport are becoming increasingly important in a wide range of contemporary energy and environmental technologies, the swelling kinetics and temperature dependence of water uptake are investigated in a series of midblock-sulfonated thermoplastic elastomers. Upon self-assembly, these materials maintain a stable hydrogel network in the presence of a polar liquid. In this study, real-time water-sorption kinetics in copolymer films prepared by different casting solvents are elucidated by synchrotron small-angle X-ray scattering and gravimetric measurements, which directly correlate nanostructural changes with macroscopic swelling to establish fundamental structure-property behavior. By monitoring the equilibrium swelling capacity of these materials over a range of temperatures, an unexpected transition in the vicinity of 50 °C has been discovered. Depending on copolymer morphology and degree of sulfonation, hydrothermal conditioning of specimens to temperatures above this transition permits retention of superabsorbent swelling at ambient temperature.}, number={5}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Mineart, Kenneth P. and Dickerson, Joshua D. and Love, Dillon M. and Lee, Byeongdu and Zuo, Xiaobing and Spontak, Richard J.}, year={2017}, month={Mar} }
 @article{vatankhah-varnosfaderani_sheyko_matyjaszewski_daniel_li_morgan_spontak_2017, title={Inherently pre-strained elastomers with self-healing property: new generation of freestanding electroactuators (Conference Presentation)}, volume={10163}, ISBN={["978-1-5106-0812-2"]}, ISSN={["0277-786X"]}, DOI={10.1117/12.2261503}, abstractNote={Dielectric elastomers (DEs) are the leading technology for artificial muscles due to a favorable combination of large stroke, fast response, and high energy density. However, at large actuations, DEs are prone to spontaneous rupture from electromechanical instability. This shortcoming is currently circumvented by chemical or physical bracing, which increases bulk and rigidity of the total actuator assembly and leads to significant cutbacks in device efficiency and utility. Now, we present a molecular design platform for the creation of freestanding actuators that allow for large stroke (>300%) at low applied fields (<10 V &mu;m-1) in unconstrained as cast shapes. This approach is based on bottlebrush architecture, which features inherently strained polymer networks that eliminate electromechanical instability and the need for bracing. Through accurate control of side-chain length and crosslink density, we obtained effective actuation properties on par with commercial actuators with the advantage of lighter weight, lower voltage operation, and ease of fabrication, which open new opportunities in soft-matter robotics. Furthermore, incorporation of dynamic reversible bonds ensures self-healing of rupture actuators.}, journal={ELECTROACTIVE POLYMER ACTUATORS AND DEVICES (EAPAD) 2017}, author={Vatankhah-Varnosfaderani, Mohammad and Sheyko, Sergei S. and Matyjaszewski, Krzysztof and Daniel, William F. M. and Li, Qiaoxi and Morgan, Benjamin J. and Spontak, Richard J.}, year={2017} }
 @article{ashraf_ryan_satkowski_lee_smith_spontak_2017, title={Macromol. Rapid Commun. 17/2017}, volume={38}, ISSN={1022-1336}, url={http://dx.doi.org/10.1002/MARC.201770055}, DOI={10.1002/MARC.201770055}, abstractNote={Front Cover: Controlling the ability of block copolymers to microphase-order is generally achieved through a judicious combination of temperature, molecular weight, and composition. In article number 1700207, Steven D. Smith, Richard J. Spontak, and co-workers demonstrate that the incorporation of one or more random copolymers as blocks provides an independent route by which to tune the phase behavior of bicomponent diblock and triblock copolymers.}, number={17}, journal={Macromolecular Rapid Communications}, publisher={Wiley}, author={Ashraf, Arman R. and Ryan, Justin J. and Satkowski, Michael M. and Lee, Byeongdu and Smith, Steven D. and Spontak, Richard J.}, year={2017}, month={Sep} }
 @article{dobies_makrocka-rydzyk_jenczykt_jarek_spontak_jurga_2017, title={Molecular Dynamics Study of Polystyrene-b-poly(ethylene oxide) Asymmetric Diblock Copolymer Systems}, volume={33}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.7b02017}, abstractNote={Two polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers differing in molecular mass (49 and 78 kDa) but possessing the same PEO cylindrical morphology are examined to elucidate their molecular dynamics. Of particular interest here is the molecular motion of the PEO blocks involved in the rigid amorphous fraction (RAF). An analysis of complementary thermal calorimetry and X-ray scattering data confirms the presence of microphase-separated morphology as well as semicrystalline structure in each copolymer. Molecular motion within the copolymer systems is monitored by dielectric and nuclear magnetic resonance spectroscopies. The results reported herein reveal the existence of two local Arrhenius-type processes attributed to the noncooperative local motion of PEO segments involved in fully amorphous and rigid amorphous PEO microphases. In both systems, two structural relaxations governed by glass-transition phenomena are identified and assigned to cooperative segmental motion in the fully amorphous phase (the α process) and the RAF (the αc process). We measure the temperature dependence of the dynamics associated with all of the processes mentioned above and propose that these local processes are associated with corresponding cooperative segmental motion in both copolymer systems. In marked contrast to the thermal activation of the α process as discerned in both copolymers, the αc process appears to be a sensitive probe of the copolymer nanostructure. That is, the copolymer with shorter PEO blocks exhibits more highly restricted cooperative dynamics of PEO segments in the RAF, which can be explained in terms of the greater constraint imposed by the glassy PS matrix on the PEO blocks comprising smaller cylindrical microdomains.}, number={36}, journal={LANGMUIR}, author={Dobies, M. and Makrocka-Rydzyk, M. and Jenczykt, J. and Jarek, M. and Spontak, R. J. and Jurga, S.}, year={2017}, month={Sep}, pages={8856–8868} }
 @article{mineart_ryan_lee_smith_spontak_2017, title={Molecular and Morphological Characterization of Midblock-Sulfonated Styrenic Triblock Copolymers}, volume={55}, ISSN={["1099-0488"]}, DOI={10.1002/polb.24294}, abstractNote={Midblock-sulfonated triblock copolymers afford a desirable opportunity to generate network-forming amphiphilic materials that are suitable for use in a wide range of emerging technologies as fuel-cell, water-desalination, ion-exchange, photovoltaic, or electroactive membranes. Employing a previously reported synthetic strategy wherein poly(p-tert-butylstyrene) remains unreactive, we have selectively sulfonated the styrenic midblock of a poly(p-tert-butylstyrene-b-styrene-b-p-tert-butylstyrene) (TST) triblock copolymer to different extents. Comparison of the resulting sulfonated copolymers with results from our prior study provides favorable quantitative agreement and suggests that a shortened reaction time is advantageous. An ongoing challenge regarding the morphological development of charged block copolymers is the competition between microphase separation of the incompatible blocks and physical cross-linking of ionic clusters, with the latter often hindering the former. Here, we expose the sulfonated TST copolymers to solvent-vapor annealing to promote nanostructural refinement. The effect of such annealing on morphological characteristics, as well as on molecular free volume, is explored. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 490–497}, number={6}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Mineart, Kenneth P. and Ryan, Justin J. and Lee, Byeongdu and Smith, Steven D. and Spontak, Richard J.}, year={2017}, month={Mar}, pages={490–497} }
 @article{caydamli_yildirim_shen_fang_pasquinelli_spontak_tonelli_2017, title={Nanoscale considerations responsible for diverse macroscopic phase behavior in monosubstituted isobutyl-POSS/poly(ethylene oxide) blends}, volume={13}, ISSN={["1744-6848"]}, url={https://doi.org/10.1039/C7SM01788J}, DOI={10.1039/c7sm01788j}, abstractNote={Nanocomposites prepared by incorporating polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford versatile hybrid materials but are exquisitely sensitive to even POSS monofunctionalization.}, number={46}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Caydamli, Yavuz and Yildirim, Erol and Shen, Jialong and Fang, Xiaomeng and Pasquinelli, Melissa A. and Spontak, Richard J. and Tonelli, Alan E.}, year={2017}, month={Dec}, pages={8672–8677} }
 @article{ansaloni_dai_ryan_mineart_yu_saud_hägg_spontak_deng_2017, title={Solvent-Templated Block Ionomers for Base- and Acid-Gas Separations: Effect of Humidity on Ammonia and Carbon Dioxide Permeation}, volume={4}, ISSN={2196-7350}, url={http://dx.doi.org/10.1002/ADMI.201700854}, DOI={10.1002/ADMI.201700854}, abstractNote={As energy needs continue to drive the development of biogas and fossil-fuel technologies, methods by which to selectively remove basic (NH3) and acidic (CO2) gases are becoming increasingly important, especially in light of global climate change. Block copolymers are considered as suitable membrane candidates in gas separations due to the ability of such copolymers to microphase-separate and spontaneously form nanoscale morphologies that exhibit spatially modulated chemical specificity. Incorporation of charged moieties along the midblock of a thermoplastic elastomeric multiblock copolymer yields an amphiphilic block ionomer possessing a flexible molecular network stabilized by rigid endblocks. The presence of hydrophilic microdomains introduces an important consideration regulating molecular transport: humidity. In this study, solvent-templating paradigms are employed to control the morphologies of midblock-sulfonated pentablock ionomers, as discerned by electron microscopy and X-ray scattering. The effect of humidity on the permeation of NH3, CO2, and N2 is then investigated through the resulting membranes. As expected, NH3 permeates significantly faster than N2, especially under humid conditions. Although not as pronounced, similar behavior is observed for CO2, thereby establishing that this block ionomer is generally selective to humidified polar gases.}, number={22}, journal={Advanced Materials Interfaces}, publisher={Wiley}, author={Ansaloni, Luca and Dai, Zhongde and Ryan, Justin J. and Mineart, Kenneth P. and Yu, Qiang and Saud, Keara T. and Hägg, May-Britt and Spontak, Richard J. and Deng, Liyuan}, year={2017}, month={Sep}, pages={1700854} }
 @article{al-mohsin_mineart_armstrong_spontak_2017, title={Tuning the performance of aqueous photovoltaic elastomer gels by solvent polarity and nanostructure development}, volume={55}, ISSN={["1099-0488"]}, DOI={10.1002/polb.24242}, abstractNote={In this study, a sulfonated pentablock ionomer is considered for use as an aqueous gel electrolyte in photovoltaic elastomer gels (PVEGs) containing photosensitive dyes. Depending on the casting solvent employed, these materials order into different nanoscale morphologies, some of which inherently consist of a continuous pathway through which ions and other polar species are able to diffuse, while others transform into continuous channels upon exposure to water. Here, we examine the effect of solvent polarity during film casting, vapor annealing, and liquid immersion on block ionomer morphology and PVEG photovoltaic performance. Casting the block ionomers from a mixed nonpolar/polar solvent promotes the formation of dispersed ion-rich spherical microdomains. Alternatively, the use of a single polar solvent produces coexisting nonpolar cylinders and lamellae. Exposure of either morphology to polar solvent vapor causes the block ionomers to restructure into a lamellar morphology, whereas exposure of dispersed ion-rich microdomains to water induces a transformation to an irregular morphology composed of continuous ionic channels, which provide an effective pathway for ion diffusion and, consequently, the highest photovoltaic efficiency. In addition to their photovoltaic efficacy, these aqueous gels possess improved mechanical properties (in terms of tensile strength and elastic modulus) in the presence of photosensitive dyes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 85–95}, number={1}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Al-Mohsin, Heba A. and Mineart, Kenneth P. and Armstrong, Daniel P. and Spontak, Richard J.}, year={2017}, month={Jan}, pages={85–95} }
 @article{mineart_lee_spontak_2016, title={A Solvent-Vapor Approach toward the Control of Block lonomer Morphologies}, volume={49}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.6b00134}, abstractNote={Sulfonated block ionomers possess advantageous properties for a wide range of diverse applications such as desalination membranes, fuel cells, electroactive media, and photovoltaic devices. Unfortunately, their inherently high incompatibilities and glass transition temperatures effectively prevent the use of thermal annealing, routinely employed to refine the morphologies of nonionic block copolymers. An alternative approach is therefore required to promote morphological equilibration in block ionomers. The present study explores the morphological characteristics of midblock-sulfonated pentablock ionomers (SBIs) differing in their degree of sulfonation (DOS) and cast from solution followed by solvent-vapor annealing (SVA). Transmission electron microscopy confirms that films deposited from different solvent systems form nonequilibrium morphologies due to solvent-regulated self-assembly and drying. A series of SVA tests performed with solvents varying in polarity reveals that exposing cast films to tetrahydrofuran (THF) vapor for at least 2 h constitutes the most effective SVA protocol, yielding the anticipated equilibrium morphology. That is, three SBI grades subjected to THF-SVA self-assemble into well-ordered lamellae wherein the increase in DOS is accompanied by an increase in lamellar periodicity, as measured by small-angle X-ray scattering.}, number={8}, journal={MACROMOLECULES}, author={Mineart, Kenneth P. and Lee, Byeongdu and Spontak, Richard J.}, year={2016}, month={Apr}, pages={3126–3137} }
 @article{tallury_pourdeyhimi_pasquinelli_spontak_2016, title={Macromol. Rapid Commun. 22/2016}, volume={37}, ISSN={1022-1336}, url={http://dx.doi.org/10.1002/MARC.201670085}, DOI={10.1002/MARC.201670085}, number={22}, journal={Macromolecular Rapid Communications}, publisher={Wiley}, author={Tallury, Syamal S. and Pourdeyhimi, Behnam and Pasquinelli, Melissa A. and Spontak, Richard J.}, year={2016}, month={Nov}, pages={1785–1785} }
 @article{lunn_gould_whittell_armstrong_mineart_winnik_spontak_pringle_manners_2016, title={Microfibres and macroscopic films from the coordination-driven hierarchical self-assembly of cylindrical micelles}, volume={7}, ISSN={["2041-1723"]}, DOI={10.1038/ncomms12371}, abstractNote={Abstract Anisotropic nanoparticles prepared from block copolymers are of growing importance as building blocks for the creation of synthetic hierarchical materials. However, the assembly of these structural units is generally limited to the use of amphiphilic interactions. Here we report a simple, reversible coordination-driven hierarchical self-assembly strategy for the preparation of micron-scale fibres and macroscopic films based on monodisperse cylindrical block copolymer micelles. Coordination of Pd(0) metal centres to phosphine ligands immobilized within the soluble coronas of block copolymer micelles is found to induce intermicelle crosslinking, affording stable linear fibres comprised of micelle subunits in a staggered arrangement. The mean length of the fibres can be varied by altering the micelle concentration, reaction stoichiometry or aspect ratio of the micelle building blocks. Furthermore, the fibres aggregate on drying to form robust, self-supporting macroscopic micelle-based thin films with useful mechanical properties that are analogous to crosslinked polymer networks, but on a longer length scale.}, journal={NATURE COMMUNICATIONS}, author={Lunn, David J. and Gould, Oliver E. C. and Whittell, George R. and Armstrong, Daniel P. and Mineart, Kenneth P. and Winnik, Mitchell A. and Spontak, Richard J. and Pringle, Paul G. and Manners, Ian}, year={2016}, month={Aug} }
 @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{armstrong_mineart_lee_spontak_2016, title={Olefinic Thermoplastic Elastomer Gels: Combining Polymer Crystallization and Microphase Separation in a Selective Solvent}, volume={5}, ISSN={["2161-1653"]}, DOI={10.1021/acsmacrolett.6b00677}, abstractNote={Since selectively swollen thermoplastic elastomer gels (TPEGs) afford a wide range of beneficial properties that open new doors to developing elastomer-based technologies, we examine the unique structure–property behavior of TPEGs composed of olefinic block copolymers (OBCs) in this study. Unlike their styrenic counterparts typically possessing two chemically different blocks, this class of multiblock copolymers consists of linear polyethylene hard blocks and poly(ethylene-co-α-octene) soft blocks, in which case, microphase separation between the hard and the soft blocks is accompanied by crystallization of the hard blocks. Here, we prepare olefinic TPEGs (OTPEGs) through the incorporation of a primarily aliphatic oil that selectively swells the soft block and investigate the resultant morphological features through the use of polarized light microscopy and small-/wide-angle X-ray scattering. These features are correlated with thermal and mechanical property measurements from calorimetry, rheology, and extensiometry to elucidate the roles of crystallization and self-assembly on gel characteristics and establish useful structure–property relationships.}, number={11}, journal={ACS MACRO LETTERS}, author={Armstrong, Daniel P. and Mineart, Kenneth P. and Lee, Byeongdu and Spontak, Richard J.}, year={2016}, month={Nov}, pages={1273–1277} }
 @article{mineart_tallury_li_lee_spontak_2016, title={Phase-Change Thermoplastic Elastomer Blends for Tunable Shape Memory by Physical Design}, volume={55}, ISSN={["0888-5885"]}, DOI={10.1021/acs.iecr.6b04039}, abstractNote={Intelligent polymeric materials are of increasing interest in contemporary technologies due to their low cost, light weight, facile processability, and inherent ability to change properties, shape, and/or size upon exposure to an external stimulus. In this study, we consider thermally programmable shape-memory polymers (SMPs), which typically rely on chemistry-specific macromolecules composed of two functional species. An elastic, network-forming component permits stretched polymer chains to return to their relaxed state, and a switching component affords at least one thermal transition to regulate fixation of a desired strain state and return to a previous strain state. Here, we produce designer shape-memory materials by combining thermoplastic elastomeric triblock copolymers with a midblock-selective phase-change additive, thereby yielding shape-memory polymer blends (SMPBs). These materials not only exhibit tunable switch points but also controllable recovery kinetics. We further highlight the versatil...}, number={49}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Mineart, Kenneth P. and Tallury, Syamal S. and Li, Tao and Lee, Byeongdu and Spontak, Richard J.}, year={2016}, month={Dec}, pages={12590–12597} }
 @article{tallury_pourdeyhimi_pasquinelli_spontak_2016, title={Physical Microfabrication of Shape-Memory Polymer Systems via Bicomponent Fiber Spinning}, volume={37}, ISSN={["1521-3927"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84990927878&partnerID=MN8TOARS}, DOI={10.1002/marc.201600235}, abstractNote={As emerging technologies continue to require diverse materials capable of exhibiting tunable stimuli-responsiveness, shape-memory materials are of considerable significance because they can change size and/or shape in controllable fashion upon environmental stimulation. Of particular interest, shape-memory polymers (SMPs) have secured a central role in the ongoing development of relatively lightweight and remotely deployable devices that can be further designed with specific surface properties. In the case of thermally-activated SMPs, two functional chemical species must be present to provide (i) an elastic network capable of restoring the SMP to a previous strain state and (ii) switching elements that either lock-in or release a temporary strain at a well-defined thermal transition. While these species are chemically combined into a single macromolecule in most commercially available SMPs, this work establishes that, even though they are physically separated across one or more polymer/polymer interfaces, their shape-memory properties are retained in melt-spun bicomponent fibers. In the present study, we investigate the effects of fiber composition and cross-sectional geometry on both conventional and cold-draw shape memory, and report surprisingly high levels of strain fixity and recovery that generally improve upon strain cycling.}, number={22}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, publisher={Wiley-Blackwell}, author={Tallury, Syamal S. and Pourdeyhimi, Behnam and Pasquinelli, Melissa A. and Spontak, Richard J.}, year={2016}, month={Nov}, pages={1837–1843} }
 @article{mineart_al-mohsin_lee_spontak_2016, title={Water-induced nanochannel networks in self-assembled block ionomers}, volume={108}, ISSN={["1077-3118"]}, DOI={10.1063/1.4943505}, abstractNote={Block ionomers cast from solution exhibit solvent-templated morphologies that can be altered by solvent-vapor annealing. When cast from a mixed solvent, a midblock-sulfonated pentablock ionomer self-assembles into spherical ionic microdomains that are loosely connected. Upon exposure to liquid water, nanoscale channels irreversibly develop between the microdomains due to swelling and form a continuous mesoscale network. We use electron tomography and real-time X-ray scattering to follow this transformation and show that the resultant morphology provides a highly effective diffusive pathway.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Mineart, Kenneth P. and Al-Mohsin, Heba A. and Lee, Byeongdu and Spontak, Richard J.}, year={2016}, month={Mar} }
 @article{hemkaew_dechwayukul_aiyarak_spontak_thongruang_2015, title={Batching method and effects of formulation and mechanical loading on electrical conductivity of natural rubber composites filled with multi-wall carbon nanotube and carbon black}, volume={10}, number={3}, journal={Digest Journal of Nanomaterials and Biostructures}, author={Hemkaew, K. and Dechwayukul, C. and Aiyarak, P. and Spontak, R. J. and Thongruang, W.}, year={2015}, pages={883–893} }
 @article{woloszczuk_mineart_spontak_banaszak_2015, title={Dual modes of self-assembly in superstrongly segregated bicomponent triblock copolymer melts}, volume={91}, ISSN={["1550-2376"]}, DOI={10.1103/physreve.91.010601}, abstractNote={While $ABC$ triblock copolymers are known to form a plethora of dual-mode (i.e., order-on-order) nanostructures, bicomponent $ABA$ triblock copolymers normally self-assemble into single morphologies at thermodynamic incompatibility levels up to the strong-segregation regime. In this study, we employ on-lattice Monte Carlo simulations to examine the phase behavior of molecularly asymmetric ${A}_{1}B{A}_{2}$ copolymers possessing chemically identical endblocks differing significantly in length. In the limit of superstrong segregation, interstitial micelles composed of the minority ${A}_{2}$ endblock are observed to arrange into two-dimensional hexagonal arrays along the midplane of $B$-rich lamellae in compositionally symmetric $(50:50 A:B)$ copolymers. Simulations performed here establish the coupled molecular-asymmetry and incompatibility conditions under which such micelles form, as well as the temperature dependence of their aggregation number. Beyond an optimal length of the ${A}_{2}$ endblock, the propensity for interstitial micelles to develop decreases, and the likelihood for colocation of both endblocks in the ${A}_{1}$-rich lamellae increases. Interestingly, the strong-segregation theory of Semenov developed to explain the formation of free micelles by diblock copolymers accurately predicts the onset of interstitial micelles confined at nanoscale dimensions between parallel lamellae.}, number={1}, journal={PHYSICAL REVIEW E}, author={Woloszczuk, Sebastian and Mineart, Kenneth P. and Spontak, Richard J. and Banaszak, Michal}, year={2015}, month={Jan} }
 @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{al-mohsin_mineart_spontak_2015, title={Highly Flexible Aqueous Photovoltaic Elastomer Gels Derived from Sulfonated Block Ionomers}, volume={5}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201401941}, number={8}, journal={ADVANCED ENERGY MATERIALS}, author={Al-Mohsin, Heba A. and Mineart, Kenneth P. and Spontak, Richard J.}, year={2015}, month={Apr} }
 @article{mineart_jiang_jinnai_takahara_spontak_2015, title={Macromol. Rapid Commun. 5/2015}, volume={36}, ISSN={1022-1336}, url={http://dx.doi.org/10.1002/MARC.201570018}, DOI={10.1002/MARC.201570018}, number={5}, journal={Macromolecular Rapid Communications}, publisher={Wiley}, author={Mineart, Kenneth P. and Jiang, Xi and Jinnai, Hiroshi and Takahara, Atsushi and Spontak, Richard J.}, year={2015}, month={Mar}, pages={421–421} }
 @article{mineart_jiang_jinnai_takahara_spontak_2015, title={Morphological Investigation of Midblock-Sulfonated Block Ionomers Prepared from Solvents Differing in Polarity}, volume={36}, ISSN={["1521-3927"]}, DOI={10.1002/marc.201400627}, abstractNote={Recent developments regarding charged multiblock copolymers that can form physical networks and exhibit robust mechanical properties herald new and exciting opportunities for contemporary technologies requiring amphiphilic attributes. Due to the presence of strong interactions, however, control over the phase behavior of such materials remains challenging, especially since their morphologies can be solvent-templated. In this study, transmission electron microscopy and microtomography are employed to examine the morphological characteristics of midblock-sulfonated pentablock ionomers prepared from solvents differing in polarity. Resultant images confirm that discrete, spherical ion-rich microdomains form in films cast from a relatively nonpolar solvent, whereas an apparently mixed morphology with a continuous ion-rich pathway is generated when the casting solvent is more highly polar. Detailed 3D analysis of the morphological characteristics confirms the coexistence of hexagonally-packed nonpolar cylinders and lamellae, which facilitates the diffusion of ions and/or other polar species through the nanostructured medium.}, number={5}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Mineart, Kenneth P. and Jiang, Xi and Jinnai, Hiroshi and Takahara, Atsushi and Spontak, Richard J.}, year={2015}, month={Mar}, pages={432–438} }
 @article{tallury_mineart_woloszczuk_williams_thompson_pasquinelli_banaszak_spontak_2014, title={Communication: Molecular-level insights into asymmetric triblock copolymers: Network and phase development}, volume={141}, ISSN={["1089-7690"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84907545888&partnerID=MN8TOARS}, DOI={10.1063/1.4896612}, abstractNote={Molecularly asymmetric triblock copolymers progressively grown from a parent diblock copolymer can be used to elucidate the phase and property transformation from diblock to network-forming triblock copolymer. In this study, we use several theoretical formalisms and simulation methods to examine the molecular-level characteristics accompanying this transformation, and show that reported macroscopic-level transitions correspond to the onset of an equilibrium network. Midblock conformational fractions and copolymer morphologies are provided as functions of copolymer composition and temperature.}, number={12}, journal={JOURNAL OF CHEMICAL PHYSICS}, publisher={AIP Publishing}, author={Tallury, Syamal S. and Mineart, Kenneth P. and Woloszczuk, Sebastian and Williams, David N. and Thompson, Russell B. and Pasquinelli, Melissa A. and Banaszak, Michal and Spontak, Richard J.}, year={2014}, month={Sep} }
 @article{tallury_mineart_woloszczuk_williams_thompson_pasquinelli_banaszak_spontak_2014, title={Communication: Molecular-level insights into asymmetric triblock copolymers: Network and phase development (vol 141, 121103, 2014)}, volume={141}, ISSN={["1089-7690"]}, url={https://doi.org/10.1063/1.4898353}, DOI={10.1063/1.4898353}, abstractNote={First Page}, number={16}, journal={JOURNAL OF CHEMICAL PHYSICS}, publisher={AIP Publishing}, author={Tallury, Syamal S. and Mineart, Kenneth P. and Woloszczuk, Sebastian and Williams, David N. and Thompson, Russell B. and Pasquinelli, Melissa A. and Banaszak, Michal and Spontak, Richard J.}, year={2014}, month={Oct} }
 @article{tallury_spontak_pasquinelli_2014, title={Dissipative particle dynamics of triblock copolymer melts: A midblock conformational study at moderate segregation}, volume={141}, ISSN={["1089-7690"]}, url={https://doi.org/10.1063/1.4904388}, DOI={10.1063/1.4904388}, abstractNote={As thermoplastic elastomers, triblock copolymers constitute an immensely important class of shape-memory soft materials due to their unique ability to form molecular networks stabilized by physical, rather than chemical, cross-links. The extent to which such networks develop in triblock and higher-order multiblock copolymers is sensitive to the formation of midblock bridges, which serve to connect neighboring microdomains. In addition to bridges, copolymer molecules can likewise form loops and dangling ends upon microphase separation or they can remain unsegregated. While prior theoretical and simulation studies have elucidated the midblock bridging fraction in triblock copolymer melts, most have only considered strongly segregated systems wherein dangling ends and unsegregated chains become relatively insignificant. In this study, simulations based on dissipative particle dynamics are performed to examine the self-assembly and networkability of moderately segregated triblock copolymers. Utilizing a density-based cluster-recognition algorithm, we demonstrate how the simulations can be analyzed to extract information about microdomain formation and permit explicit quantitation of the midblock bridging, looping, dangling, and unsegregated fractions for linear triblock copolymers varying in chain length, molecular composition, and segregation level. We show that midblock conformations can be sensitive to variations in chain length, molecular composition, and bead repulsion, and that a systematic investigation can be used to identify the onset of strong segregation where the presence of dangling and unsegregated fractions are minimal. In addition, because this clustering approach is robust, it can be used with any particle-based simulation method to quantify network formation of different morphologies for a wide range of triblock and higher-order multiblock copolymer systems.}, number={24}, journal={JOURNAL OF CHEMICAL PHYSICS}, publisher={AIP Publishing}, author={Tallury, Syamal S. and Spontak, Richard J. and Pasquinelli, Melissa A.}, year={2014}, month={Dec} }
 @article{subramani_cakmak_spontak_ghosh_2014, title={Enhanced Electroactive Response of Unidirectional Elastomeric Composites with High-Dielectric-Constant Fibers}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201305821}, abstractNote={A fiber-elastomer composite design with a vastly improved and directional actuation response is proposed for dielectric elastomer actuators. The all-elastomer composites are capable of achieving remarkably high actuation stresses, directional strains, electromechanical coupling efficiencies, and energy densities at relatively low electric fields. Their electromechanical metrics are among the highest reported for this class of electroactive materials.}, number={18}, journal={ADVANCED MATERIALS}, author={Subramani, Krishna Bala and Cakmak, Enes and Spontak, Richard J. and Ghosh, Tushar K.}, year={2014}, month={May}, pages={2949–2953} }
 @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{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{vargantwar_brannock_tauer_spontak_2013, title={Midblock-sulfonated triblock ionomers derived from a long-chain poly[styrene-b-butadiene-b-styrene] triblock copolymer}, volume={1}, ISSN={["2050-7496"]}, DOI={10.1039/c2ta00022a}, abstractNote={Selective sulfonation of a poly[styrene-b-butadiene-b-styrene] (SBS) triblock copolymer has been performed with a sulfur trioxide–dioxane (SO3–dioxane) complex to generate midblock-sulfonated triblock ionomers possessing varying degrees of sulfonation (DOS). Products of the sulfonation reaction have been characterized by proton nuclear magnetic resonance and Fourier-transform infrared spectroscopies to ensure sulfonation only involves the B midblocks. Due to this targeted sulfonation, the lower glass transition temperature (Tg) disappears completely in all the ionomers examined, indicating that the formation of ionic aggregates restricts the mobility of the B midblocks. Such aggregates hinder microphase separation and promote a diffuse interface, as established by progressive broadening of the upper Tg with increasing DOS. Additional evidence of diffuse interfaces and matrix densification is provided by small-angle X-ray scattering, which reveals a concurrent size reduction in microdomain spacing with increasing DOS. A sulfonation-induced order–order morphological transition from cylinders to lamellae is likewise observed. Due to the retention of microphase-separated glassy microdomains that serve as physical crosslinks, these triblock ionomers are capable of absorbing remarkably high solvent levels and forming highly swollen gel networks in polar media, thereby making them suitable for use in hygiene and healthcare applications, as well as in devices requiring ion transport.}, number={10}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Vargantwar, Pruthesh H. and Brannock, Molly C. and Tauer, Klaus and Spontak, Richard J.}, year={2013}, pages={3430–3439} }
 @article{woloszczuk_banaszak_spontak_2013, title={Monte-carlo simulations of the order-disorder transition depression in ABA triblock copolymers with a short terminal block}, volume={51}, ISSN={["1099-0488"]}, DOI={10.1002/polb.23215}, abstractNote={Although most ABA triblock copolymers are molecularly symmetric (i.e., the terminal blocks possess the same mass), molecularly asymmetric A1BA2 triblock copolymers are of greater fundamental interest in that they can be used to explore the transition from diblock to triblock copolymer in systematic fashion. In this study, we use a lattice Monte Carlo method known as the cooperative motion algorithm to simulate molten ABA triblock copolymers possessing a short terminal block to explore the effect of molecular asymmetry on the copolymer order–disorder transition (ODT). Reduced ODT temperatures, discerned by simultaneously analyzing several features of the simulation results, are found to compare favorably with experimental data. Of particular interest here is the initial depression in the ODT temperature for A1BA2 copolymers possessing a relatively short terminal (A2) block. This signature feature is successfully captured by the simulations and is found to be strongly dependent on composition, but weakly dependent on copolymer chain length. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013}, number={5}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Woloszczuk, S. and Banaszak, M. and Spontak, R. J.}, year={2013}, month={Mar}, pages={343–348} }
 @article{piephoff_rasmussen_spontak_2013, title={Nanoscale distribution and segregation of midblock-selective co-penetrants in ABA triblock copolymer lamellae}, volume={3}, ISSN={["2046-2069"]}, DOI={10.1039/c3ra44253e}, abstractNote={In addition to their attractive and tunable macroscopic properties, microphase-ordered block copolymers serve as model systems capable of providing fundamental insight into the thermodynamic factors that govern the arrangement of spatially-confined molecules in soft, nanostructured environments. Of particular interest in this study is the spatial distribution of co-penetrant molecules in the design of dense polymeric materials intended for use as gas-separation membranes or responsive sensors. Here, we employ self-consistent field theory to examine the spatial distributions of two midblock-selective co-penetrants in ordered triblock copolymers exhibiting the lamellar morphology. Our results establish how differences in block copolymer incompatibility and penetrant selectivity, size and concentration affect the spatial distributions of the penetrant species, and reveal the extent to which macroscopically miscible penetrants spatially segregate due to nanoscale confinement.}, number={45}, journal={RSC ADVANCES}, author={Piephoff, D. Evan and Rasmussen, Kim O. and Spontak, Richard J.}, year={2013}, pages={22863–22867} }
 @article{toprakci_kalanadhabhatla_spontak_ghosh_2013, title={Polymer Nanocomposites Containing Carbon Nanofibers as Soft Printable Sensors Exhibiting Strain-Reversible Piezoresistivity}, volume={23}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201300034}, abstractNote={Designed as flexible and extendable conductive print media for pervasive computing as strain sensors, nanocomposites composed of a plasticized thermoplastic or a cross-linked elastomer and containing carbon nanofibers at concentrations just above the percolation threshold are observed to exhibit a uniquely strain-reversible piezoresistive response upon application of quasi-static tensile strain. At small strain levels, the electrical resistance of these nanocomposites reduces with increasing strain, indicative of negative piezoresistivity. Beyond a critical strain, however, the resistance reverses and increases with increasing strain, revealing the existence of a negative-to-positive piezoresistivity transition that is fully strain-reversible and repeatable upon strain cycling. These characteristics imply that the nanocomposite morphologies are highly stable with little evidence of mechanical hysteresis. The mechanism underlying this transition is attributed to reorientation of high-aspect-ratio nanofibers (initially homogeneously dispersed) at low strains, followed by separation at high strains. While deposition of these nanocomposites as robust print coatings on textile fabric alters the percolation threshold, strain-reversible piezoresistivity is retained, confirming that they are suitable as printable strain sensors.}, number={44}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Toprakci, Hatice A. K. and Kalanadhabhatla, Saral K. and Spontak, Richard J. and Ghosh, Tushar K.}, year={2013}, month={Nov}, pages={5536–5542} }
 @article{mineart_lin_desai_krishnan_spontak_dickey_2013, title={Ultrastretchable, cyclable and recyclable 1- and 2-dimensional conductors based on physically cross-linked thermoplastic elastomer gels}, volume={9}, ISSN={["1744-6848"]}, DOI={10.1039/c3sm51136g}, abstractNote={Stretchable conductors maintain electrical conductivity at large strains relative to their rigid counterparts that fail at much lower strains. Here, we demonstrate ultrastretchable conductors that are conductive to at least 600% strain and may be strain-cycled without significant degradation to the mechanical or electrical properties. The conductors consist of a liquid metal alloy injected into microchannels composed of triblock copolymer gels. Rheological measurements identify the temperature window over which these gels may be molded and laminated to form microchannels without collapsing the microscale features. Mechanical measurements identify the gel composition that represents a compromise between minimizing modulus (to allow the polymer to be stretched with ease) and maximizing interfacial adhesion strength at the laminated polymer–polymer interface. The resulting 2D stretchable conductors are notable for their ability to maintain electrical conductivity up to large strains, their mechanical durability, and their ability to be recycled easily with full recovery of the component species.}, number={32}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Mineart, Kenneth P. and Lin, Yiliang and Desai, Sharvil C. and Krishnan, Arjun S. and Spontak, Richard J. and Dickey, Michael D.}, year={2013}, pages={7695–7700} }
 @article{vargantwar_roskov_ghosh_spontak_2012, title={Enhanced Biomimetic Performance of Ionic Polymer-Metal Composite Actuators Prepared with Nanostructured Block Ionomers}, volume={33}, ISSN={["1022-1336"]}, DOI={10.1002/marc.201100535}, abstractNote={Ionic polymer–metal composites (IPMCs) represent an important class of stimuli-responsive polymers that are capable of bending upon application of an electric potential. Conventional IPMCs, prepared with Nafion and related polyelectrolytes, often suffer from processing challenges, relatively low actuation levels and back relaxation during actuation. In this study, we examine and compare the effects of fabrication and solvent on the actuation behavior of a block ionomer with a sulfonated midblock and glassy endblocks that are capable of self-organizing and thus stabilizing a molecular network in the presence of a polar solvent. Unlike Nafion, this material can be readily dissolved and cast from solution to yield films that vary in thickness and exhibit enormous solvent uptake. Cycling the initial chemical deposition of Pt on the surfaces of swollen films (the compositing process) increases the extent to which the electrodes penetrate the films, thereby improving contact along the polymer/electrode interface. The maximum bending actuation measured from IPMCs prepared with different solvents is at least comparable, but is often superior, to that reported for conventional IPMCs, without evidence of back relaxation. An unexpected characteristic observed here is that the actuation direction can be solvent regulated. Our results confirm that this block ionomer constitutes an attractive alternative for use in IPMCs and their associated applications.}, number={1}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Vargantwar, Pruthesh H. and Roskov, Kristen E. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2012}, month={Jan}, pages={61–68} }
 @article{krishnan_spontak_2012, title={Factors affecting time-composition equivalence in ternary block copolymer/cosolvent systems}, volume={8}, ISSN={["1744-6848"]}, DOI={10.1039/c1sm06672b}, abstractNote={Time–temperature rheological equivalence is one of the most important and broadly used concepts developed with regard to the viscoelastic behavior of polymers. In this study, we explore the generality of an analogous relationship, time–composition equivalence, in several series of ternary block copolymer/cosolvent systems at ambient temperature. Of particular interest are triblock copolymers solvated with a miscible mixture of midblock-selective solvents to yield physical gels. Such gels, consisting of a midblock-rich network stabilized by glassy endblock-rich microdomains, exhibit remarkable elasticity. The copolymers employed here are styrenic thermoplastic elastomers, whereas the solvents include an aliphatic/alicyclic mineral oil and several different tackifying resins varying in molecular weight and, hence, viscosity. Despite changes in solvent properties, time–composition superpositioning (tCS) yields master curves wherein the composition shift factors consistently scale with cosolvent zero-shear viscosity. Corresponding scaling exponents vary linearly with copolymer concentration and change slope at a morphological transition. Failure of tCS at low frequencies can be largely avoided by implementing copolymers with high-molecular-weight endblocks.}, number={5}, journal={SOFT MATTER}, author={Krishnan, Arjun S. and Spontak, Richard J.}, year={2012}, pages={1334–1343} }
 @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{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{vargantwar_roskov_ghosh_spontak_2012, title={Macromol. Rapid Commun. 1/2012}, volume={33}, ISSN={1022-1336}, url={http://dx.doi.org/10.1002/marc.201290003}, DOI={10.1002/marc.201290003}, number={1}, journal={Macromolecular Rapid Communications}, publisher={Wiley}, author={Vargantwar, Pruthesh H. and Roskov, Kristen E. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2012}, month={Jan}, pages={100–100} }
 @article{roskov_atkinson_bronstein_spontak_2012, title={Magnetic field-induced alignment of nanoparticles in electrospun microfibers}, volume={2}, ISSN={["2046-2069"]}, DOI={10.1039/c2ra20489d}, abstractNote={We report on the facile and switchable alignment of superparamagnetic iron oxide nanoparticles measuring ∼18 nm in diameter in electrospun microfibers. Application of a magnetic field perpendicular to the electric field employed during electrospinning yields polymeric microfibers with nanoparticles aligned in one-dimensional arrays, thereby providing control over when and where the nanoparticles align. According to electron microscopy, the length over which alignment is desired can be judiciously selected, thereby making these nanomaterials excellent candidates for nanotechnologies requiring nanoscale alignment on-demand. Concurrent alignment of the electrospun fibers using established procedures provides a viable route to organic/inorganic materials possessing anisotropic properties that reflect multiscale alignment.}, number={11}, journal={RSC ADVANCES}, author={Roskov, Kristen E. and Atkinson, Jessie E. and Bronstein, Lyudmila M. and Spontak, Richard J.}, year={2012}, pages={4603–4607} }
 @article{vargantwar_brannock_smith_spontak_2012, title={Midblock sulfonation of a model long-chain poly(p-tert-butylstyrene-b-styrene-b-p-tert-butylstyrene) triblock copolymer}, volume={22}, ISSN={0959-9428 1364-5501}, url={http://dx.doi.org/10.1039/c2jm35504c}, DOI={10.1039/c2jm35504c}, abstractNote={Homopolymers containing ionic moieties such as sulfonic acid groups are suitable as fuel-cell, water-purification and ion-exchange membranes or, alternatively, as electroactive or otherwise stimuli-responsive soft materials. Block ionomers constitute a class of ionomers in which (i) long sequences of repeat units are sufficiently incompatible to microphase-separate and (ii) at least one sequence possesses ionic groups along its backbone. In this study, the midblock of a model poly(p-tert-butylstyrene-b-styrene-b-p-tert-butylstyrene) (TST) triblock copolymer has been selectively sulfonated to different degrees by reaction with acetyl sulfate. Self-assembly of the unaffected endblocks prevents the resultant block ionomers from dissolving in water and imparts water-swollen ionomer films with sufficient mechanical integrity to remain intact. The degree of sulfonation is controlled by varying the concentration of acetyl sulfate, as confirmed by spectroscopic analyses. An increase in ionic content promotes a reduction in thermal stability due to sulfonic acid cleaving, but a significant increase in water sorption that increases with increasing temperature. Although the parent TST copolymer is disordered according to small-angle X-ray scattering, moderate levels of midblock sulfonation induce microphase ordering and simultaneously increase the intermicrodomain distance due to swelling considerations.}, number={48}, journal={Journal of Materials Chemistry}, publisher={Royal Society of Chemistry (RSC)}, author={Vargantwar, Pruthesh H. and Brannock, Molly C. and Smith, Steven D. and Spontak, Richard J.}, year={2012}, pages={25262} }
 @article{arvidson_roskov_pate_spontak_khan_gorga_2012, title={Modification of Melt-Spun Isotactic Polypropylene and Poly(lactic acid) Bicomponent Filaments with a Premade Block Copolymer}, volume={45}, ISSN={["1520-5835"]}, DOI={10.1021/ma202246h}, abstractNote={While numerous studies have investigated the effect of adding a block copolymer as a macromolecular surfactant to immiscible polymer blends, no such efforts have sought to alter the properties of melt-spun bicomponent core–sheath filaments with a nonreactive compatibilizing agent. In this study, we examine the effect of adding poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymer to core–sheath filaments consisting of isotactic polypropylene (iPP) and poly(lactic acid) (PLA). Incorporation of the copolymer into blends of iPP/PLA is observed to reduce the size scale of phase separation. Interfacial slip between molten iPP and PLA layers is evaluated by rheology under steady-shear conditions. Addition of SEBS to the PLA sheath during filament formation reduces the tendency of PLA sheaths to crack prior to iPP core failure during tensile testing. In reversed filament configurations, the copolymer does not hinder the development of molecular orientation, related to fiber strength, during fiber spinning. Electron microscopy reveals that the copolymer molecules form unique, highly nonequilibrium morphologies under the spinning conditions employed here.}, number={2}, journal={MACROMOLECULES}, author={Arvidson, Sara A. and Roskov, Kristen E. and Pate, Jaimin J. and Spontak, Richard J. and Khan, Saad A. and Gorga, Russell E.}, year={2012}, month={Jan}, pages={913–925} }
 @article{vargantwar_oezcam_ghosh_spontak_2012, title={Prestrain-Free Dielectric Elastomers Based on Acrylic Thermoplastic Elastomer Gels: A Morphological and (Electro)Mechanical Property Study}, volume={22}, ISSN={["1616-301X"]}, DOI={10.1002/adfm.201101985}, abstractNote={Recent efforts have established that thermoplastic elastomer gels (TPEGs) composed of styrenic triblock copolymers swollen with a midblock-selective solvent exhibit remarkable electromechanical properties as high-performance dielectric elastomers. This class of electroactive polymers typically requires high electric fields for actuation, and a shortcoming that continues to thwart the widespread commercialization of such materials in general is the need to apply mechanical prestrain prior to electroactuation to decrease film thickness and, thus, the electric potential required to promote actuation. To alleviate this requirement, TPEGs consisting of acrylic triblock copolymers differing in molecular weight and composition, and swollen with a high dielectric, midblock-selective solvent are investigated. Synchrotron small-angle x-ray scattering is used to probe the nanoscale morphologies of the resultant materials, and analysis of quasi-static and cyclic tensile properties provides additional insight into both blend morphologies and electroactuation efficacy. Actuation strains measured in the absence of mechanical prestrain exceed 100% on an area basis, and electric fields capable of inducing actuation are as low as ∼20 kV/mm. Failure occurs by either electromechanical instability or dielectric breakdown, depending on the copolymer and TPEG composition employed. The electromechanical properties of these acrylic-based TPEGs match or exceed those of skeletal muscle, in which case they constitute an attractive and unexplored alternative to existing dielectric elastomers.}, number={10}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Vargantwar, Pruthesh H. and Oezcam, A. Evren and Ghosh, Tushar K. and Spontak, Richard J.}, year={2012}, month={May}, pages={2100–2113} }
 @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} }
 @article{krishnan_smith_spontak_2012, title={Ternary Phase Behavior of a Triblock Copolymer in the Presence of an Endblock-Selective Homopolymer and a Midblock-Selective Oil}, volume={45}, ISSN={["1520-5835"]}, DOI={10.1021/ma300417u}, abstractNote={Bicomponent block copolymers are known to exhibit rich phase behavior in systems containing one or two block-selective homopolymers or solvents. In this study, we combine these efforts by investigating ternary blends composed of an ABA triblock copolymer, an A-selective homopolymer and a B-selective oil. A styrenic thermoplastic elastomer is selected here because of its ability to form a physical network upon microphase separation and thus impart significant elasticity and toughness to such blends. Synchrotron small-angle X-ray scattering is employed to classify the nanostructures of blends varying in composition, homopolymer molecular weight, and oil type, and the results are used to construct ternary morphology diagrams that reveal the phases present at the glass transition temperature of the styrenic endblocks. Of all the classical and complex morphologies commonly observed in binary copolymer blends and solutions, only the bicontinuous gyroid consisting of styrenic channels in a mixed midblock/oil matrix is consistently absent. Variations in nanostructural dimensions with blend composition are provided for selected morphologies.}, number={15}, journal={MACROMOLECULES}, author={Krishnan, Arjun S. and Smith, Steven D. and Spontak, Richard J.}, year={2012}, month={Aug}, pages={6056–6067} }
 @article{krishnan_vargantwar_spontak_2012, title={Thermorheological behavior of coexisting physical networks: combining SAFIN and SAMIN organogels}, volume={8}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/c2sm26698a}, DOI={10.1039/c2sm26698a}, abstractNote={Organogels, like their hydrogel analogs in aqueous media, consist of chemically or physically cross-linked networks that endow simple (or even viscoelastic) organic liquids with solid-like characteristics. Of particular interest here are physical networks composed of either low-molar-mass organic gelators, which tend to form self-assembled fibrillar networks (SAFINs) by site-specific interactions such as hydrogen bonding and/or π–π stacking, or microphase-separated triblock copolymers, which form self-assembled micellar networks (SAMINs) due primarily to bridged midblocks that connect neighboring micelles. In this study, we combine these two physical networks by mixing the gelator 1,3:2,4-dibenzylidene-D-sorbitol with a series of midblock-swollen triblock copolymers differing in molecular weight to produce coexisting SAFIN/SAMIN networks in two midblock-selective solvents differing in polarity. The thermorheological properties of the resultant mixed network systems are investigated for three cases: (i) the order–disorder transition temperature (TODT) of the SAMIN is much lower than the dissolution temperature (Td) of the SAFIN, (ii) TODT < Td and (iii) TODT ≈ Td. Employing dynamic rheology, we show how these transitions are affected by the order in which self-organization occurs.}, number={48}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Krishnan, Arjun S. and Vargantwar, Pruthesh H. and Spontak, Richard J.}, year={2012}, pages={12025} }
 @article{vargantwar_brelander_krishnan_ghosh_spontak_2011, title={(Electro)mechanical behavior of selectively solvated diblock/triblock copolymer blends}, volume={99}, ISSN={["1077-3118"]}, DOI={10.1063/1.3666783}, abstractNote={Thermoplastic elastomeric triblock copolymers swollen with a midblock-selective solvent form a highly elastic physical network that can exhibit remarkable electromechanical properties (high actuation strains and electromechanical efficiency with low hysteresis upon cycling) as dielectric elastomers. One unexplored means of controllably altering the midblock network and the corresponding (electro)mechanical properties at constant copolymer concentration is to substitute non-network-forming diblock for triblock copolymer molecules. In this study, we demonstrate that the incorporation of composition-matched diblock molecules into selectively solvated triblock systems results in softer materials that are less physically crosslinked and thus capable of undergoing electroactuation at reduced electric fields.}, number={24}, journal={APPLIED PHYSICS LETTERS}, author={Vargantwar, Pruthesh H. and Brelander, Sarah M. and Krishnan, Arjun S. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2011}, month={Dec} }
 @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{krishnan_spontak_2011, title={Deviation from time-composition equivalence in polymer solutions with selective cosolvents}, volume={1}, ISSN={["2158-3226"]}, DOI={10.1063/1.3666980}, abstractNote={Time-composition superpositioning (tCS) permits determination of the mechanical properties of polymeric materials over a widely extended time (or frequency) domain by systematically varying composition under isothermal conditions. We have recently reported (Soft Matter, 6, 4331, 2010) the existence of such equivalence in technologically relevant triblock copolymers swollen with miscible, midblock-selective cosolvents differing in chemical constitution and viscosity. In this study, chemically homologous homopolymer and copolymer systems exhibiting rheological properties that deviate from tCS are investigated. With regard to the particular case of selectively solvated triblock copolymers, the source of deviation is explained in the context of endblock hopping.}, number={4}, journal={AIP ADVANCES}, author={Krishnan, Arjun S. and Spontak, Richard J.}, year={2011}, month={Dec} }
 @article{krishnan_vargantwar_ghosh_spontak_2011, title={Electroactuation of Solvated Triblock Copolymer Dielectric Elastomers: Decoupling the Roles of Mechanical Prestrain and Specimen Thickness}, volume={49}, ISSN={["1099-0488"]}, DOI={10.1002/polb.22331}, abstractNote={Dielectric elastomers (DEs) constitute a class of electroactive polymers that are becoming increasingly important as lightweight and mechanically robust replacements for conventional transducers and actuators. Because of their inherent cycling resilience, they also show tremendous promise as energy-harvesting media, as well as smart sensors and microfluidic devices. Recent studies have demonstrated that DEs composed of midblock-solvated triblock copolymers exhibit attractive electromechanical attributes such as giant electroactuation strains at relatively low electric fields at high conversion efficiency. Moreover, the properties of these readily processable systems are highly composition-tunable, thereby making them ideal candidates for a detailed study of the coupling between initial specimen thickness and mechanical prestrain, which is frequently used to reduce specimen thickness before actuation to lower the voltage required to achieve electroactuation. Conventional wisdom based on the notion of an ideal DE indicates that electroactuation should only depend on pre-actuation specimen thickness, but we report results that unequivocally indicate a more detailed material/process description is required. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1569–1582, 2011}, number={22}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Krishnan, Arjun S. and Vargantwar, Pruthesh H. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2011}, month={Nov}, pages={1569–1582} }
 @article{vargantwar_shankar_krishnan_ghosh_spontak_2011, title={Exceptional versatility of solvated block copolymer/ionomer networks as electroactive polymers}, volume={7}, ISSN={["1744-6848"]}, DOI={10.1039/c0sm01210f}, abstractNote={Responsive materials possess properties that change abruptly when exposed to an external stimulus, and electroactive polymers constitute examples of robust, lightweight materials that change shape upon electrical actuation. We demonstrate that solvated block copolymer networks afford tremendous versatility in designing electronic and ionic electroactive polymers. As dielectric elastomers, styrenic block copolymer systems attain extraordinary actuation strains approaching 300%, along with high electromechanical coupling efficiencies. Changing the solvent improves the blocking stress and yields remarkably high energy densities, while providing a unique opportunity for mechanical impedance matching and control of shape recovery kinetics, as well as mode of deformation. Dielectric elastomers composed of acrylic copolymers actuate beyond 100% in-plane strain without any prestrain, whereas block ionomer networks swollen with ionic solutions yield ionic polymer–metal composites, which actuate by bending. Selective solvation of block copolymer networks represents an effective and largely unexplored means by which to tune the function and properties of electroactive polymers through systematic manipulation of copolymer and solvent attributes.}, number={5}, journal={SOFT MATTER}, author={Vargantwar, Pruthesh H. and Shankar, Ravi and Krishnan, Arjun S. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2011}, pages={1651–1655} }
 @article{roskov_kozek_wu_chhetri_oldenburg_spontak_tracy_2011, title={Long-Range Alignment of Gold Nanorods in Electrospun Polymer Nano/Microfibers}, volume={27}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/la2021066}, DOI={10.1021/la2021066}, abstractNote={In this study, a scalable fabrication technique for controlling and maintaining the nanoscale orientation of gold nanorods (GNRs) with long-range macroscale order has been achieved through electrospinning. The volume fraction of GNRs with an average aspect ratio of 3.1 is varied from 0.006 to 0.045 in aqueous poly(ethylene oxide) solutions to generate electrospun fibers possessing different GNR concentrations and measuring 40-3000 nm in diameter. The GNRs within these fibers exhibit excellent alignment with their longitudinal axis parallel to the fiber axis n. According to microscopy analysis, the average deviant angle between the GNR axis and n increases modestly from 3.8 to 13.3° as the fiber diameter increases. Complementary electron diffraction measurements confirm preferred orientation of the {100} GNR planes. Optical absorbance spectroscopy measurements reveal that the longitudinal surface plasmon resonance bands of the aligned GNRs depend on the polarization angle and that maximum extinction occurs when the polarization is parallel to n.}, number={23}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Roskov, Kristen E. and Kozek, Krystian A. and Wu, Wei-Chen and Chhetri, Raghav K. and Oldenburg, Amy L. and Spontak, Richard J. and Tracy, Joseph B.}, year={2011}, month={Dec}, pages={13965–13969} }
 @article{krishnan_zanten_seifert_lee_spontak_2011, title={Selectively solvated triblock copolymer networks under biaxial strain}, volume={99}, ISSN={["0003-6951"]}, DOI={10.1063/1.3635780}, abstractNote={Triblock copolymers swollen with a midblock-selective solvent provide a test platform by which to interrogate the properties of highly elastic physical gel networks. Here, such networks are biaxially strained and studied by synchrotron small-angle x-ray scattering. Analysis of the form factor reveals that initially spherical micellar cores deform to ellipsoids when strained. The Percus-Yevick hard-sphere model describes the structure factor of micelles exhibiting liquid-like order prior to deformation but requires an attractive potential to match the structure factor under strain. The magnitude of this potential increases with increasing strain, indicating a change in coronal overlap as the network is stretched.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Krishnan, Arjun S. and Zanten, John H. and Seifert, Soenke and Lee, Byeongdu and Spontak, Richard J.}, year={2011}, month={Sep} }
 @article{gozen_gaines_hamersky_maniadis_rasmussen_smith_spontak_2010, title={Controlling the phase behavior of block copolymers via sequential block growth}, volume={51}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2010.09.006}, abstractNote={Block copolymers remain one of the most extensively investigated classes of polymers due to their abilities to self-organize into various nanostructures and modify polymer/polymer interfaces. Despite fundamental and technological interest in these materials, only a handful of experimental phase diagrams exist due to the laborious task of preparing such diagrams. In this work, two copolymer series are each synthesized from a single macromolecule via sequential living anionic polymerization to yield molecularly asymmetric diblock and triblock copolymers systematically varying in composition. The phase behavior and morphology of these copolymers are experimentally interrogated and quantitatively compared with predictions from mean-field theories, which probe copolymer phase behavior beyond current experimental conditions.}, number={23}, journal={POLYMER}, author={Gozen, Arif O. and Gaines, Michelle K. and Hamersky, Mark W. and Maniadis, Panagiotis and Rasmussen, Kim O. and Smith, Steven D. and Spontak, Richard J.}, year={2010}, month={Oct}, pages={5304–5308} }
 @article{krishnan_seifert_lee_khan_spontak_2010, title={Cosolvent-regulated time-composition rheological equivalence in block copolymer solutions}, volume={6}, ISSN={["1744-6848"]}, DOI={10.1039/c0sm00573h}, abstractNote={The morphological and mechanical attributes of triblock copolymer solutions composed of miscible, midblock-selective solvents are investigated by small-angle scattering and dynamic rheology. Variation in cosolvent composition at constant copolymer concentration has little effect on copolymer morphology, but promotes large differences in matrix relaxation, as evinced by changes in the shape of isothermal frequency spectra. Shifting these spectra in the frequency domain reveals the existence of time–composition equivalence, wherein shift factors scale with the viscosity of the cosolvent mixture.}, number={18}, journal={SOFT MATTER}, author={Krishnan, Arjun S. and Seifert, Soenke and Lee, Byeongdu and Khan, Saad A. and Spontak, Richard J.}, year={2010}, pages={4331–4334} }
 @misc{desimone_siripurapu_khan_spontak_royer_2010, title={Nano-and micro-cellular foamed thin-walled material, and processes and apparatuses for making the same}, volume={7,658,989}, number={2010 Feb. 9}, author={DeSimone, J. M. and Siripurapu, S. and Khan, S. A. and Spontak, R. J. and Royer, J.}, year={2010} }
 @article{gaines_smith_samseth_khan_spontak_2010, title={Nanoparticle Network Formation in Nanostructured and Disordered Block Copolymer Matrices}, volume={5}, ISSN={["1556-276X"]}, DOI={10.1007/s11671-010-9775-y}, abstractNote={Incorporation of nanoparticles composed of surface-functionalized fumed silica (FS) or native colloidal silica (CS) into a nanostructured block copolymer yields hybrid nanocomposites whose mechanical properties can be tuned by nanoparticle concentration and surface chemistry. In this work, dynamic rheology is used to probe the frequency and thermal responses of nanocomposites composed of a symmetric poly(styrene-b-methyl methacrylate) (SM) diblock copolymer and varying in nanoparticle concentration and surface functionality. At sufficiently high loading levels, FS nanoparticle aggregates establish a load-bearing colloidal network within the copolymer matrix. Transmission electron microscopy images reveal the morphological characteristics of the nanocomposites under these conditions.}, number={10}, journal={NANOSCALE RESEARCH LETTERS}, author={Gaines, Michelle K. and Smith, Steven D. and Samseth, Jon and Khan, Saad A. and Spontak, Richard J.}, year={2010}, month={Oct}, pages={1712–1718} }
 @misc{jinnai_spontak_nishi_2010, title={Transmission Electron Microtomography and Polymer Nanostructures}, volume={43}, ISSN={["1520-5835"]}, DOI={10.1021/ma902035p}, abstractNote={This Perspective summarizes the recent advances and perspective in three-dimensional (3D) imaging techniques and their applications to polymer nanostructures, e.g., microphase-separated structures of block copolymers. We place particular emphasis on the method of transmission electron microtomography (TEMT). As a result of some recent developments in TEMT, it is now possible to obtain truly quantitative 3D images of polymer nanostructures with subnanometer resolution. The introduction of scanning optics in TEMT has made it possible to obtain large volumes of 3D data from a micrometer thick polymer specimens using conventional electron microscopes at relatively low acceleration voltage, 200 kV. Thus, TEMT covers structures over a wide range of thicknesses from a few nanometers to several hundred nanometers, which corresponds to quite an important spatial range for hierarchical polymer nanostructures. TEMT provides clear 3D images and a wide range of new structural information, which cannot be obtained using other methods, e.g., conventional microscopy or scattering methods, can be directly evaluated from the 3D volume data. In addition, when combined with other characterization methods, e.g., scattering and computer simulations, TEMT can yield even better results. The single chain conformation of block copolymers inside microdomains may be virtually visualized by TEMT. TEMT is a versatile technique that is not only restricted to polymer applications but can also be used as a powerful characterization tool in energy applications, e.g., fuel cells, etc.}, number={4}, journal={MACROMOLECULES}, author={Jinnai, Hiroshi and Spontak, Richard J. and Nishi, Toshio}, year={2010}, month={Feb}, pages={1675–1688} }
 @article{peng_sun_spagnola_saquing_khan_spontak_parsons_2009, title={Bi-directional Kirkendall Effect in Coaxial Microtuble Nanolaminate Assemblies Fabricated by Atomic Layer Deposition}, volume={3}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000264535200010&KeyUID=WOS:000264535200010}, DOI={10.1021/nn8006543}, abstractNote={The solid-state reaction within a coaxial Al2O3/ZnO/Al2O3 multilayered microtubular structure can be used to prepare discrete microtube-in-microtube ZnAl2O4 spinel assemblies through a Kirkendall void production mechanism at 700 °C. In contrast with previous studies of the nanoscale Kirkendall effect, the reaction observed here proceeds through a bi-directional vacancy diffusion mechanism wherein ZnO species diffuse into inner- and outer-Al2O3 concentric layers, thereby resulting in vacancy supersaturation and void production between two isolated spinel microtubes. Low-temperature atomic layer deposition (ALD) of Al2O3 and ZnO enables the fabrication of complex coaxial multilayered microtubes with precise control of the starting film thicknesses and relative composition. When a molar excess of ZnO is present between two Al2O3 layers, electron microscopy images reveal incomplete ZnO consumption after annealing at 700 °C. At higher initial Al2O3 concentrations, however, complete reaction with ZnO is observed, and the size of the Kirkendall gap between isolated spinel microtubes appears to be directly influenced by the thickness of the intermediate ZnO layer.}, number={3}, journal={ACS NANO}, author={Peng, Qing and Sun, Xiao-Yu and Spagnola, Joseph C. and Saquing, Carl and Khan, Saad A. and Spontak, Richard J. and Parsons, Gregory N.}, year={2009}, month={Mar}, pages={546–554} }
 @article{shankar_klossner_weaver_koga_zanten_krause_colina_tanaka_spontak_2009, title={Competitive hydrogen-bonding in polymer solutions with mixed solvents}, volume={5}, ISSN={["1744-683X"]}, DOI={10.1039/b808479c}, abstractNote={Poly(ethylene oxide) (PEO) coil size is investigated in a binary mixture of solvent molecules capable of cooperatively hydrogen-bonding with each other, as well as with the PEO chains. Viscometry reveals a minimum in zero shear rate solution viscosity at a molar ratio of ∼2:1 water:methanol. This viscosity coincides with a minimum in PEO gyration radius and occurs near the conditions where water/methanol mixtures deviate most markedly from ideal solution behavior. A minimum in polymer mean square end-to-end distance is predicted for polymer solutions composed of two hydrogen-bonding solvents.}, number={2}, journal={SOFT MATTER}, author={Shankar, Ravi and Klossner, Rebecca R. and Weaver, Juan T. and Koga, Tsuyoshi and Zanten, John H. and Krause, Wendy E. and Colina, Coray M. and Tanaka, Fumihiko and Spontak, Richard J.}, year={2009}, pages={304–307} }
 @article{shankar_ghosh_spontak_2009, title={Mechanical and actuation behavior of electroactive nanostructured polymers}, volume={151}, ISSN={["0924-4247"]}, DOI={10.1016/j.sna.2009.01.002}, abstractNote={Electroactive polymers (EAPs) can exhibit relatively large actuation strain responses upon electrical stimulation. For this reason, in conjunction with their light weight, robust properties, low cost and facile processability, EAPs are of considerable interest in the development of next-generation organic actuators. Within this class of materials, dielectric electroactive polymers (D-EAPs) have repeatedly exhibited the most promising and versatile properties. A new family of D-EAPs derived from swollen poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymers has been recently found to undergo ultrahigh displacement at relatively low electric fields compared to previously reported D-EAPs. The present work examines the mechanical and actuation response of these electroactive nanostructured polymer (ENP) systems under quasi-static, and electromechanical loading conditions. Careful measurement of the quasi-static properties under tensile and compressive loading yield similar results that are significantly influenced by the introduction of in-plane strain, as well as by copolymer concentration or molecular weight. Blocking stress measurements reveal that the actuation effectiveness achieved by some of the ENPs is comparable to that of the VHB 4910 acrylic D-EAP, thus providing a novel and efficient avenue to designer D-EAPs for advanced engineering, biomimetic and biomedical applications.}, number={1}, journal={SENSORS AND ACTUATORS A-PHYSICAL}, author={Shankar, Ravi and Ghosh, Tushar K. and Spontak, Richard J.}, year={2009}, month={Apr}, pages={46–52} }
 @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} }
 @misc{jinnai_spontal_2009, title={Transmission electron microtomography in polymer research}, volume={50}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2008.12.023}, abstractNote={This feature article summarizes recent advances in an emerging three-dimensional (3D) imaging technique, transmission electron microtomography (TEMT), and its applications to polymer-related materials, such as nanocomposites and block copolymer morphologies. With the recent developments made in TEMT, it is now possible to obtain truly quantitative 3D data with sub-nanometer resolution. A great deal of new structural information, which has never been obtained by conventional microscopy or various scattering methods, can be directly evaluated from the 3D volume data. It has also been demonstrated that, with the combination of TEMT and scattering methods, it becomes possible to study structures that have not yet been characterized. The structural information obtained from such 3D imaging provides a good opportunity not only to gain essential insight into the physics of self-assembling processes and the statistical mechanics of long chain molecules, but also to establish the “structure–property” relationship in polymeric materials.}, number={5}, journal={POLYMER}, author={Jinnai, Hiroshi and Spontal, Richard J.}, year={2009}, month={Feb}, pages={1067–1087} }
 @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{aberg_ozcam_majikes_seyam_spontak_2008, title={Extended chemical crosslinking of a thermoplastic polyimide: Macroscopic and microscopic property development}, volume={29}, ISSN={["1022-1336"]}, DOI={10.1002/marc.200800230}, abstractNote={Polyimides are well established as gas separation membranes due to their intrinsically low free volume and correspondingly high H2 selectivity relative to other gases such as CO2. Prior studies have established that H2/CO2 selectivity can be improved by crosslinking polyimides with diamines differing in spacer length. In this work, we follow the evolution of macroscopic and microscopic properties of a commercial polyimide over long crosslinking times (tx) with 1,3-diaminopropane. According to spectroscopic analysis, the crosslinking reaction saturates after ≈24 h, whereas tensile, nanoindentation and stress relaxation tests reveal that the material stiffens, and possesses a long relaxation time that increases with increasing tx. Although differential scanning calorimetry shows that the glass transition temperature decreases systematically with increasing tx, permeation studies indicate that the permeabilities of H2 and CO2 decrease, while the H2/CO2 selectivity increases markedly, with increasing tx. At long tx, the polyimide becomes impermeable to CO2, suggesting that it could be used as a barrier material.}, number={17}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Aberg, Christopher M. and Ozcam, Ali E. and Majikes, Jacob M. and Seyam, Mohamed A. and Spontak, Richard J.}, year={2008}, month={Sep}, pages={1461–1466} }
 @article{sun_nobles_boerner_spontak_2008, title={Field-driven surface segregation of biofunctional species on electrospun PMMA/PEO microfibers}, volume={29}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200800163}, abstractNote={The need to biofunctionalize polymer surfaces for targeted bio-related applications continues to grow, and efforts designed to meet this need rely heavily on surface grafting or polymerization. In this study, we provide a viable alternative by demonstrating that the peptide segment of a polymer-peptide conjugate can be selectively driven to the surface of polymer nano/microfibers during electrospinning due to contrast in polarizability. Judicious choice of the polymer sequence in the conjugate permits use of the conjugate with compatible fiber-forming polymers. Here, we use a water soluble poly(ethylene oxide)-containing conjugate in combination with a hydrophobic thermoplastic, poly(methyl methacrylate). Surface enrichment is measured by X-ray photoelectron spectroscopy, and fiber morphology is investigated by electron microscopy. Microfibers generated from the blends examined here are largely resistant to long term water immersion and are thus suited as support scaffolds or filtration membranes.}, number={17}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Sun, Xiao-Yu and Nobles, Larrisha R. and Boerner, Hans G. and Spontak, Richard J.}, year={2008}, month={Sep}, pages={1455–1460} }
 @article{aberg_seyam_lassell_bronstein_spontak_2008, title={In situ Growth of Pd Nanoparticles in Crosslinked Polymer Matrices}, volume={29}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200800505}, abstractNote={Polymer nanocomposites continue to receive considerable attention as multifunctional hybrid materials, with most nanocomposites fabricated by physical dispersion of surface-functionalized nanoscale objects. In this study, we explore the viability of growing Pd-containing nanoparticles from Na2PdCl4 in two different polymers: hypercrosslinked polystyrene (HPS) and an aromatic polyimide (PIm). In HPS, single Pd-containing nanoparticles possessing a relatively narrow size distribution (ca. 1–4 nm) form upon reduction of the divalent PdCl ions. Single nanoparticles with a broad size distribution ranging from ≈2 to 16 nm develop in PIm, which simultaneously undergoes chemical crosslinking during ion reduction. Such hybrid materials hold promise in molecular catalysis and gas separation.}, number={24}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Aberg, Christopher M. and Seyam, Mohamed A. and Lassell, Scott A. and Bronstein, Lyudmila M. and Spontak, Richard J.}, year={2008}, month={Dec}, pages={1926–1931} }
 @article{gaines_smith_samseth_bockstaller_thompson_rasmussen_spontak_2008, title={Nanoparticle-regulated phase behavior of ordered block copolymers}, volume={4}, ISSN={["1744-6848"]}, DOI={10.1039/b805540h}, abstractNote={Although block copolymer motifs have received considerable attention as supramolecular templates for inorganic nanoparticles, experimental observations of a nanostructured diblock copolymer containing inorganic nanoparticles—supported by theoretical trends predicted from a hybrid self-consistent field/density functional theory—confirm that nanoparticle size and selectivity can likewise stabilize the copolymer nanostructure by increasing its order–disorder transition temperature.}, number={8}, journal={SOFT MATTER}, author={Gaines, Michelle K. and Smith, Steven D. and Samseth, Jon and Bockstaller, Michael R. and Thompson, Russell B. and Rasmussen, Kim O. and Spontak, Richard J.}, year={2008}, pages={1609–1612} }
 @misc{walker_frankowski_spontak_2008, title={Thermodynamics and kinetic processes of polymer blends and block copolymers in the presence of pressurized carbon dioxide}, volume={20}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200700076}, abstractNote={Environmentally-responsible materials processing is becoming an important global consideration in a wide variety of technologies, especially those wherein volatile and/or residual organic solvents cannot be tolerated. In this context, polymer processing has benefited tremendously from advances achieved using high-pressure CO2 as a viscosity modifier, plasticizing agent, foaming agent, and reaction medium. Pressurized CO2 is environmentally benign, inexpensive, sustainable, and versatile owing to its gas-like viscosity and liquid-like solubility, which can be tuned through judicious choice of temperature and pressure. The addition of high-pressure CO2 to homopolymer blends and block copolymers can have a profound impact on polymer thermodynamics and kinetic processes since the number of interacting species increases. As a result, the compressibility as well as plasticization and intermolecular screening effects become non-negligible. In this work, we review how these factors influence such polymeric systems, and discuss commercial polymer processes and applications that benefit from the use of high-pressure CO2.}, number={5}, journal={ADVANCED MATERIALS}, author={Walker, Teri A. and Frankowski, David J. and Spontak, Richard J.}, year={2008}, month={Mar}, pages={879–898} }
 @article{shankar_krishnan_ghosh_spontak_2008, title={Triblock copolymer organogels as high-performance dielectric elastomers}, volume={41}, ISSN={["1520-5835"]}, DOI={10.1021/ma071903g}, abstractNote={Block copolymers and nanostructured materials derived therefrom are becoming increasingly ubiquitous in a wide variety of (nano)technologies. Recently, we have demonstrated that triblock copolymer organogels composed of physically cross-linked copolymer networks swollen with a midblock-selective solvent exhibit excellent electromechanical behavior as dielectric elastomers. In-plane actuation of such organogels, collectively referred to as electroactive nanostructured polymers (ENPs) to reflect the existence of a self-organized copolymer morphology, is attributed to the development of an electric-field-induced surface-normal Maxwell stress. In this study, we examine the composition and molecular weight dependence of the electromechanical properties afforded by organogels prepared from poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymers selectively swollen with EB-compatible aliphatic oligomers. These materials undergo ultrahigh actuation displacement at significantly reduced electric fields relative to previously reported dielectric elastomers and possess electromechanical coupling efficiencies, which relate the conversion from electrical input to mechanical output, greater than 90%. The design of ENPs with broadly tunable electromechanical properties represents an attractive route to responsive materials for advanced engineering, biomimetic and biomedical applications.}, number={16}, journal={MACROMOLECULES}, author={Shankar, Ravi and Krishnan, Arjun K. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2008}, month={Aug}, pages={6100–6109} }
 @article{peng_sun_spagnola_hyde_spontak_parsons_2007, title={Atomic layer deposition on electrospun polymer fibers as a direct route to Al2O3 microtubes with precise wall thickness control}, volume={7}, ISSN={["1530-6984"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000244867400032&KeyUID=WOS:000244867400032}, DOI={10.1021/nl062948i}, abstractNote={Atomic layer deposition (ALD) of Al2O3 on electrospun poly(vinyl alcohol) microfiber templates is demonstrated as an effective and robust strategy by which to fabricate long and uniform metal-oxide microtubes. The wall thickness is shown to be precisely controlled within a molecular layer or so by adjusting the number of ALD cycles utilized. By judicious selection of the electrospinning and ALD parameters, designer tubes of various sizes and inorganic materials can be synthesized.}, number={3}, journal={NANO LETTERS}, author={Peng, Qing and Sun, Xiao-Yu and Spagnola, Joseph C. and Hyde, G. Kevin and Spontak, Richard J. and Parsons, Gregory N.}, year={2007}, month={Mar}, pages={719–722} }
 @article{frankowski_khan_spontak_2007, title={Chain-scission-induced intercalation as a facile route to polymer nanocomposites}, volume={19}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200600793}, abstractNote={Immiscible polystyrene (PS)/clay nanocomposites undergo intercalation upon spatially tuned and atmosphere-regulated thermal-oxidative chain scission (see figure), with resultant increases in moduli and thermal stability. Shortened PS chains generated by scission predominantly locate in the clay galleries and not in the bulk where they would detrimentally affect mechanical properties.}, number={9}, journal={ADVANCED MATERIALS}, author={Frankowski, David J. and Khan, Saad A. and Spontak, Richard J.}, year={2007}, month={May}, pages={1286-+} }
 @misc{shankar_ghosh_spontak_2007, title={Dielectric elastomers as next-generation polymeric actuators}, volume={3}, ISSN={["1744-6848"]}, DOI={10.1039/b705737g}, abstractNote={Due to their versatile properties, robust behavior, facile processability and low cost, organic polymers have become the material of choice for an increasing number of mature and cutting-edge technologies. In the last decade or so, a new class of polymers capable of responding to external electrical stimulation by displaying significant size or shape change has emerged. These responsive materials, collectively referred to as electroactive polymers (EAPs), are broadly classified as electronic or ionic according to their operational mechanism. Electronic EAPs generally exhibit superior performance relative to ionic EAPs in terms of actuation strain, reliability, durability and response time. Among electronic EAPs, dielectric elastomers exhibit the most promising properties that mimic natural muscle for use in advanced robotics and smart prosthetics, as well as in haptic and microfluidic devices. Elastomers derived from homopolymers such as acrylics and silicones have received considerable attention as dielectric EAPs, whereas novel dielectric EAPs based on selectively swollen nanostructured block copolymers with composition-tailorable properties have only recently been reported. Here, we provide an overview of various EAPs in terms of their operational mechanisms, uses and shortcomings, as well as a detailed account of dielectric elastomers as next-generation actuators.}, number={9}, journal={SOFT MATTER}, author={Shankar, Ravi and Ghosh, Tushar K. and Spontak, Richard J.}, year={2007}, pages={1116–1129} }
 @article{shankar_ghosh_spontak_2007, title={Electroactive nanostructured polymers as tunable actuators}, volume={19}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200602644}, abstractNote={Lightweight and conformable electroactive actuators stimulated by low electric fields are required for emerging responsive technologies. In this work, we demonstrate that selectively swollen triblock copolymers yield electroactive nanostructured polymers (ENPs) that exhibit excellent displacement (>200% areal strain) under an applied electric field (see figure). Such ENPs possess properties that can be broadly tailored and represent a viable avenue to designer organic actuators for advanced engineering, biomimetic, and biomedical applications.}, number={17}, journal={ADVANCED MATERIALS}, author={Shankar, Ravi and Ghosh, Tushar K. and Spontak, Richard J.}, year={2007}, month={Sep}, pages={2218-+} }
 @article{shankar_ghosh_spontak_2007, title={Electromechanical response of nanostructured polymer systems with no mechanical pre-strain}, volume={28}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200700033}, abstractNote={A dielectric elastomer derived from a polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene triblock copolymer swollen with a midblock-selective solvent is reported to show promise as a nanostructured organic actuator requiring no pre-strain. This might provide an attractive alternative to conventional acrylic, siloxane, and polyurethane elastomers since the electromechanical properties are composition-tunable.}, number={10}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Shankar, Ravi and Ghosh, Tushar K. and Spontak, Richard J.}, year={2007}, month={May}, pages={1142–1147} }
 @article{sun_shankar_boerner_ghosh_spontak_2007, title={Field-driven biofunctionalization of polymer fiber surfaces during electrospinning}, volume={19}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200601345}, abstractNote={Surface-biofunctionalized synthetic polymer fibers composed of a fiber-forming host polymer and an oligopeptide conjugate are prepared by electrospinning. The conjugate consists of a polypeptide segment and a polymer block that is compatible with the host polymer. Because the more polarizable peptide segment migrates to the surface during electrospinning, peptide surface enrichment (see figure and inside cover) is achieved in a single step without further treatment.}, number={1}, journal={ADVANCED MATERIALS}, author={Sun, Xiao-Yu and Shankar, Ravi and Boerner, Hans G. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2007}, month={Jan}, pages={87-+} }
 @article{wang_wang_frankowski_lam_welch_winnik_hartmann_manners_spontak_2007, title={Growth and crystallization of metal-containing block copolymer nanotubes in a selective solvent}, volume={19}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200602230}, abstractNote={Highly asymmetric metal-containing block copolymers are capable of forming nanotubes in solutions containing a nonpolar solvent. In this study, the time-dependent formation of these nanotubes is investigated and reveals how the aggregate nanostructures develop (see figure for an example at an early stage). These nanotubes are semicrystalline (see the diffraction pattern in the inset), suggesting that crystallization is at least partially responsible for the unique morphology formed by these block copolymers.}, number={17}, journal={ADVANCED MATERIALS}, author={Wang, Xiaosong and Wang, Hai and Frankowski, David J. and Lam, Peter G. and Welch, Paul M. and Winnik, Mitchell A. and Hartmann, Juergen and Manners, Ian and Spontak, Richard J.}, year={2007}, month={Sep}, pages={2279-+} }
 @article{sun_shankar_börner_ghosh_spontak_2007, title={Inside Front Cover: Field-Driven Biofunctionalization of Polymer Fiber Surfaces during Electrospinning (Adv. Mater. 1/2007)}, volume={19}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.200790004}, DOI={10.1002/adma.200790004}, abstractNote={Surface-biofunctionalized synthetic polymer fibers composed of a fiber-forming host polymer and an oligopeptide conjugate can be prepared from electrospinning, report Spontak and co-workers on p. 87. The conjugate consists of a polypeptide segment and a polymer block that is compatible with the host polymer. Because the more polarizable peptide segment migrates to the surface during electrospinning, peptide surface-enrichment is achieved in a single step without further treatment.}, number={1}, journal={Advanced Materials}, publisher={Wiley}, author={Sun, X.-Y. and Shankar, R. and Börner, H. G. and Ghosh, T. K. and Spontak, R. J.}, year={2007}, month={Jan}, pages={NA-NA} }
 @article{guo_arends_thomann_spontak_gronski_2007, title={Morphological development and rheological changes of phenoxy/SAN blends during in-situ polymerization}, volume={45}, ISSN={["1099-0488"]}, DOI={10.1002/polb.21267}, abstractNote={This article reports the results of an investigation into the time-dependent morphological and rheological changes that accompany the in-situ polymerization of blends composed of poly(hydroxyether of bisphenol A) (phenoxy) and poly(styrene-co-acrylonitrile) (SAN). The rheological behavior was monitored continuously during the in-situ polymerization, whereas the miscibility and phase structure of blends formed in situ were examined at discrete stages of polymerization by differential scanning calorimetry and transmission electron microscopy. In the blend with 30 wt % SAN, a co-continuous blend morphology was associated with gradual changes in the dynamic moduli, suggesting that phase separation proceeded by spinodal decomposition (SD). In contrast, phenoxy-rich dispersions were uniformly dispersed in a continuous SAN-rich matrix in the blend with 50 wt % SAN, and the corresponding rheological signature revealed a sharp initial increase in the dynamic moduli, followed by slower growth after long times, indicative of phase separation via nucleation and growth (NG). The rheological property changes are closely related to morphology development and mechanisms of phase separation induced duringin-situ polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2614–2619, 2007}, number={18}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Guo, Qipeng and Arends, Peter and Thomann, Ralf and Spontak, Richard J. and Gronski, Wolfram}, year={2007}, month={Sep}, pages={2614–2619} }
 @article{gil_frankowski_hudson_spontak_2007, title={Silk fibroin membranes from solvent-crystallized silk fibroin/gelatin blends: Effects of blend and solvent composition}, volume={27}, ISSN={["0928-4931"]}, DOI={10.1016/j.msec.2006.05.017}, abstractNote={Protein membranes have been prepared by mixing gelatin (G) with Bombyx mori silk fibroin (SF) and using aqueous methanol (MeOH) to induce SF crystallization. Amorphous blends of these polymers appear quasi-homogeneous, as discerned from visual observation, electron microscopy and Fourier-transform infrared (FTIR) spectroscopy. Upon subsequent exposure to aqueous MeOH, SF undergoes a conformational change from random-coil to β-sheet. This transformation occurs in pure SF, as well as in each of the G/SF blends, as discerned from FTIR spectroscopy and thermal calorimetry. The influence of MeOH-induced SF crystallization on structure and property development has been measured as functions of blend and solvent composition. By preserving a support scaffold above the G helix-to-coil transition temperature, the formation of crystalline SF networks in G/SF blends can be used to stabilize G-based hydrogels or generate SF membranes for biomaterial, pharmaceutical and gas-separation purposes. The present study not only examines the properties of G/SF blends before and after SF crystallization, but also establishes the foundation for future research into thermally-responsive G/SF bioconjugates.}, number={3}, journal={MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS}, author={Gil, Eun S. and Frankowski, David J. and Hudson, Samuel M. and Spontak, Richard J.}, year={2007}, month={Apr}, pages={426–431} }
 @article{frankowski_capracotta_martin_khan_spontak_2007, title={Stability of organically modified montmorillonites and their polystyrene nanocomposites after prolonged thermal treatment}, volume={19}, ISSN={["0897-4756"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34250177310&partnerID=MN8TOARS}, DOI={10.1021/cm061953k}, abstractNote={Melt intercalation of montmorillonite (MMT) into polymeric matrices to improve the mechanical properties of polymers has evolved into a subject of tremendous fundamental and technological interest. The thermal treatment experienced during processing or end use can substantially affect the clay and diminish the target properties of polymer/clay nanocomposites (NCs) because of deintercalation or degradation of surface modifiers. In this work, changes in morphology, chemistry, and thermal stability of organically modified (OM) MMT after annealing in O2-rich and N2 environments are investigated. Degradation of the alkyl ammonium cation occurs at temperatures as low as 105 °C upon prolonged exposure in an O2-rich environment. X-ray diffractometry (XRD) performed in situ establishes the response of two OM-MMTs to elevated temperatures at short times, whereas ex situ XRD provides insight into high-temperature exposure at long times. Active sites on the silicate surfaces are found to induce scission of, as well as chemical interaction with, the chains comprising a polystyrene (PS) matrix. Size-exclusion chromatography indicates that PS chain scission occurs primarily after relatively short annealing times, whereas branching and cross-linking are more prevalent after long exposure times in an O2-rich environment.}, number={11}, journal={CHEMISTRY OF MATERIALS}, author={Frankowski, David J. and Capracotta, Michael D. and Martin, James D. and Khan, Saad A. and Spontak, Richard J.}, year={2007}, month={May}, pages={2757–2767} }
 @article{maynor_larue_hu_rolland_pandya_fu_liu_spontak_sheiko_samulski_et al._2007, title={Supramolecular nanomimetics: Replication of micelles, viruses, and other naturally occurring nanoscale objects}, volume={3}, ISSN={["1613-6810"]}, DOI={10.1002/smll.200600507}, abstractNote={Replicas of naturally occurring structures, including viruses (see image, left), micelles (center), and carbon nanotubes (right) are made from fluoropolymer molds templated from naturally occurring objects. The successful integration of imprint fabrication with bottom-up self-assembly is demonstrated for integrated nanopatterning, which may have applications in many diverse areas such as sensors, implantable biomaterials, and medical therapies. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2296/2007/z600507_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.}, number={5}, journal={SMALL}, author={Maynor, Benjamin W. and LaRue, Isaac and Hu, Zhaokang and Rolland, Jason P. and Pandya, Ashish and Fu, Qiang and Liu, Jie and Spontak, Richard J. and Sheiko, Sergei S. and Samulski, Richard J. and et al.}, year={2007}, month={May}, pages={845–849} }
 @article{jinnai_hasegawa_nishikawa_sevink_braunfeld_agard_spontak_2006, title={3D nanometer-scale study of coexisting bicontinuous morphologies in a block copolymer/homopolymer blend}, volume={27}, ISSN={["1521-3927"]}, DOI={10.1002/marc.200600344}, abstractNote={Summary: Coexisting bicontinuous morphologies, one ordered and one disordered, are investigated in a macrophase-separated poly(styrene-block-isoprene) diblock copolymer/homopolystyrene (SI/hS) blend. Two-phase behavior is attributed to the relatively high hS/S mass ratio (0.92). According to its crystallographic signature and channel coordination as discerned from three-dimensional (3D) images generated by transmission electron microtomography (TEMT), the ordered morphology is classified as gyroid. The 3D local and global topological characteristics of both bicontinuous morphologies as measured directly from TEMT images are reported. The disordered morphology is further compared with molecular-field simulations to ascertain the spatial distribution of the constituent species within the blend, thereby demonstrating the utility of high-resolution 3D imaging coupled with molecular-level simulations.}, number={17}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Jinnai, Hiroshi and Hasegawa, Hirokazu and Nishikawa, Yukihiro and Sevink, G. J. Agur and Braunfeld, Michael B. and Agard, David A. and Spontak, Richard J.}, year={2006}, month={Sep}, pages={1424–1429} }
 @article{jinnai_hasegawa_nishikawa_sevink_braunfeld_agard_spontak_2006, title={Front Cover: Macromol. Rapid Commun. 17/2006}, volume={27}, ISSN={1022-1336 1521-3927}, url={http://dx.doi.org/10.1002/marc.200690032}, DOI={10.1002/marc.200690032}, number={17}, journal={Macromolecular Rapid Communications}, publisher={Wiley}, author={Jinnai, Hiroshi and Hasegawa, Hirokazu and Nishikawa, Yukihiro and Sevink, G. J. Agur and Braunfeld, Michael B. and Agard, David A. and Spontak, Richard J.}, year={2006}, month={Sep}, pages={1401–1401} }
 @article{gil_frankowski_bowman_gozen_hudson_spontak_2006, title={Mixed protein mends composed of gelatin and bombyx mori silk fibroin: Effects of so solvent-induced crystallization and composition}, volume={7}, ISSN={["1526-4602"]}, DOI={10.1021/bm050622i}, abstractNote={Novel protein blends have been prepared by mixing gelatin (G) with Bombyx mori silk fibroin (SF) and using aqueous methanol (MeOH) to post-induce SF crystallization. When co-cast from solution, amorphous blends of these polymers appear homogeneous, as discerned from visual observation, microscopy, and Fourier-transform infrared (FTIR) spectroscopy. Upon subsequent exposure to aqueous MeOH, SF undergoes a conformational change from random coil to β sheet. This transformation occurs in pure SF, as well as in each of the G/SF blends, according to X-ray diffractometry and thermal calorimetry. The influence of MeOH-induced SF crystallization on structure and property development has been ascertained in terms of preparation history and blend composition. Thermal gravimetric analysis reveals that the presence of β sheets in SF and G/SF blends improves thermal stability, while extensional rheometry confirms that SF crystallization enhances the tensile properties of the blends. By preserving a support scaffold above the G helix-to-coil transition temperature, the formation of crystalline SF networks in G/SF blends can be used to stabilize G-based hydrogels for biomaterial and pharmaceutical purposes. The present study not only examines the properties of G/SF blends before and after SF crystallization, but also establishes the foundation for future research into thermally responsive G/SF bioconjugates.}, number={3}, journal={BIOMACROMOLECULES}, author={Gil, ES and Frankowski, DJ and Bowman, MK and Gozen, AO and Hudson, SM and Spontak, RJ}, year={2006}, month={Mar}, pages={728–735} }
 @article{smith_hamersky_bowman_rasmussen_spontak_2006, title={Molecularly asymmetric triblock copolymers as a single-molecule route to ordered bidisperse polymer brushes}, volume={22}, ISSN={["0743-7463"]}, DOI={10.1021/la060616n}, abstractNote={The conditions signaling the formation of bidisperse brushes in ordered block copolymers are investigated as an A2 block is progressively grown onto an A1B diblock copolymer to form a series of molecularly asymmetric, isomorphic A1BA2 triblock copolymers. Small-angle scattering and self-consistent field theory confirm that the microphase-ordered period decreases when the A2 block is short relative to the A1 block, but then increases as A1+A2 bidisperse brushes develop. The mechanical properties systematically follow the spatial distribution of the A2 block.}, number={15}, journal={LANGMUIR}, author={Smith, Steven D. and Hamersky, Mark W. and Bowman, Michelle K. and Rasmussen, Kim O. and Spontak, Richard J.}, year={2006}, month={Jul}, pages={6465–6468} }
 @article{spontak_shankar_bowman_krishnan_hamersky_samseth_bockstaller_rasmussen_2006, title={Selectivity- and size-induced segregation of molecular and nanoscale species in microphase-ordered triblock copolymers}, volume={6}, ISSN={["1530-6992"]}, DOI={10.1021/nl061205u}, abstractNote={Microphase-ordered block copolymers serve as model systems to elucidate the potential of molecular self-assembly and organic templates to fabricate functionalized polymeric materials. Both aspects are related to the incorporation of secondary species such as low-molar-mass compounds or nanoparticles within the copolymer matrices. Since the resulting properties of such functionalized copolymers critically depend on the morphology of the blend or composite, the nonrandom distribution of such inclusions within the copolymer matrix must be understood. Using a self-consistent field theoretical approach, we quantitatively evaluate the segregation and interfacial excess of low-molar-mass and nanoscale species in ordered triblock copolymers as functions of block selectivity and inclusion size. The predictions are found to agree with the morphology observed in a model triblock copolymer/nanoparticle composite, thereby demonstrating the generality of this approach. Our results suggest a wide correspondence in the structure-forming effect of molecular and nanoscale inclusions that will have implications in the design and processing of functional nanostructured polymers.}, number={9}, journal={NANO LETTERS}, author={Spontak, Richard J. and Shankar, Ravi and Bowman, Michelle K. and Krishnan, Arjun S. and Hamersky, Mark W. and Samseth, Jon and Bockstaller, Michael R. and Rasmussen, Kim O.}, year={2006}, month={Sep}, pages={2115–2120} }
 @article{spontak_braunfeld_agard_jinnai_2006, title={Transmission Electron Microtomography (TEMT) of Nanostructured Polymers under Dynamically Evolving Conditions}, volume={12}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927606069509}, DOI={10.1017/S1431927606069509}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005}, number={S02}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Spontak, RJ and Braunfeld, MB and Agard, DA and Jinnai, H}, year={2006}, month={Jul}, pages={182–183} }
 @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{siripurapu_desimone_khan_spontak_2005, title={Controlled foaming of polymer films through restricted surface diffusion and the addition of nanosilica particles or CO2-philic surfactants}, volume={38}, ISSN={["1520-5835"]}, DOI={10.1021/ma047991b}, abstractNote={Synergistic use of surface barriers and nanoscale additives is investigated as alternate means by which to promote bubble nucleation in, and thus improve the porosity of, poly(methyl methacrylate) (PMMA) thin films (i) constrained between impenetrable plates, (ii) modified with either nanosilica particles, commercial short-chain fluorosurfactants, or designer CO2-philic block/graft copolymers, and (iii) exposed to high-pressure CO2. Resultant foamed films exhibit a vast array of micro/mesocellular morphologies in the presence of supercritical, as well as liquid, CO2 and demonstrate that copolymer micelles afford better control over bubble nucleation (with pore cell densities, N, approaching 1012 cells/cm3) relative to hard nonporous nanoparticles, which alone increase N by more than 2 orders of magnitude at low CO2 pressures. Incorporation of these nanoscale additives in a surface-constrained polymer matrix serves to enhance foaming through concurrent restriction of CO2 diffusion, heterogeneous nucleation of CO2 bubbles, and/or reduced interfacial tension between PMMA and CO2.}, number={6}, journal={MACROMOLECULES}, author={Siripurapu, S and DeSimone, JM and Khan, SA and Spontak, RJ}, year={2005}, month={Mar}, pages={2271–2280} }
 @article{gil_spontak_hudson_2005, title={Effect of beta-sheet crystals on the thermal and rheological behavior of protein-based hydrogels derived from gelatin and silk fibroin}, volume={5}, ISSN={["1616-5187"]}, DOI={10.1002/mabi.200500076}, abstractNote={Summary: Novel protein-based hydrogels have been prepared by blending gelatin (G) with amorphous Bombyx mori silk fibroin (SF) and subsequently promoting the formation of β-sheet crystals in SF upon exposure to methanol or methanol/water solutions. Differential scanning calorimetry of the resultant hydrogels confirms the presence and thermoreversibility of the G helix-coil transition between ambient and body temperature at high G concentrations. At low G concentrations, this transition is shifted to higher temperatures and becomes progressively less pronounced. Complementary dynamic rheological measurements reveal solid-liquid cross-over at the G helix-coil transition temperature typically between 30 and 36 °C in blends prior to the formation of β-sheet crystals. Introducing the β-sheet conformation in SF stabilizes the hydrogel network and extends the solid-like behavior of the hydrogels to elevated temperatures beyond body temperature with as little as 10 wt.-% SF. The temperature-dependent elastic modulus across the G helix-coil transition is reversible, indicating that the conformational change in G can be used in stabilized G/SF hydrogels to induce thermally triggered encapsulant release. Thermally reversible helix-coil conformational transition of gelatin in mixed gelatin/silk fibroin hydrogels.}, number={8}, journal={MACROMOLECULAR BIOSCIENCE}, author={Gil, ES and Spontak, RJ and Hudson, SM}, year={2005}, month={Aug}, pages={702–709} }
 @article{harton_stevie_spontak_koga_rafailovich_sokolov_ade_2005, title={Low-temperature reactive coupling at polymer–polymer interfaces facilitated by supercritical CO2}, volume={46}, ISSN={0032-3861}, url={http://dx.doi.org/10.1016/j.polymer.2005.07.085}, DOI={10.1016/j.polymer.2005.07.085}, abstractNote={Supercritical CO2 (scCO2) has been used to facilitate reactions in thin film bilayers between functionalized polystyrene and poly(methyl methacrylate) at temperatures far below the glass transition temperatures of the respective polymers. Secondary ion mass spectrometry (SIMS) is used to monitor the reaction progression directly by measuring the interfacial excess of deuterated PS. Complementary X-ray reflectometry (XR) yields the interfacial width and surface roughness of bilayer films for reactive systems with and without the addition of scCO2, and comparisons are made with unreactive reference systems. From XR and SIMS analyses, the interfacial width and roughness have been found to be effectively independent of the reaction conditions employed here, and the primary impact of incorporated scCO2 is enhanced mobility of the reactive polymer chains. The use of scCO2 can change polymer mobility significantly enough over a very small temperature range (DTw15 8C) so that both diffusion- and reaction-controlled type behavior can be observed for otherwise identical systems. q 2005 Elsevier Ltd. All rights reserved.}, number={23}, journal={Polymer}, publisher={Elsevier BV}, author={Harton, S.E. and Stevie, F.A. and Spontak, R.J. and Koga, T. and Rafailovich, M.H. and Sokolov, J.C. and Ade, H.}, year={2005}, month={Nov}, pages={10173–10179} }
 @article{hamersky_smith_gozen_spontak_2005, title={Phase behavior of triblock copolymers varying in molecular asymmetry}, volume={95}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.95.168306}, abstractNote={The transformation from ${A}_{1}B$ diblock copolymer to ${A}_{1}B{A}_{2}$ triblock copolymers varying in molecular asymmetry is investigated as the ${A}_{2}$ end block is progressively grown via chemical synthesis. Dynamic rheological measurements show that the order-disorder transition (ODT) temperatures of two copolymer series differing in composition and molecular weight decrease when the ${A}_{2}$ block is short relative to the ${A}_{1}$ block, and then increase as the length of the ${A}_{2}$ block is increased further. The resultant ODT minimum, predicted by mean-field theory, is attributed to mixing between long $B$ and short ${A}_{2}$ blocks.}, number={16}, journal={PHYSICAL REVIEW LETTERS}, author={Hamersky, MW and Smith, SD and Gozen, AO and Spontak, RJ}, year={2005}, month={Oct} }
 @article{van maanen_seeley_capracotta_white_bukovnik_hartmann_martin_spontak_2005, title={Property and Morphology Development in Nanocomposite Thermoplastic Elastomer Gels}, volume={21}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/la047837i}, DOI={10.1021/la047837i}, abstractNote={Thermoplastic elastomer gels (TPEGs), molecular networks composed of a microphase-separated multiblock copolymer swollen to a large extent by a low-volatility midblock-selective solvent, are ubiquitous in a wide range of contemporary technologies, including home and office products, athletic equipment, and telecommunications devices. In this work, we investigate the effect of several network-forming nanoscale modifiers-two different silica nanoparticles, three different nanoclays, and a multiwalled carbon nanotube-on the property and morphology development of a TPEG prepared from a microphase-ordered poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) triblock copolymer imbibed with an EB-compatible aliphatic mineral oil. Dynamic rheological measurements of the resultant nanocomposite TPEGs confirm that addition of these modifiers affects the linear viscoelastic threshold and increases, to different extents, the dynamic elastic modulus, the dynamic yield stress, and the maximum operating temperature of the parent TPEG. X-ray diffraction analysis reveals that the nanoclays used to generate three series of modified TPEGs are generally swollen with copolymer and/or solvent.}, number={7}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={van Maanen, Guillermo J. and Seeley, Sabrina L. and Capracotta, Michael D. and White, Scott A. and Bukovnik, Rudolf R. and Hartmann, Jürgen and Martin, James D. and Spontak, Richard J.}, year={2005}, month={Mar}, pages={3106–3115} }
 @article{gil_frankowski_spontak_hudson_2005, title={Swelling behavior and morphological evolution of mixed gelatin/silk fibroin hydrogels}, volume={6}, ISSN={["1526-4602"]}, DOI={10.1021/bm050396c}, abstractNote={Mixed protein-based hydrogels have been prepared by blending gelatin (G) with amorphous Bombyx mori silk fibroin (SF) and promoting β-crystallization of SF via subsequent exposure to methanol or methanol/water solutions. The introduction of β crystals in SF serves to stabilize the hydrogel network and extend the solidlike behavior of these thermally responsive materials to elevated temperatures beyond the helix→coil (h→c) transition of G. In this work, we investigate the swelling and protein release kinetics of G/SF hydrogels varying in composition at temperatures below and above the G h→c transition. At 20 °C, G and G-rich mixed hydrogels display evidence of moderate swelling with negligible mass loss in aqueous solution, resulting in porous polymer matrixes upon solvent removal according to electron microscopy. When the solution temperature is increased beyond the G h→c transition to body temperature (37 °C), these gels exhibit much higher swelling with considerable mass loss due to dissolution and release of G. The extent to which these properties respond to temperature decreases systematically with increasing SF content. The unique temperature- and composition-dependent properties of G/SF hydrogels dictate the efficacy of these novel materials as stimuli-responsive delivery vehicles.}, number={6}, journal={BIOMACROMOLECULES}, author={Gil, ES and Frankowski, DJ and Spontak, RJ and Hudson, SM}, year={2005}, pages={3079–3087} }
 @article{spontak_gozen_braunfeld_agard_2005, title={Transmission Electron Microtomography (TEMT) of Nanostructured Polymers and Polymer Nanocomposites}, volume={11}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927605510341}, DOI={10.1017/S1431927605510341}, number={S02}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Spontak, R J and Gozen, A O and Braunfeld, M B and Agard, D A}, year={2005}, month={Aug} }
 @article{patel_hunt_lin-gibson_bencherif_spontak_2005, title={Tunable CO2 transport through mixed polyether membranes}, volume={251}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2004.11.003}, abstractNote={Gas-separation membranes composed of polyethers such as poly(ethylene glycol)diacrylate (PEGda) or poly(propylene glycol)diacrylate (PPGda) exhibit high CO2 solubility selectivity, which makes them attractive for use in H2 and air purification. In this work, we investigate the factors governing CO2 and H2 transport in mixed polyether matrices. Addition of semicrystalline poly(ethylene oxide)s to amorphous PEGda lowers the net CO2 permeability and CO2/H2 selectivity due to crystal formation. Gas permeation through the amorphous fraction, however, remains unaffected, confirming the existence of a molecular weight limit below which the entire membrane participates in gas transport. The permeabilities of CO2 and H2, as well as their activation energy of permeation, in miscible PEGda/PPGda blends follow the linear rule of mixtures over the temperature range explored. Incorporation of amine moieties employed in liquid membranes into either the PEGda matrix during crosslinking or the PEG backbone generally reduces CO2/H2 selectivity but occasionally improves CO2 permeability.}, number={1-2}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Patel, NP and Hunt, MA and Lin-Gibson, S and Bencherif, S and Spontak, RJ}, year={2005}, month={Apr}, pages={51–57} }
 @misc{spontak_2004, title={Book review: Block Copolymers. Synthetic Strategies, Physical Properties, and Applications. By Nikos Hadjichristidis, Stergios Pispas, and George A. Floudas.}, volume={16}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.200490009}, DOI={10.1002/adma.200490009}, abstractNote={Advanced MaterialsVolume 16, Issue 4 p. 367-368 Book Review Book review: Block Copolymers. Synthetic Strategies, Physical Properties, and Applications. By Nikos Hadjichristidis, Stergios Pispas, and George A. Floudas. R. J. Spontak, R. J. SpontakSearch for more papers by this author R. J. Spontak, R. J. SpontakSearch for more papers by this author First published: 26 February 2004 https://doi.org/10.1002/adma.200490009Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume16, Issue4February, 2004Pages 367-368 RelatedInformation}, number={4}, journal={Advanced Materials}, publisher={Wiley}, author={Spontak, R. J.}, year={2004}, month={Feb}, pages={367–368} }
 @article{frankowski_fournier-bidoz_manners_ozin_khan_spontak_2004, title={Cover Picture: Macromol. Chem. Phys. 18/2004}, volume={205}, ISSN={1022-1352 1521-3935}, url={http://dx.doi.org/10.1002/macp.200490043}, DOI={10.1002/macp.200490043}, number={18}, journal={Macromolecular Chemistry and Physics}, publisher={Wiley}, author={Frankowski, David J. and Fournier-Bidoz, S�bastien and Manners, Ian and Ozin, Geoffrey A. and Khan, Saad A. and Spontak, Richard J.}, year={2004}, month={Dec}, pages={2381–2381} }
 @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 ∼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={ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTDewetting of Star Nanogel/Homopolymer Blends from an Immiscible Homopolymer SubstrateBin Wei, Paul A. Gurr, Jan Genzer, Greg G. Qiao, David H. Solomon, and Richard J. SpontakView Author Information Departments of Chemical & Biomolecular Engineering 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, Australia Cite this: Macromolecules 2004, 37, 21, 7857–7860Publication Date (Web):October 12, 2004Publication History Received6 July 2004Revised26 August 2004Published online12 October 2004Published inissue 1 October 2004https://doi.org/10.1021/ma048636oCopyright © 2004 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views333Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (155 KB) Get e-AlertsSUBJECTS:Dewetting,Interfaces,Layers,Nanoparticles,Organic compounds Get e-Alerts}, 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{patel_zielinski_samseth_spontak_2004, title={Effects of pressure and nanoparticle functionality on CO2-selective nanocomposites derived from crosslinked poly(ethylene glycol)}, volume={205}, ISSN={["1521-3935"]}, DOI={10.1002/macp.200400356}, abstractNote={Summary: Purification of H2 generated from industrial gasification processes requires removal of CO2 as the permeate from mixed CO2/H2 streams to avoid costly H2 repressurization. Such gas separation can be achieved through the use of reverse-selective polymer membranes that exhibit high CO2 affinity. In this work, the physical properties of CO2-selective membranes composed of poly(ethylene glycol) diacrylate (PEGda), as well as PEGda nanocomposites with 10 wt.-% fumed silica (FS), are reported. Two PEGda oligomers differing in chain length and FS nanoparticles varying in surface functionality are exposed to CO2 at low and high pressures to elucidate the roles of CO2 pressure, network topology and nanoparticle aggregation on molecular transport and solubility. Results from swelling and sorption kinetics confirm that both penetrant diffusivity and solubility increase with increasing PEGda chain length and decreasing network density. Methacrylate-terminated FS nanoparticles are more effective in improving rheological properties and retaining high CO2 selectivity than hydroxyl-terminated nanoparticles of comparable size. TGA profiles obtained from crosslinked PEGda membranes and their corresponding nanocomposites: PEGda575 (•), PEGda575 with 10 wt.-% FSma (▴), PEGda700 (○), and PEGda700 with 10 wt.-% FSma (▵).}, number={18}, journal={MACROMOLECULAR CHEMISTRY AND PHYSICS}, author={Patel, NP and Zielinski, JM and Samseth, J and Spontak, RJ}, year={2004}, month={Dec}, pages={2409–2419} }
 @article{frankowski_raez_manners_winnik_khan_spontak_2004, title={Formation of dispersed nanostructures from poly(ferrocenyldimethylsilane-b-dimethylsiloxane) nanotubes upon exposure to supercritical carbon dioxide}, volume={20}, ISSN={["0743-7463"]}, DOI={10.1021/la049646l}, abstractNote={While incompatible block copolymers commonly assemble into several established classical or complex morphologies, highly asymmetric poly(ferrocenyldimethylsilane-b-dimethylsiloxane) (PFS-b-PDMS) diblock copolymers can also self-organize into high-aspect-ratio nanotubes with PDMS corona in the presence of PDMS-selective organic solvents. Exposure of these nanotubes on a carbon substrate to supercritical carbon dioxide (scCO2), also a PDMS-selective solvent, appears to promote partial dissolution of the copolymer molecules. At sufficiently high copolymer concentrations, the dissolved molecules subsequently re-organize within the scCO2 environment to form new copolymer nanostructures that redeposit on the substrate upon scCO2 depressurization. Transmission electron microscopy reveals that micelles form under all the conditions examined here, whereas nanotubes coalesce and vesicles develop only at relatively high temperatures. The extent to which the copolymer nanotubes dissolve and the size distribution of the replacement micelles are sensitive to exposure conditions. These results suggest that the phase behavior of PFS-b-PDMS diblock copolymers in scCO2 may be remarkably rich and easily tunable.}, number={21}, journal={LANGMUIR}, author={Frankowski, DJ and Raez, J and Manners, I and Winnik, MA and Khan, SA and Spontak, RJ}, year={2004}, month={Oct}, pages={9304–9314} }
 @article{patel_spontak_2004, title={Gas-transport and thermal properties of a microphase-ordered poly(styrene-b-ethylene oxide-b-styrene) triblock copolymer and its blends with poly(ethylene glycol)}, volume={37}, ISSN={["0024-9297"]}, DOI={10.1021/ma049975k}, abstractNote={Block copolymers are under growing consideration as precursor materials for use in a wide variety of emerging nanotechnologies. While these materials can serve as ordered templates in the preparation of nanoporous membranes, they can also be designed for use as dense nanostructured polymer membranes exhibiting chemical specificity. In the present work, we explore the properties of a poly(styrene-b-ethylene oxide-b-styrene) (SEOS) triblock copolymer and its blends with poly(ethylene glycol) (PEG) as reverse-selective membranes due to their unusually high CO2 affinity. The permeability of CO2 measured as a function of blend composition, PEG molecular weight, and temperature is consistently found to exceed that of any other gas (H2, N2, or O2) examined here. Addition of PEG eventually results in a composition-dependent transition from an alternating lamellar to polyether-continuous morphology, as evidenced by both gas-transport and thermal properties, and a systematic variation in crystallinity that depends on PEG molecular weight. Since the microphase-ordered copolymer morphology remains intact up to temperatures higher than the polyether melting temperature, the changes in permeability that occur upon polyether melting can be directly measured.}, number={8}, journal={MACROMOLECULES}, author={Patel, NP and Spontak, RJ}, year={2004}, month={Apr}, pages={2829–2838} }
 @article{patel_miller_spontak_2004, title={Highly CO2-permeable and -selective membranes derived from crossfinked poly(ethylene glycol) and its nanocomposites}, volume={14}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.200305136}, abstractNote={Crosslinked poly(ethylene glycol diacrylate) (PEGda) oligomers differing in molecular weight, and their nanocomposites prepared with up to 10 wt.-% methacrylate-functionalized fumed silica (FS) or an organically-modified nanoclay, have been examined as amorphous CO2-selective membranes. These novel materials have been characterized by dynamic rheology before and after crosslinking to ascertain the effect of incorporated FS on mechanical properties. The permeabilities of CO2, H2, N2, and O2 have been measured as functions of PEGda molecular weight, nanofiller content and temperature. In all cases, CO2 displays relatively high permeability, coupled with high CO2 selectivity, due to the specific interaction between quadrupolar CO2 and the ether linkages along the PEG backbone, and the accompanying enhancement in CO2 solubility. Variable-temperature permeation exhibits Arrhenius behavior, and the activation energy for CO2 permeation is found to be i) markedly lower than that of any of the other gases examined, and ii) independent of both PEGda molecular weight and nanofiller content.}, number={7}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Patel, NP and Miller, AC and Spontak, RJ}, year={2004}, month={Jul}, pages={699–707} }
 @article{siripurapu_desimone_khan_spontak_2004, title={Low-temperature, surface-mediated foaming of polymer films}, volume={16}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200306068}, abstractNote={Ultraporous thin polymer films (see Figure) are generated using physical constraints imposed by external surfaces (hard plates) and internal surfaces (hard nanoparticles and soft micelles) via foaming with supercritical CO2. The constraints serve as diffusion barriers and/or heterogeneous nucleation sites. Use of CO2-philic copolymers further enables microcellular foaming at reduced pressures with liquid CO2.}, number={12}, journal={ADVANCED MATERIALS}, author={Siripurapu, S and DeSimone, JM and Khan, SA and Spontak, RJ}, year={2004}, month={Jun}, pages={989-+} }
 @article{patel_spontak_2004, title={Mesoblends of polyether block copolymers with poly(ethylene glycol)}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma0356257}, abstractNote={Mesoblends are conveniently generated by sorbing a parent homopolymer into a microphase-separated triblock or higher-order multiblock copolymer swollen by a block-selective solvent. These nonequilibrium systems afford a viable route by which to produce, in systematic fashion, novel copolymer/homopolymer blends as well as explore homopolymer transport and solubility within a molecularly confined polymer environment. In the present work, we have imbibed poly(ethylene glycol) (PEG) differing in molecular weight into a model poly(styrene-b-ethylene oxide-b-styrene) (SEOS) triblock copolymer and a commercial poly(amide-b-ethylene glycol) (AEG) multiblock copolymer. Solvent quality and solution concentration are found to have a profound effect on PEG solubility in both copolymers, whereas PEG molecular weight over the range 100−4600 is generally less influential. Transmission electron microscopy reveals the spatial distribution of amorphous PEG within the SEOS copolymer matrix, and complementary differential scanning calorimetry establishes the role of added PEG on the thermal behavior of the copolymer midblock. Incorporation of PEG into the AEG copolymer serves to improve the CO2/H2 selectivity of this material at ambient temperature and low pressure.}, number={4}, journal={MACROMOLECULES}, author={Patel, NP and Spontak, RJ}, year={2004}, month={Feb}, pages={1394–1402} }
 @misc{desimone_khan_royer_spontak_walker_gay_siripurapu_2004, title={Methods of making foamed materials of blended thermoplastic polymers using carbon dioxide}, volume={6,790,870}, number={2004 Sept. 14}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={DeSimone, J. M. and Khan, S. A. and Royer, J. R. and Spontak, R. J. and Walker, T. A. and Gay, Y. J. and Siripurapu, S.}, year={2004} }
 @article{patel_aberg_sanchez_capracotta_martin_spontak_2004, title={Morphological, mechanical and gas-transport characteristics of crosslinked poly(propylene glycol): homopolymers, nanocomposites and blends}, volume={45}, ISSN={["1873-2291"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-3342879397&partnerID=MN8TOARS}, DOI={10.1016/j.polymer.2004.06.024}, abstractNote={Linear polyethers possess unusually high CO2 solubility and, hence, selectivity due to the presence of accessible ether linkages that can interact with the quadrupolar moment of CO2 molecules. In this work, membranes derived from crosslinked poly(propylene glycol) diacrylate (PPGda) oligomers differing in molecular weight (M), as well as PPGda nanocomposites containing either an organically-modified montmorillonite clay or a methacrylate-terminated fumed silica are investigated and compared with highly CO2-selective poly(ethylene glycol) diacrylate (PEGda) homopolymer and nanocomposite membranes previously reported. The rheological and permeation properties of PPGda depend sensitively on M, with the elastic modulus decreasing, but CO2 permeability and CO2/H2 selectivity increasing, with increasing M. Incorporation of either nanofiller into PPGda enhances the elastic modulus and reduces the gas permeability in the resultant nanocomposites without strongly affecting CO2/H2 selectivity. Blending PPGda and PEGda prior to chemical crosslinking yields binary membranes that exhibit intermediate gas-transport properties accurately described by a linear rule of mixtures.}, number={17}, journal={POLYMER}, author={Patel, NP and Aberg, CM and Sanchez, AM and Capracotta, MD and Martin, JD and Spontak, RJ}, year={2004}, month={Aug}, pages={5941–5950} }
 @article{shtykova_svergun_chernyshov_khotina_valetsky_spontak_bronstein_2004, title={Platinum nanoparticles generated in functionality-enhanced reaction media based on polyoctadecylsiloxane with long-chain functional modifiers}, volume={108}, ISSN={["1520-6106"]}, DOI={10.1021/jp049336b}, abstractNote={Functionality-enhanced nanostructured matrices generated by intercalating polyoctadecylsiloxane (PODS) with octadecene (ODC) or octadecylamine (ODA) are employed as reaction media in which to grow Pt nanoparticles. Small-angle X-ray scattering (SAXS) signatures confirm that the amphiphilic PODS matrix orders into lamellae with a periodicity (d) of 5.24 nm, which corresponds to the siloxy bilayer and a double layer of alkyl tails. The regular packing of the hydrophobic tails becomes distorted upon introduction of ODC or ODA. Incorporation of K[(C2H4)PtCl3]·H2O (a Zeise salt) into the PODS/ODC matrix, followed by reduction of the Pt ions by NaBH4 or H2, results in the localization of Pt compounds and nanoparticles along the siloxy bilayers, which remain dimensionally unchanged. Electron density profiles deduced from PODS/ODA, however, provide evidence for considerable structural reorganization upon metalation with H2PtCl6·6H2O. In this case, the siloxy bilayers broaden due to the presence of PtCl62- ions, and the hydrophobic layers become distorted due to the formation of (PtCl62-)(ODAH+)2 complexes. Subsequent reduction by NaBH4 restores the inherent PODS organization, while H2 reduction partially preserves the distorted matrix, indicating that some Pt nanoparticles form in close proximity to the siloxy bilayer. Transmission electron microscopy reveals that relatively monodisperse Pt nanoparticles measuring ∼1 nm in diameter are located along the siloxy bilayers, whereas anomalous SAXS further indicates that nanoparticles form aggregates of comparable size to d within the PODS double layers.}, number={20}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Shtykova, EV and Svergun, DI and Chernyshov, DM and Khotina, IA and Valetsky, PM and Spontak, RJ and Bronstein, LM}, year={2004}, month={May}, pages={6175–6185} }
 @article{power-billard_spontak_manners_2004, title={Redox-active organometallic vesicles: Aqueous self-assembly of a diblock copolymer with a hydrophilic polyferrocenylsilane polyelectrolyte block}, volume={43}, ISSN={["1521-3773"]}, DOI={10.1002/anie.200352819}, number={10}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Power-Billard, KN and Spontak, RJ and Manners, I}, year={2004}, pages={1260–1264} }
 @article{bronstein_goerigk_kostylev_pink_khotina_valetsky_matveeva_sulman_sulman_bykov_et al._2004, title={Structure and catalytic properties of Pt-modified hyper-cross-linked polystyrene exhibiting hierarchical porosity}, volume={108}, ISSN={["1520-6106"]}, DOI={10.1021/jp046459n}, abstractNote={The structural transformation and catalytic properties of metal/polymer nanocomposites derived from hyper-cross-linked polystyrene (HPS) exhibiting both microporosity and macroporosity, and filled with Pt nanoparticles, are investigated in the direct oxidation of l-sorbose to 2-keto-l-gulonic acid. Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, anomalous small-angle X-ray scattering, and catalytic studies suggest that the catalytically active species, nanoparticles of mixed composition with a mean diameter of 1.6 nm, develop after the initial induction period. At the highest selectivity (96.8%) at 100% l-sorbose conversion, the catalytic activity is measured to be 2.5 × 10-3 mol/mol Pt-s, which corresponds to a 4.6-fold increase in activity relative to the Pt-modified microporous HPS previously reported. This substantial increase in catalytic activity is attributed to the presence of macropores, which facilitate mass transport and, consequently, accessibility of the nanoparticle surface for reactants.}, number={47}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Bronstein, LM and Goerigk, G and Kostylev, M and Pink, M and Khotina, IA and Valetsky, PM and Matveeva, VG and Sulman, EM and Sulman, MG and Bykov, AV and et al.}, year={2004}, month={Nov}, pages={18234–18242} }
 @article{siripurapu_coughlan_spontak_khan_2004, title={Surface-constrained foaming of polymer thin films with supercritical carbon dioxide}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma0484983}, abstractNote={Microcellular polymer foams afford a wide variety of attributes relative to their dense analogues, and efforts remain underway to establish viable routes to generate foams with substantially reduced pore cell size and increased pore cell density. Barrier constraints are applied in the present work to achieve diffusion-controlled isothermal foaming of thin polymer films in the presence of supercritical carbon dioxide (scCO2). Poly(methyl methacrylate) (PMMA) films measuring ca. 95−100 μm in thickness are physically constrained between two impenetrable plates so that scCO2 exit diffusion is restricted to the film edges. Results obtained here demonstrate that the pore size can be systematically reduced to less than 100 nm in such systems by applying high saturation scCO2 pressures, relatively low foaming temperatures (near the glass transition temperature of the scCO2-plasticized polymer), and a rapid pressure quench. Classical nucleation theory (CNT) modified to account for the compressible nature of scCO2 is used to describe pore cell growth as a function of foaming temperature and scCO2 saturation pressure. Incorporation of a gradient model based on the Sanchez−Lacombe equation of state to account for PMMA−CO2 interfacial tension in conjunction with the CNT yields accurate predictions of foam cell densities as a function of relevant system parameters.}, number={26}, journal={MACROMOLECULES}, author={Siripurapu, S and Coughlan, JA and Spontak, RJ and Khan, SA}, year={2004}, month={Dec}, pages={9872–9879} }
 @article{walker_colina_gubbins_spontak_2004, title={Thermodynamics of poly(dimethylsiloxane)/poly(ethylmethylsiloxane) (PDMS/PEMS) blends in the presence of high-pressure CO2}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma034920o}, abstractNote={Processing polymer blends in the presence of high-pressure carbon dioxide (CO2) affords numerous advantages over organic solvents and is becoming a commercially viable and environmentally responsible alternative in the development of new multicomponent materials. A prerequisite to such processing is a fundamental understanding of how high-pressure CO2 influences the phase behavior of polymer blends. In this work, we use high-pressure spectrophotometry to measure the cloud point (Tcp) of poly(dimethylsiloxane)/poly(ethylmethylsiloxane) (PDMS/PEMS) blends as a function of CO2 pressure (P) in the vapor phase. Results obtained here at different blend compositions indicate that values of Tcp for this upper critical solution temperature (UCST) blend (i) generally increase with increasing pressure and (ii) collapse onto a master curve of ΔTcp(P) for pressures up to about 35 MPa. These data are analyzed by the Sanchez−Lacombe equation of state to ascertain the temperature dependence of an effective interaction parameter (χ) in terms of A + B/T, where A and B are both pressure-sensitive. We also compare our results with previously reported data to delineate the role of hydrostatic pressure on the phase behavior of these blends.}, number={7}, journal={MACROMOLECULES}, author={Walker, TA and Colina, CM and Gubbins, KE and Spontak, RJ}, year={2004}, month={Apr}, pages={2588–2595} }
 @article{frankowski_fournier-bidoz_manners_ozin_khan_spontak_2004, title={Tunable microcellular morphologies from poly (ferrocenylsilane) ceramic precursors foamed in supercritical CO(2)}, volume={205}, ISSN={["1022-1352"]}, DOI={10.1002/macp.200400333}, abstractNote={Summary: Poly(ferrocenylmethylphenylsilane) (PFMPS) and poly[ferrocenylmethyl(phenylacetylido)silane] (PFMPAS) homopolymers are organometallic polymers that can serve as precursors to magnetically-active ceramics. In this work, PFMPS and PFMPAS films ranging in thickness from 30 to 220 μm have been exposed to scCO2 over a broad range of saturation pressures, temperatures and times to produce surface-constrained microcellular polymeric foams. Electron microscopy identifies viable foaming windows and reveals that foams with submicron cell sizes can be generated by judicious selection of exposure conditions. Cell shape anisotropy can likewise be varied from being nearly spherical to vertically elongated. Curvature in the films and non-negligible surface roughness create paths that facilitate CO2 diffusion, resulting in the formation of “V-directional” cells oriented at approximately 30° to the film surface. The development of bimodal cell size distributions is attributed to temperature variation during depressurization and/or stepwise homogeneous and heterogeneous nucleation. These results are prerequisite for the production of magnetically-active porous ceramics from pyrolyzed PFS foams. SEM image of a PFMPS foam generated in scCO2 illustrating considerable cell anisotropy: the cells are tilted with respect to the film surface.}, number={18}, journal={MACROMOLECULAR CHEMISTRY AND PHYSICS}, author={Frankowski, DJ and Fournier-Bidoz, SB and Manners, I and Ozin, GA and Khan, SA and Spontak, RJ}, year={2004}, month={Dec}, pages={2398–2408} }
 @article{walls_riley_fedkiw_spontak_baker_khan_2003, title={Composite electrolytes from self-assembled colloidal networks}, volume={48}, ISSN={["0013-4686"]}, DOI={10.1016/S0013-4686(03)00187-7}, abstractNote={Abstract In this study, we present two approaches to developing composite electrolytes exploiting the self-assembling nature of colloidal fillers. The first system comprises of oligomers of poly(ethylene glycol) dimethyl ether, branched fumed silica particulates and lithium salt. The fumed silica forms a three-dimensional, self-supporting network that provides mechanical stability. The large pores of the network has little effect on diffusivity of ions and oligomers, lithium transference number and ionic conductivity, with the latter showing values >10 −3 S/cm at ambient conditions. The second system consists of Li exchanged hectorite clay in a mixture of low molar mass carbonates. Similar to the fumed silica, the clay provides mechanical stability through formation of a three-dimensional network. In addition, the immobile clay platelets also serve as the anion rendering the system to be a single ion conductor. Near-unity transference number is observed in this case. However, the room temperature conductivity of the clay composite is lower than the fumed silica, revealing a value of about 10 −4 S/cm. The lower conductivity can be attributed to the clay not being in a fully exfoliated form as evident from morphological analysis.}, number={14-16}, journal={ELECTROCHIMICA ACTA}, author={Walls, HJ and Riley, MW and Fedkiw, PS and Spontak, RJ and Baker, GL and Khan, SA}, year={2003}, month={Jun}, pages={2071–2077} }
 @article{bronstein_linton_karlinsey_ashcraft_stein_svergun_kozin_khotina_spontak_werner-zwanziger_et al._2003, title={Controlled synthesis of novel metalated poly(aminohexyl)-(aminopropyl)silsesquioxane colloids}, volume={19}, ISSN={["0743-7463"]}, DOI={10.1021/la034291b}, abstractNote={A new family of polysilsesquioxanes colloids was synthesized by hydrolytic condensation of a functionalized precursor N-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS), H2N(CH2)6NHCH2CH2CH2Si(OCH3)3, and studied using small-angle X-ray scattering, transmission electron microscopy, liquid and solid state NMR, elemental analysis, and other methods. The PAHAPS (polymerized AHAPS) structure is highly functionalized and its functionality can be varied by protonation of the amino groups. This allows varying the local ordering in the PAHAPS colloids, including formation of highly ordered lamellar structures when the AHAPS precursor is hydrolyzed in pure water. By varying the type of solvent (water or THF), one can vary the macrostructure and properties (for example, to impart colloidal solubility) of PAHAPS. These features make PAHAPS a robust polymer material synthesized in a one-pot reaction procedure. As amino groups (protonated or not) easily interact with the majority of transition-metal compounds, PAHAPS colloids can template a variety of particles of interest: magnetic, semiconductor, metal, or metal oxides with a small variation in the synthetic procedure. Here, formation of narrowly distributed discrete Pt nanoparticles packed within PAHAPS colloids (Pt content reaching 36 wt % without particle agglomeration) is described. The dependence of Pt nanoparticle and PAHAPS colloid sizes on metal compound and reducing agent types is demonstrated.}, number={17}, journal={LANGMUIR}, author={Bronstein, LM and Linton, CN and Karlinsey, R and Ashcraft, E and Stein, BD and Svergun, DI and Kozin, M and Khotina, IA and Spontak, RJ and Werner-Zwanziger, U and et al.}, year={2003}, month={Aug}, pages={7071–7083} }
 @article{wilder_hall_khan_spontak_2003, title={Effects of composition and matrix polarity on network development in organogels of poly(ethylene glycol) and dibenzylidene sorbitol}, volume={19}, ISSN={["0743-7463"]}, DOI={10.1021/la027081s}, abstractNote={Dibenzylidene sorbitol (DBS) is a low-molecular-weight organic molecule that can gel a variety of organic solvents and polymers by self-organizing into a three-dimensional nanofibrillar network through hydrogen-bonding and phenyl interactions. In this work, we investigate the composition dependence of such “organogels” prepared with poly(ethylene glycol) (PEG) and two PEG derivatives differing in methoxy end- group substitution, which serves to reduce matrix polarity. Transmission electron microscopy reveals that individual DBS nanofibrils measure from about 10 to 70 nm in diameter, with a primary nanofibrillar diameter of about 10 nm. Dynamic rheological measurements indicate that the rate by which the elastic modulus increases during gelation, the temperatures corresponding to gel formation and dissolution, and the magnitude of the elastic modulus are all sensitive to the DBS mass concentration (φ) and the matrix polarity. Hydroxy-end-capped PEG/DBS systems gel more slowly, but dissolve faster, than their methoxy-end-capped analogues at constant φ. The elastic modulus, however, is less dependent on matrix polarity and scales as φ1.8 over the range of φ examined in PEG/DBS organogels. Time−temperature superposition analysis provides direct evidence for the activation energy of network evolution increasing linearly with (i) decreasing φ at constant matrix polarity and (ii) increasing matrix polarity at constant φ.}, number={15}, journal={LANGMUIR}, author={Wilder, EA and Hall, CK and Khan, SA and Spontak, RJ}, year={2003}, month={Jul}, pages={6004–6013} }
 @article{wilder_white_smith_spontak_2003, title={Gel network development inn AB, ABA, and AB/ABA block copolymer solutions inn a selective solvent}, volume={833}, DOI={10.1021/bk-2002-0833.ch017}, abstractNote={In the presence of a selective solvent, ordered block copolymers form micelles that, at sufficiently high copolymer concentrations, serve to stabilize a three-dimensional network and promote physical gelation. This study examines the steady and dynamic rheological properties of micellar solutions composed of AB diblock, ABA triblock and bidisperse mixtures of AB and ABA copolymer molecules. Of particular interest is the unexpected improvement in network development upon addition of an AB copolymer to an ABA copolymer at constant solution composition. This behavior is observed for ABA/solvent systems above and below the critical gelation concentration, and is interpreted in terms of the volume exclusion that occurs in bidisperse mixture of grafted chains.}, journal={Polymer gels: Fundamentals and applications}, publisher={Washington, D.C.: American Chemical Society}, author={Wilder, E. A. and White, S. A. and Smith, S. D. and Spontak, Richard}, editor={H. B. Bohidar, P. Dubin and Osada, Y.Editors}, year={2003}, pages={248–261} }
 @article{patel_miller_spontak_2003, title={Highly CO2-permeable and selective polymer nanocomposite membranes}, volume={15}, ISSN={["0935-9648"]}, DOI={10.1002/adma.200304712}, abstractNote={As technologies turn to more efficient routes to remove CO2 from mixed gas streams for H2 or air purification, new cost-effective multifunctional materials are needed for the separation processes. Here, hybrid poly(ethylene glycol)/fumed silica nanocomposite membranes exhibiting high CO2/H2 selectivity (> 11) and CO2 permeability (∼ 83 Barrer), as well as robust mechanical properties and optical clarity, are reported (see Figure).}, number={9}, journal={ADVANCED MATERIALS}, author={Patel, NP and Miller, AC and Spontak, RJ}, year={2003}, month={May}, pages={729–733} }
 @article{oliveira_hirsch_spontak_gehrke_2003, title={Influence of polymer conformation on the shear modulus and morphology of polyallylamine and poly(alpha-L-lysine) hydrogels}, volume={36}, ISSN={["1520-5835"]}, DOI={10.1021/ma021468k}, abstractNote={Two polyamines with different conformational properties, poly(α-l-lysine) and polyallylamine, were chemically cross-linked to evaluate the effects of polypeptide secondary structures on gel properties. Both cationic gels are highly swollen at low pH and shrink as it increases primarily due to the reduction in of the concentration of associated counterions in the gel as its ionization decreases. Network shear moduli were determined under uniaxial compression. For the polyallylamine gels, the shear modulus (G) scales as φ20.31, where φ2 denotes the polymer volume fraction, over the entire pH range. This result is in favorable agreement with the G ∼ φ21/3 relationship predicted for networks of flexible chains. Poly(α-l-lysine) gels swollen below pH 11.0 obey the same scaling behavior. At higher pH levels, however, organized secondary structures are believed to develop, and the composition dependence of the modulus at high pH becomes consistent with the scaling relationship predicted for rigid-rod chain netwo...}, number={16}, journal={MACROMOLECULES}, author={Oliveira, ED and Hirsch, SG and Spontak, RJ and Gehrke, SH}, year={2003}, month={Aug}, pages={6189–6201} }
 @article{walls_riley_singhal_spontak_fedkiw_khan_2003, title={Nanocomposite electrolytes with fumed silica and hectorite clay networks: Passive versus active fillers}, volume={13}, ISSN={["1616-301X"]}, DOI={10.1002/adfm.200304333}, abstractNote={The use of nanocomposites constitutes a versatile and robust approach in the development of novel electrolytes with tailored electrochemical and mechanical characteristics. In this study, we examine the morphology, rheology, and ion-transport properties of two types of nanocomposite electrolyte gels, one consisting of branched silica nanoparticles and the other composed of hectorite clay. In the first system with hydrophobic (fumed) silica, oligomers of poly(ethylene oxide) (PEO), and lithium salt, the silica acts as a passive filler and does not participate in ion transport. The electrochemical properties are controlled by the salt–PEO electrolyte, allowing for ionic conductivities greater than 10–3 S cm–1 at ambient temperature. At sufficiently high concentrations, the silica forms an elastic gel possessing a large open network structure that provides for unimpeded ion mobility. In the second system composed of lithium-exchanged hectorite filler, the nanoscale platelets serve as the anion. This active filler yields ionic conductivities in excess of 10–4 S cm–1 and lithium transference numbers approaching unity. Similar to fumed silica, the hectorite clay also forms an elastic gel network. However, the morphologies of the two systems are distinctively different both in terms of network structure and characteristic length scale. These morphological differences manifest themselves in different rheological responses with regard to gel modulus and yield stress.}, number={9}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Walls, HJ and Riley, MW and Singhal, RR and Spontak, RJ and Fedkiw, PS and Khan, SA}, year={2003}, month={Sep}, pages={710–717} }
 @article{wilder_braunfeld_jinnai_hall_agard_spontak_2003, title={Nanofibrillar networks in poly(ethyl methacrylate) and its silica nanocomposites}, volume={107}, ISSN={["1520-6106"]}, DOI={10.1021/jp035113u}, abstractNote={Recent advances in polymer materials design seek to incorporate functionality, enhance existing properties, and reduce weight without compromising mechanical properties or processability. While much attention has been drawn to the development of organic/inorganic hybrid nanocomposites modified with discrete siliceous nanoparticles (such as fumed/colloidal silica or organoclays), other opportunities exist for comparably enlightened materials design. Dibenzylidene sorbitol (DBS) is a sugar derivative that is capable of self-organizing into a 3D nanofibrillar network at relatively low concentrations in a wide variety of organic solvents and polymers. In this work, we explore the morphological characteristics and properties of DBS in poly(ethyl methacrylate) (PEMA) and PEMA nanocomposites with colloidal silica. Transmission electron microscopy and microtomography reveal that the DBS molecules form highly connected networks, with nanofibrils measuring ca. 10 nm in diameter and ranging up to several hundred nanometers in length. Dynamic mechanical property analysis reveals that, while DBS has little effect on glassy PEMA, it serves to increase the elastic modulus in molten PEMA.}, number={42}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Wilder, EA and Braunfeld, MB and Jinnai, H and Hall, CK and Agard, DA and Spontak, RJ}, year={2003}, month={Oct}, pages={11633–11642} }
 @article{walker_melnichenko_wignall_lin_spontak_2003, title={Phase behavior of poly(methyl methacrylate)/poly(vinylidene fluoride) blends in the presence of high-pressure carbon dioxide}, volume={204}, ISSN={["1521-3935"]}, DOI={10.1002/macp.200350075}, abstractNote={Previous efforts have demonstrated that high-pressure CO2 can markedly influence the phase behavior of amorphous polymer blends. In this work, we examine the effect of high-pressure CO2 on the miscibility of blends composed of glassy poly(methyl methacrylate) (PMMA) and semicrystalline poly(vinylidene fluoride) (PVDF). Blends of this type are known to exhibit lower critical solution temperature (LCST) behavior with partial miscibility up to ≈50–60 wt.-% PVDF at ambient conditions. Two miscible PMMA/PVDF blends have been systematically exposed to high-pressure CO2 at 35 °C and pressures below and above the critical pressure. Small-angle X-ray scattering reveals that the scattering intensity at high scattering angles shows little dependence on pressure at low CO2 pressures, but increases substantially at relatively high CO2 pressures. Transmission electron microscopy and differential scanning calorimetry analyses confirm that the blends are initially quasi-homogeneous with diffuse PVDF-rich dispersions and a single glass transition temperature. After exposure to relatively high CO2 pressures, however, the PVDF is found to crystallize within the PMMA-rich matrix. Thermal recycling of these blends promotes homogenization, indicating that such CO2-altered phase behavior is reversible. SAXS patterns acquired from the 69/31 w/w PMMA/PVDF blend.}, number={17}, journal={MACROMOLECULAR CHEMISTRY AND PHYSICS}, author={Walker, TA and Melnichenko, YB and Wignall, GD and Lin, JS and Spontak, RJ}, year={2003}, month={Nov}, pages={2064–2077} }
 @article{walker_melnichenko_wignall_spontak_2003, title={Phase behavior of poly(methyl methacrylate)/poly(vinylidene fluoride) blends with and without high-pressure CO2}, volume={36}, ISSN={["0024-9297"]}, DOI={10.1021/ma030103c}, abstractNote={ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTPhase Behavior of Poly(methyl methacrylate)/Poly(vinylidene fluoride) Blends with and without High-Pressure CO2Teri A. Walker, Yuri B. Melnichenko, George D. Wignall, and Richard J. SpontakView Author Information Departments of Chemical Engineering and Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695, and Condensed Matter Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 Cite this: Macromolecules 2003, 36, 12, 4245–4249Publication Date (Web):May 23, 2003Publication History Received11 February 2003Published online23 May 2003Published inissue 1 June 2003https://doi.org/10.1021/ma030103cCopyright © 2003 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views347Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (86 KB) Get e-AlertsSUBJECTS:Differential scanning calorimetry,Fluoropolymers,Organic compounds,Polymers,Scattering Get e-Alerts}, number={12}, journal={MACROMOLECULES}, author={Walker, TA and Melnichenko, YB and Wignall, GD and Spontak, RJ}, year={2003}, month={Jun}, pages={4245–4249} }
 @article{wilder_hall_spontak_2003, title={Physical organogels composed of amphiphilic block copolymers and 1,3 : 2,4-dibenzylidene-D-sorbitol}, volume={267}, ISSN={["0021-9797"]}, DOI={10.1016/S0021-9797(03)00619-2}, abstractNote={The 1,3:2,4-dibenzylidene-D-sorbitol (DBS) molecule is capable of self-organizing into nanoscale fibrils through intermolecular forces such as hydrogen bonding and pi interactions. At sufficiently high concentrations (typically less than approximately 2 wt%), the nanofibrils can form a network that promotes physical gelation of the matrix medium. Previous studies have investigated the mechanism of DBS-induced gelation and the features of DBS-containing gels in poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG). In this work, we examine the effect of adding DBS to a series of amphiphilic PPG-b-PEG-b-PPG triblock copolymers differing in composition and molecular weight. Dynamic rheological measurements reveal that the resultant gels are thermoreversible (i.e., they exhibit comparable mechanical properties before dissolution and after reformation under quiescent conditions), exhibiting a maximum in the elastic modulus (G') at temperatures near the gel dissolution (T(d)) and formation (T(f)) temperatures. Both T(d) and T(f) tend to increase with increasing DBS concentration and PPG content, and their difference decreases with increasing PPG fraction in the copolymer. The magnitude of G' is sensitive to copolymer composition and polymer identity at low DBS concentrations, but becomes polymer-independent as the DBS network saturates at concentrations in excess of approximately 1 wt%.}, number={2}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Wilder, EA and Hall, CK and Spontak, RJ}, year={2003}, month={Nov}, pages={509–518} }
 @article{stevens_thongruang_patel_smith_spontak_2003, title={Solvent-facilitated homopolymer sorption in swollen block copolymer matrices}, volume={36}, ISSN={["1520-5835"]}, DOI={10.1021/ma0215868}, abstractNote={Homopolymer sorption in microphase-ordered block copolymers can provide insight into the factors governing transport of chain molecules in dense nanostructured environments, as well as yield novel nonequilibrium materials. Here, we examine the sorption of homopolymer B (hB) in ABA triblock copolymers swollen in a B-selective solvent. Gravimetric analysis reveals that the solubility of hB (ShB) varies linearly with solution concentration (C) and that (∂ShB/∂C)T depends on the molecular weight of the B midblock (MB). These data also show that the effective diffusion coefficient of hB is ∼10-8 cm2/s, independent of MB.}, number={9}, journal={MACROMOLECULES}, author={Stevens, JE and Thongruang, W and Patel, NP and Smith, SD and Spontak, RJ}, year={2003}, month={May}, pages={3206–3209} }
 @article{merkel_freeman_spontak_he_pinnau_meakin_hill_2003, title={Sorption, transport, and structural evidence for enhanced free volume in poly(4-methyl-2-pentyne)/fumed silica nanocomposite membranes}, volume={15}, ISSN={["0897-4756"]}, DOI={10.1021/cm020672j}, abstractNote={In contrast to the performance of traditional filled polymer systems, penetrant permeability coefficients in high-free-volume, glassy poly(4-methyl-2-pentyne) (PMP) increase systematically and substantially with increasing concentration of nonporous, nanoscale fumed silica (FS). For instance, the permeability of PMP containing 40 wt % FS to methane is 2.3 times higher than that of the unfilled polymer. Gas and vapor uptake in the PMP/FS nanocomposites is essentially unaffected by the presence of up to 40 wt % FS, while penetrant diffusion coefficients increase regularly with increasing filler content. This increase in diffusivity is responsible for elevated permeability in the PMP/FS nanocomposites. The addition of FS to PMP augments the permeability of large penetrants more than that of small gases, consistent with a reduction in diffusivity selectivity. Consequently, vapor selectivity in the nanocomposites increases with increasing FS concentration. Activation energies of permeation in PMP decrease with increasing FS content, suggesting that penetrant diffusive jumps require less energy at higher filler concentrations. Positron annihilation lifetime spectroscopy (PALS) reveals that FS subtly increases the free volume in PMP available for molecular transport. The accessible free volume measured by PALS correlates favorably with relative penetrant permeability in the nanocomposites. Transmission electron microscopy confirms that the FS nanoparticles are relatively well dispersed in PMP.}, number={1}, journal={CHEMISTRY OF MATERIALS}, author={Merkel, TC and Freeman, BD and Spontak, RJ and He, Z and Pinnau, I and Meakin, P and Hill, AJ}, year={2003}, month={Jan}, pages={109–123} }
 @article{gurr_qiao_solomon_harton_spontak_2003, title={Synthesis, characterization, and direct observation of star microgels}, volume={36}, ISSN={["0024-9297"]}, DOI={10.1021/ma030122m}, abstractNote={The molecular sizes of four star microgels, synthesized by atom transfer radical polymerization of poly(methyl methacrylate) (PMMA) with ethylene glycol dimethacrylate as the cross-linker, have been investigated by light scattering methods and transmission electron microscopy (TEM). Gel permeation chromatography right-angle laser light scattering performed with a triple detector system and dynamic light scattering together confirm that individual particles of one star microgel in tetrahydrofuran and styrene solutions possess mean diameters of 31 and 18 nm, respectively. Complementary TEM reveals that another star microgel appears as discrete particles measuring 18-30 nm in diameter when added to styrene monomer subsequently polymerized to form a solid matrix. These particles likewise undergo macrophase separation to form microgel-rich domains consisting of nanoscale PMMA channels. Additional TEM examination of a star microgel deposited by dilute solution casting provides direct evidence for the existence of individual microgel molecules with a mean (dry) diameter of ∼15 nm.}, number={15}, journal={MACROMOLECULES}, author={Gurr, PA and Qiao, GG and Solomon, DH and Harton, SE and Spontak, RJ}, year={2003}, month={Jul}, pages={5650–5654} }
 @article{wilder_spontak_hall_2003, title={The  molecular structure and intermolecular interactions of 1,3: 2,4-dibenzylidene-D-sorbitol}, volume={101}, DOI={10.1080/0268970310001597327}, number={19}, journal={Molecular Physics}, author={Wilder, E. A. and Spontak, Richard and Hall, C. K.}, year={2003}, pages={3017–3027} }
 @article{wilder_spontak_hall_2003, title={The molecular structure and intermolecular interactions of 1,3:2,4-dibenzylidene-D-sorbitol}, volume={101}, ISSN={0026-8976 1362-3028}, url={http://dx.doi.org/10.1080/00268970310001597327}, DOI={10.1080/00268970310001597327}, abstractNote={The 1,3(R):2,4(S)-dibenzylidene-D-sorbitol (DBS) molecule is a low molar mass organic gelator (LMOG) that is capable of hydrogen-bonding with itself. As a consequence, DBS molecules self-organize into nanofibrillar networks at relatively low concentrations in a wide variety of organic solvents and polymers. In this work, molecular mechanics and molecular dynamics simulations were conducted to elucidate the equilibrium structure of DBS and the molecular interactions that govern DBS self-assembly. Molecular mechanics calculations performed on single DBS molecules with Cerius2 and InsightII software reveal that the phenyl rings tend to adopt an equatorial position and that the pendant hydroxyl group prefers to form an intramolecular hydrogen bond with an acetal oxygen, in contrast to the terminal hydroxyl group. Molecular mechanics and molecular dynamics on DBS dimers reveal that they are capable of forming hydrogen bonds and participating in π interactions, suggesting that the mechanism of nanofibrillar network formation may be complex, involving more than one type of physical interaction.}, number={19}, journal={Molecular Physics}, publisher={Informa UK Limited}, author={Wilder, Elizabeth A. and Spontak, Richard J. and Hall, Carol K.}, year={2003}, month={Oct}, pages={3017–3027} }
 @article{walker_semler_leonard_maanen_bukovnik_spontak_2002, title={ABA triblock copolymer gels modified with an A-compatible semicrystalline homopolymer}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la026117d}, abstractNote={In the presence of a midblock-selective solvent, ABA triblock copolymers form physical gels in which bridged and entangled B-chains establish a swollen network stabilized by A-microdomains. Here, we seek to improve the properties of an ABA gel through the addition of an A-compatible, high-molecular-weight semicrystalline homopolymer (shA). Dynamic rheology indicates that the elastic modulus increases substantially, and far beyond that achievable with an inert filler, with increasing shA content at constant solvent concentration. Transmission electron micrographs reveal the existence of nanoscale shA filaments and sheets dispersed in a micelle-stabilized gel network. The shape of the nanoscale shA objects, which are partially crystalline according to differential scanning calorimetry, and their apparent interaction with the A-rich micelles enhance network development and are responsible for the pronounced modulus increase.}, number={22}, journal={LANGMUIR}, author={Walker, TA and Semler, JJ and Leonard, DN and Maanen, GJ and Bukovnik, RR and Spontak, RJ}, year={2002}, month={Oct}, pages={8266–8270} }
 @article{roberge_patel_white_thongruang_smith_spontak_2002, title={Block copolymer/homopolymer mesoblends: Preparation and characterization}, volume={35}, ISSN={["1520-5835"]}, DOI={10.1021/ma0115747}, abstractNote={Miscible block copolymer/homopolymer blends are typically prepared from homogeneous solutions in a nonselective solvent. During solvent removal and subsequent annealing, the molecular species comprising such blends organize in such fashion as to lower the system free energy and ideally attain thermodynamic equilibrium. In this work, we investigate nonequilibrium triblock copolymer/homopolymer (ABA/hB) blends generated by diffusing hB molecules from a hB-selective solvent into a lamellar ABA copolymer. Since the copolymer is already microphase-ordered during homopolymer incorporation, we refer to such blends as mesoblends. The mass uptake of hB is found to be strongly dependent on homopolymer molecular weight (MhB), with the maximum solubility scaling as MhB-1. An induction period that scales as MhB1/2 is also observed. Transmission electron microscopy reveals that the morphology of these mesoblends appears to be perforated lamellar, which, in some cases, transforms to cylindrical upon annealing. Dynamic mechanical analysis and differential scanning calorimetry confirm that the A-rich microdomains in the mesoblends are plasticized. The mechanical properties of these mesoblends can be improved upon annealing, but nonetheless differ from those of composition-matched conventional blends.}, number={6}, journal={MACROMOLECULES}, author={Roberge, RL and Patel, NP and White, SA and Thongruang, W and Smith, SD and Spontak, RJ}, year={2002}, month={Mar}, pages={2268–2276} }
 @article{thongruang_spontak_balik_2002, title={Bridged double percolation in conductive polymer composites: an electrical conductivity, morphology and mechanical property study}, volume={43}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(02)00180-5}, abstractNote={Conductive polymer composites are ubiquitous in technological applications and constitute an ongoing topic of tremendous commercial interest. Strategies developed to improve the level of electrical conductivity achieved at a given filler concentration have relied on double-percolated networks induced by immiscible polymer blends, as well as mixtures of fillers in a single polymer matrix, to enhance interparticle connectivity. In this work, we combine these two strategies by examining quaternary composites consisting of high-density polyethylene (HDPE), ultrahigh molecular weight polyethylene (UHMWPE), graphite (G) and carbon fiber (CF). On the basis of our previous findings, we examine the electrical conductivity, morphology, thermal signature and mechanical properties of HDPE/UHMWPE/G systems that show evidence of double percolation. Upon addition of CF, tremendous increases in conductivity are realized. The mechanism by which this increase occurs is termed bridged double percolation to reflect the role of CF in spanning non-conductive regions and enhancing the continuity of conductive pathways. At CF concentrations above the percolation threshold concentration, addition of G promotes increases in conductivity and dynamic storage modulus in which the conductivity increases exponentially with increasing modulus.}, number={13}, journal={POLYMER}, author={Thongruang, W and Spontak, RJ and Balik, CM}, year={2002}, month={Jun}, pages={3717–3725} }
 @article{thongruang_spontak_balik_2002, title={Correlated electrical conductivity and mechanical property analysis of high-density polyethylene filled with graphite and carbon fiber}, volume={43}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(02)00043-5}, abstractNote={The development of conductive polymer composites remains an important endeavor in light of growing energy concerns. In the present work, graphite (G), carbon fiber (CF) and G/CF mixtures are added to high-density polyethylene (HDPE) to discern if mixed fillers afford appreciable advantages over single fillers. The effects of filler type and composition on electrical conductivity, composite morphology and mechanical properties have been examined and correlated to establish structure–property relationships. The threshold loading levels required for G and CF to achieve measurable conductivity in HDPE have been identified. Addition of CF to HDPE/G composites is found to increase the conductivity relative to that of HDPE/G composites at the same filler concentration. This observed increase depends on CF length and becomes more pronounced at and beyond the threshold loading of the HDPE/G composite. Scanning electron microscopy is employed to elucidate the morphology of these multicomponent composites, whereas dynamic mechanical analysis reveals that filler concentration, composition and CF length impact both the magnitude and temperature dependence of the dynamic storage modulus.}, number={8}, journal={POLYMER}, author={Thongruang, W and Spontak, RJ and Balik, CM}, year={2002}, month={Apr}, pages={2279–2286} }
 @article{siripurapu_gay_royer_desimone_spontak_khan_2002, title={Generation of microcellular foams of PVDF and its blends using supercritical carbon dioxide in a continuous process}, volume={43}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(02)00407-X}, abstractNote={Abstract Use of supercritical carbon dioxide (scCO 2 ) as a blowing agent to generate microcellular polymer foams (MPFs) has recently received considerable attention due to environmental concerns associated with conventional organic blowing agents. While such foams derived from amorphous thermoplastics have been previously realized, semicrystalline MPFs have not yet been produced in a continuous scCO 2 process. This work describes the foaming of highly crystalline poly(vinylidene fluoride) (PVDF) and its blends with amorphous polymers during extrusion. Foams composed of neat PVDF and immiscible blends of PVDF with polystyrene exhibit poor cell characteristics, whereas miscible blends of PVDF with poly(methyl methacrylate) (PMMA) yield foams possessing vastly improved morphologies. The results reported herein illustrate the effects of blend composition and scCO 2 solubility on PVDF/PMMA melt viscosity, which decreases markedly with increasing PMMA content and scCO 2 concentration. Morphological characterization of microcellular PVDF/PMMA foams reveals that the cell density increases as the PMMA fraction is increased and the foaming temperature is decreased. This study confirms that novel MPFs derived continuously from semicrystalline polymers in the presence of scCO 2 can be achieved through judicious polymer blending.}, number={20}, journal={POLYMER}, author={Siripurapu, S and Gay, YJ and Royer, JR and DeSimone, JM and Spontak, RJ and Khan, SA}, year={2002}, month={Sep}, pages={5511–5520} }
 @article{english_laurer_spontak_khan_2002, title={Hydrophobically modified associative polymer solutions: Rheology and microstructure in the presence of nonionic surfactants}, volume={41}, ISSN={["0888-5885"]}, DOI={10.1021/ie020409s}, abstractNote={We report on the rheology and morphology of a hydrophobically modified alkali-swellable emulsion (HASE) polymer solubilized in alkaline media containing nonionic surfactants. The HASE polymer consists of complex alkylaryl hydrophobes composed of oligomeric nonylphenol condensates attached to a poly(ethyl acrylate-co-methacrylic acid) backbone. The complex linear viscoelastic response of the polymer in alkaline solution suggests an unentangled network with an appreciable fraction of microgel. The concentration and hydrophile−lipophile balance (HLB) of nonionic surfactants profoundly affect the solution rheology. A surfactant of high HLB inhibits the dynamic network connectivity of the HASE polymer, as demonstrated by reductions of both the steady-shear viscosity and the dynamic storage modulus. The shear-induced structuring previously reported for this polymer is also progressively diminished as the surfactant concentration is increased. In contrast, the addition of a low-HLB surfactant promotes system structuring, as evidenced by (i) increases in the shear viscosity and the high-frequency plateau modulus and (ii) retention of the ability to undergo shear-induced structuring. We also employ cryofracture-replication transmission electron microscopy for the first time with regard to HASE associative polymers to examine the morphological characteristics of selected systems. The morphology of the HASE polymer in both latex and solubilized form appears more complex than previously anticipated, and a reasonable interpretation of these new data is provided.}, number={25}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={English, RJ and Laurer, JH and Spontak, RJ and Khan, SA}, year={2002}, month={Dec}, pages={6425–6435} }
 @misc{desimone_khan_royer_spontak_walker_2002, title={Method of making foamed materialsUSing surfactants and carbon dioxide}, volume={6,403,663}, number={2002 Jun. 11}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={DeSimone, J. M. and Khan, S. A. and Royer, J. R. and Spontak, R. J. and Walker, T. A.}, year={2002} }
 @article{arnold_nagai_spontak_freeman_leroux_betts_desimone_digiano_stebbins_linton_et al._2002, title={Microphase-Separated Block Copolymers Comprising Low Surface Energy Fluorinated Blocks and Hydrophilic Blocks:  Synthesis and Characterization}, volume={35}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ma0119631}, DOI={10.1021/ma0119631}, abstractNote={The synthesis and characterization of diblock and triblock copolymers produced by a two-component iniferter system is reported. These materials, designed for possible water treatment applications, consist of a hydrophilic poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) block and a very low surface energy poly(1,1‘-dihydroperfluorooctyl methacrylate) (PFOMA) or poly(1,1,2,2-tetrahydroperfluorooctyl acrylate) (PTAN) block. Angle-dependent X-ray spectroscopy results and water contact angle measurements indicate that the surfaces of PDMAEMA-b-PFOMA diblock copolymers consist primarily of PFOMA. Transmission electron microscopy reveals that the block copolymers are microphase-separated, exhibiting either cylindrical or layered morphologies that do not change appreciably upon exposure to water. Both water uptake and water flux increase with increasing PDMAEMA content.}, number={9}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Arnold, M. E. and Nagai, K. and Spontak, Richard and Freeman, B. D. and Leroux, D. and Betts, D. E. and Desimone, J. M. and Digiano, F. A. and Stebbins, C. K. and Linton, R. W. and et al.}, year={2002}, month={Apr}, pages={3697–3707} }
 @article{leonard_russell_smith_spontak_2002, title={Multiscale dewetting of low-molecular-weight block copolymer ultrathin films}, volume={23}, ISSN={["1022-1336"]}, DOI={10.1002/1521-3927(20020201)23:3<205::AID-MARC205>3.0.CO;2-X}, abstractNote={Ultrathin films of a low-molecular-weight block copolymer spontaneously dewet after several days at ambient temperature. Film rupture produces macroscopic holes and a residual pancake brush layer ≈ 2 nm thick with intermittent mounds measuring up to 25 nm in thickness. Multiscale dewetting likewise occurs when the films are heated and returned to ambient temperature. Regardless of the surface pattern that forms during heating, submicron mounds develop on the dewetted copolymer film, and fine holes emerge along the substrate surface, after cooling.}, number={3}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Leonard, DN and Russell, PE and Smith, SD and Spontak, RJ}, year={2002}, month={Feb}, pages={205–209} }
 @article{bronstein_linton_karlinsey_stein_svergun_zwanziger_spontak_2002, title={Synthesis of metal-loaded poly(aminohexyl)(aminopropyl)silsesquioxane colloids and their self-organization into dendrites}, volume={2}, ISSN={["1530-6992"]}, DOI={10.1021/nl025543g}, abstractNote={Hydrolytic condensation of N-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS) in water results in the formation of spherical colloids measuring 40 to 190 nm in diameter and composed of a nearly fully condensed poly(aminohexyl)(aminopropyl)silsesquioxane (PAHAPS) nanostructure containing C−SiO3/2 species. Interaction of Pt and Pd salts with these PAHAPS colloids, followed by chemical reduction, results in the formation of discrete metal nanoparticles measuring ca. 1−2 nm in diameter stabilized within the colloids. Dendrites differing in size and shape are observed to form from aqueous solutions containing PAHAPS colloids loaded with metal salts or metal nanoparticles.}, number={8}, journal={NANO LETTERS}, author={Bronstein, LM and Linton, C and Karlinsey, R and Stein, B and Svergun, DI and Zwanziger, JW and Spontak, RJ}, year={2002}, month={Aug}, pages={873–876} }
 @article{hirsch_spontak_2002, title={Temperature-dependent property development in hydrogels derived from hydroxypropylcellulose}, volume={43}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(01)00608-5}, abstractNote={Hydrogels constitute an important class of responsive materials that are employed in numerous biomedical and personal-care applications, most notably of which are controlled drug delivery, separations and superabsorbency. Since aqueous hydroxypropylcellulose (HPC) solutions exhibit lower critical solution behavior, hydrogels produced from this cellulose ether are temperature-responsive, swelling at low temperatures and contracting at high temperatures. If HPC hydrogels are synthesized at temperatures in the single-phase regime, they remain nonporous, whereas those crosslinked in the biphasic regime become microporous. In this work, we employ the modified temperature-induced phase separation (TIPS) protocol to generate nonporous and microporous HPC hydrogels crosslinked at different temperatures. The dynamic mechanical properties and swelling capacities of these hydrogels are reported as functions of crosslinking temperature.}, number={1}, journal={POLYMER}, author={Hirsch, SG and Spontak, RJ}, year={2002}, month={Jan}, pages={123–129} }
 @article{leonard_spontak_smith_russell_2002, title={Topological coarsening of low-molecular-weight block copolymer ultrathin films by environmental AFM}, volume={43}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(02)00640-7}, abstractNote={Abstract Topological coarsening of block copolymer ultrathin films is well-understood for copolymers exhibiting intermediate or strong segregation and differing in film thickness or molecular weight at temperatures above the upper glass transition temperature ( T g ), but below the order–disorder transition ( T ODT ), of the copolymers. More recent studies suggest that the stability and topology of such films differ at temperatures above T ODT . In this work, we use environmental atomic force microscopy to examine the effect of temperature on the coarsening of block copolymer ultrathin films in situ. Films measuring ca. 25 nm thick consist of a low-molecular-weight poly(styrene- b -isoprene) diblock copolymer for which the upper T g and T ODT in the bulk are about 42 and 70 °C, respectively. Time-resolved image sequences illustrating surface reorganization are obtained at temperatures below, above and near 70 °C. At temperatures very close to 70 °C, coarsening is found to slow markedly, by almost an order of magnitude relative to what is observed at higher and lower temperatures, suggesting that thermal factors may provide a means by which to inhibit the dewetting of block copolymer ultrathin films.}, number={25}, journal={POLYMER}, author={Leonard, DN and Spontak, RJ and Smith, SD and Russell, PE}, year={2002}, month={Dec}, pages={6719–6726} }
 @article{jinnai_nishikawa_ito_smith_agard_spontak_2002, title={Topological similarity of sponge-like bicontinuous morphologies differing in length scale}, volume={14}, ISSN={["1521-4095"]}, DOI={10.1002/1521-4095(20021118)14:22<1615::AID-ADMA1615>3.0.CO;2-S}, abstractNote={Sponge-like bicontinuous morphologies (see Figure and also cover) are ubiquitous in the physical and biological sciences, but are only qualitatively understood in terms of their structure. Here, 3D imaging techniques are used to explore the characteristics of such morphologies at the nanoscale, microscale, and macroscale. Comparison of local and global topology metrics provides quantitative evidence of similarities between these morphologies.}, number={22}, journal={ADVANCED MATERIALS}, author={Jinnai, H and Nishikawa, Y and Ito, M and Smith, SD and Agard, DA and Spontak, RJ}, year={2002}, month={Nov}, pages={1615–1618} }
 @article{merkel_freeman_spontak_he_pinnau_meakin_hill_2002, title={Ultrapermeable, reverse-selective nanocomposite membranes}, volume={296}, ISSN={["0036-8075"]}, DOI={10.1126/science.1069580}, abstractNote={Polymer nanocomposites continue to receive tremendous attention for application in areas such as microelectronics, organic batteries, optics, and catalysis. We have discovered that physical dispersion of nonporous, nanoscale, fumed silica particles in glassy amorphous poly(4-methyl-2-pentyne) simultaneously and surprisingly enhances both membrane permeability and selectivity for large organic molecules over small permanent gases. These highly unusual property enhancements, in contrast to results obtained in conventional filled polymer systems, reflect fumed silica–induced disruption of polymer chain packing and an accompanying subtle increase in the size of free volume elements through which molecular transport occurs, as discerned by positron annihilation lifetime spectroscopy. Such nanoscale hybridization represents an innovative means to tune the separation properties of glassy polymeric media through systematic manipulation of molecular packing.}, number={5567}, journal={SCIENCE}, author={Merkel, TC and Freeman, BD and Spontak, RJ and He, Z and Pinnau, I and Meakin, P and Hill, AJ}, year={2002}, month={Apr}, pages={519–522} }
 @article{thongruang_balik_spontak_2002, title={Volume-exclusion effects in polyethylene blends filled with carbon black, graphite, or carbon fiber}, volume={40}, ISSN={["0887-6266"]}, DOI={10.1002/polb.10157}, abstractNote={Conductive polymer composites possessing a low percolation-threshold concentration as a result of double percolation of a conductive filler and its host phase in an immiscible polymer blend afford a desirable alternative to conventional composites. In this work, blends of high-density polyethylene (HDPE) and ultrahigh molecular weight polyethylene (UHMWPE) were used to produce ternary composites containing either carbon black (CB), graphite (G), or carbon fiber (CF). Blend composition had a synergistic effect on electrical conductivity, with pronounced conductivity maxima observed at about 70–80 wt % UHMWPE in the CB and G composites. A much broader maximum occurred at about 25 wt % UHMWPE in composites prepared with CF. Optical and electron microscopies were used to ascertain the extent to which the polymers, and hence filler particles, are segregated. Differential scanning calorimetry of the composites confirmed that the constituent polymers are indistinguishable in terms of their thermal signatures and virtually unaffected by the presence of any of the fillers examined here. Dynamic mechanical analysis revealed that CF imparts the greatest stiffness and thermal stability to the composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1013–1023, 2002}, number={10}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Thongruang, W and Balik, CM and Spontak, RJ}, year={2002}, month={May}, pages={1013–1025} }
 @article{smith_ade_smith_koch_spontak_2001, title={Anomalous phase inversion in polymer blends prepared by cryogenic mechanical alloying}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma001151p}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTAnomalous Phase Inversion in Polymer Blends Prepared by Cryogenic Mechanical AlloyingArchie P. Smith, Harald Ade, Steven D. Smith, Carl C. Koch, and Richard J. SpontakView Author Information Departments of Materials Science and Engineering, Physics, and Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695; and Corporate Research Division, The Procter and Gamble Company, Cincinnati, Ohio 45239 Cite this: Macromolecules 2001, 34, 6, 1536–1538Publication Date (Web):February 16, 2001Publication History Received5 July 2000Published online16 February 2001Published inissue 1 March 2001https://doi.org/10.1021/ma001151pCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views242Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (288 KB) Get e-AlertsSUBJECTS:Organic compounds,Polymer morphology,Polymers,Viscosity,X-ray absorption near edge spectroscopy Get e-Alerts}, number={6}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Smith, SD and Koch, CC and Spontak, RJ}, year={2001}, month={Mar}, pages={1536–1538} }
 @article{smith_ade_koch_spontak_2001, title={Cryogenic mechanical alloying as an alternative strategy for the recycling of tires}, volume={42}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(00)00804-1}, abstractNote={Abstract Cryogenic mechanical alloying (CMA) is investigated as a viable strategy by which to produce highly dispersed blends composed of thermoplastics and tire, thereby providing a potentially new route by which to recycle discarded tires. Morphological characterization of these blends by near-edge X-ray absorption fine structure (NEXAFS) microscopy demonstrates that, upon CMA, ground tire is highly dispersed within poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET) matrices at sub-micron size scales. Incorpo-ration of polyisoprene (PI) homopolymer into the blends to improve dispersion efficacy is also examined. Neither PI nor the tire is found to interact chemically with PMMA or PET under the milling conditions employed here.}, number={9}, journal={POLYMER}, author={Smith, AP and Ade, H and Koch, CC and Spontak, RJ}, year={2001}, month={Apr}, pages={4453–4457} }
 @article{mercurio_khan_spontak_2001, title={Dynamic rheological behavior of DBS-induced poly(propylene glycol) physical gels}, volume={40}, ISSN={["1435-1528"]}, DOI={10.1007/s003970000119}, number={1}, journal={RHEOLOGICA ACTA}, author={Mercurio, DJ and Khan, SA and Spontak, RJ}, year={2001}, month={Jan}, pages={30–38} }
 @article{arnold_nagai_freeman_spontak_betts_desimone_pinnau_2001, title={Gas permeation properties of poly(1,1 '-dihydroperfluorooctyl acrylate), poly(1,1 '-dihydroperfluorooetyl methacrylate), and poly(styrene)-b-poly(1,1 '-dihydroperfluorooctyl acrylate) block copolymers}, volume={34}, ISSN={["0024-9297"]}, DOI={10.1021/ma010355i}, abstractNote={The permeabilities of rubbery poly(1,1‘-dihydroperfluorooctyl acrylate) (PFOA), glassy poly(1,1‘-dihydroperfluorooctyl methacrylate) (PFOMA), and poly(styrene)-b-poly(1,1‘-dihydroperfluorooctyl acr...}, number={16}, journal={MACROMOLECULES}, author={Arnold, ME and Nagai, K and Freeman, BD and Spontak, RJ and Betts, DE and DeSimone, JM and Pinnau, I}, year={2001}, month={Jul}, pages={5611–5619} }
 @article{spontak_wilder_smith_2001, title={Improved network development in bidisperse AB/ABA block copolymer gels}, volume={17}, ISSN={["0743-7463"]}, DOI={10.1021/la0015819}, abstractNote={Blending a B-selective solvent and an ordered ABA triblock copolymer can, at sufficiently high solvent concentrations, produce a physical gel composed of a network of B midblocks stabilized by A-rich micelles. We demonstrate here that addition of short AB diblock copolymer molecules to such a gel at constant copolymer composition can enhance the solid-like character of the gel, as indicated by an increase in the magnitude of the dynamic elastic modulus. Similarly, addition of AB molecules to a nongelled ABA/solvent system can induce gelation. In light of recent theoretical predictions and related experimental evidence, these results are consistent with a scenario in which tail-induced volume exclusion (due to the presence of AB molecules) within the micellar coronas improves network development through an increase in the population of bridged B midblocks.}, number={8}, journal={LANGMUIR}, author={Spontak, RJ and Wilder, EA and Smith, SD}, year={2001}, month={Apr}, pages={2294–2297} }
 @article{jinnai_kajihara_watashiba_nishikawa_spontak_2001, title={Interfacial and topological measurements of bicontinuous polymer morphologies - art. no. 010803}, volume={6401}, number={1}, journal={Physica. E, Low-dimensional Systems & Nanostructures}, author={Jinnai, H. and Kajihara, T. and Watashiba, H. and Nishikawa, Y. and Spontak, R. J.}, year={2001}, pages={0803-} }
 @article{kane_norman_white_matsen_satkowski_smith_spontak_2001, title={Molecular, nanostructural and mechanical characteristics of lamellar triblock copolymer blends: Effects of molecular weight and constraint}, volume={22}, ISSN={["1521-3927"]}, DOI={10.1002/1521-3927(20010301)22:5<281::AID-MARC281>3.0.CO;2-G}, abstractNote={While theoretical and experimental efforts have thoroughly addressed microphase-ordered AB diblock copolymer blends with a parent homopolymer (hA or hB) or a second block copolymer, surprisingly few studies have considered comparable ABA triblock copolymers in the presence of hB or an AB diblock copolymer. In this study, we elucidate the roles of additive molecular weight and constraint by examining three matched series of miscible ABA/hB and ABA/AB blends. Self-consistent field theory is employed to analyze molecular characteristics, e. g., segmental distributions, microdomain periods and midblock bridging fractions, as functions of blend composition. Predictions are compared to morphological characteristics discerned by transmission electron microscopy and small-angle X-ray scattering. The corresponding mechanical properties of these blends are measured by dynamic mechanical analysis. The results of this comprehensive work reveal that addition of hB swells the B-lamellae of the ABA copolymer and has a generally deleterious effect on both the dynamic elastic modulus and midblock bridging fraction. In contrast, addition of a lamellar or cylindrical AB copolymer to the same ABA copolymer can promote an increase or decrease in lamellar period and bridging fraction, depending on relative block sizes.}, number={5}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Kane, L and Norman, DA and White, SA and Matsen, MW and Satkowski, MM and Smith, SD and Spontak, RJ}, year={2001}, month={Mar}, pages={281–296} }
 @article{mercurio_spontak_2001, title={Morphological characteristics of 1,3 : 2,4-dibenzylidene sorbitol/poly(propylene glycol) organogels}, volume={105}, ISSN={["1520-5207"]}, DOI={10.1021/jp002247o}, abstractNote={The organic gelator 1,3:2,4-dibenzylidene sorbitol (DBS) self-organizes to form a 3-D network stabilized by hydrogen bonds at relatively low concentrations in a variety of nonpolar organic solvents and polymers. The resultant network consists of nanofibrils and is responsible for the physical gelation of the matrix component. In this work, the morphological characteristics of organogels composed of DBS and poly(propylene glycol) (PPG) are investigated as functions of DBS concentration, PPG molecular weight, and temperature through the use of polarized light microscopy, transmission electron microscopy, X-ray diffractometry, and spectrophotometry. Polarized light microscopy reveals thermally reversible features that become increasingly more pronounced with increasing DBS concentration. Electron microscopy verifies that these features arise due to the presence of a DBS nanofibrillar network, with nanofibrils measuring ca. 10 nm in diameter. Comparison of X-ray diffraction patterns of pure DBS crystals and DBS networks from which PPG is removed by supercritical fluid extraction reveals that the DBS nanofibrils are crystalline, differing slightly from the structure of pure DBS. Spectrophotometry is used to probe the temperature-dependent development of the molecular network in DBS/PPG organogels.}, number={11}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Mercurio, DJ and Spontak, RJ}, year={2001}, month={Mar}, pages={2091–2098} }
 @article{smith_spontak_ade_2001, title={On the similarity of macromolecular responses to high-energy processes: mechanical milling vs. irradiation}, volume={72}, ISSN={["0141-3910"]}, DOI={10.1016/S0141-3910(01)00055-6}, abstractNote={Recent efforts to blend and compatibilize intrinsically immiscible polymers in the solid state by high-energy methods have shown that macromolecules may undergo scission, crosslinking or amorphization, depending on the chemical nature of the repeat unit, the processing temperature and the initial degree of polymer crystallinity. Identical process-induced molecular and structural modifications have been previously observed in polymers exposed to large doses of electron and γ radiation, suggesting that the responses of polymers to high-energy processes may be mechanistically similar. In this work, we explore a variety of similarities between mechanically-milled and irradiated polymers in terms of molecular characteristics, process temperature and polymer crystallinity, and we demonstrate that these similarities provide predictive guidance for the selection of polymers to be subjected to solid-state processing.}, number={3}, journal={POLYMER DEGRADATION AND STABILITY}, author={Smith, AP and Spontak, RJ and Ade, H}, year={2001}, pages={519–524} }
 @article{figueiredo_geppert_brandsch_bar_thomann_spontak_gronski_samlenski_muller-buschbaum_2001, title={Ordering of cylindrical microdomains in thin films of hybrid isotropic/liquid crystalline triblock copolymers}, volume={34}, ISSN={["0024-9297"]}, DOI={10.1021/ma0011441}, abstractNote={We have investigated the roles of liquid crystallinity (LC) and substrate interactions on the ordering of isotropic cylindrical microdomains in thin films of two hybrid isotropic/LC triblock copolymers. Each copolymer consists of polystyrene (PS) end blocks and a side-chain LC midblock that exhibits either a nematic or smectic mesophase up to temperatures beyond the glass transition temperature (Tg) of PS. In thin films measuring on the same order as the lattice period, the orientation of the cylinders relative to the substrate is sensitive to the interactions of the mesogens at internal microdomain boundaries and external interfaces. Upon annealing such copolymer films at temperatures below the LC → isotropic transition but above the PS Tg on a neutral NaCl substrate, the PS cylinders within the nematic matrix adopt a long-range parallel orientation, whereas those within the smectic matrix lie perpendicular to the substrate and exhibit liquidlike order. After long annealing times, the cylinders residing near the film surface within the smectic matrix reorganize from perpendicular to parallel orientation due to surface tension at the film/air interface. On a polished Si substrate that promotes homeotropic mesogen anchoring, the perpendicular cylindrical orientation within the smectic mesophase remains stable.}, number={2}, journal={MACROMOLECULES}, author={Figueiredo, P and Geppert, S and Brandsch, R and Bar, G and Thomann, R and Spontak, RJ and Gronski, W and Samlenski, R and Muller-Buschbaum, P}, year={2001}, month={Jan}, pages={171–180} }
 @article{spontak_smith_2001, title={Perfectly-alternating linear (AB)(n) multiblock copolymers: Effect of molecular design on morphology and properties}, volume={39}, ISSN={["0887-6266"]}, DOI={10.1002/polb.1070}, abstractNote={Perfectly-alternating linear (AB)n multiblock copolymers consist of n AB block pairs covalently linked in an alternating sequence. Although these copolymers can microphase-order in the same fashion as their lower-order (n = 1) diblock analogs, the 2(n − 1) biconformational midblocks comprising each copolymer molecule have a considerable impact on microstructural characteristics and bulk properties. We have applied transmission electron microscopy, differential scanning calorimetry (DSC), and extensional rheometry to examine and compare the morphologies and properties of two series of compositionally symmetric (lamellar) poly(styrene-b-isoprene)n (SI)n (1 ≤ n ≤ 4) multiblock copolymers. In one series, chain length was held constant allowing block mass (Mb) to decrease with increasing n. In the second copolymer series, Mb remained relatively invariant. Increasing n in these two series generally promoted reductions in both the lamellar period and upper (styrenic) glass-transition temperature, but noticeable increases in tensile modulus and yield strength. These observed trends are more pronounced in the copolymer series with constant chain length due to the coupled relationship between n and Mb. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 947–955, 2001}, number={9}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Spontak, RJ and Smith, SD}, year={2001}, month={May}, pages={947–955} }
 @article{sidorov_volkov_davankov_tsyurupa_valetsky_bronstein_karlinsey_zwanziger_matveeva_sulman_et al._2001, title={Platinum-containing hyper-cross-linked polystyrene as a modifier-free selective catalyst for L-sorbose oxidation}, volume={123}, ISSN={["0002-7863"]}, DOI={10.1021/ja0107834}, abstractNote={Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by H2 yields stable Pt nanoparticles with a mean diameter of 1.3 nm in THF and 1.4 nm in ML. The highest selectivity (98% at 100% conversion) measured during the catalytic oxidation of L-sorbose in water is obtained with the HPS-Pt-THF complex prior to H2 reduction. During an induction period of about 100 min, L-sorbose conversion is negligible while catalytic species develop in situ. The structure of the catalyst isolated after the induction period is analyzed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electron micrographs reveal a broad distribution of Pt nanoparticles, 71% of which measure less than or equal to 2.0 nm in diameter. These nanoparticles are most likely responsible for the high catalytic activity and selectivity observed. The formation of nanoparticles measuring up to 5.9 nm in diameter is attributed to the facilitated intercavity transport and aggregation of smaller nanoparticles in swollen HPS. The catalytic properties of these novel Pt nanoparticles are highly robust, remaining stable even after 15 repeated uses.}, number={43}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Sidorov, SN and Volkov, IV and Davankov, VA and Tsyurupa, MP and Valetsky, PM and Bronstein, LM and Karlinsey, R and Zwanziger, JW and Matveeva, VG and Sulman, EM and et al.}, year={2001}, month={Oct}, pages={10502–10510} }
 @article{smith_ade_koch_smith_spontak_2000, title={Addition of a block copolymer to polymer blends produced by cryogenic mechanical alloying}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma9915475}, abstractNote={Cryogenic mechanical alloying is used to incorporate a poly(methyl methacrylate-b-isoprene) (MI) diblock copolymer into blends of poly(methyl methacrylate) (PMMA) and polyisoprene (PI). Mechanical milling of the copolymer promotes a reduction in the molar mass of the M block, as discerned from glass transition temperature measurements performed by thermal calorimetry, and induces chemical cross-linking of the I block, as determined from sol−gel analysis. These effects become more pronounced with increasing milling time. Morphological characterization of PMMA-rich PI/MI/PMMA blends by X-ray and electron microscopies reveals that the characteristic size scale of the minority phase decreases with increasing MI content, as well as milling time. The nanostructural features observed in such blends are retained at relatively high MI concentrations during subsequent melt-pressing. Impact testing demonstrates that the blends become tougher upon addition of the MI copolymer, even at relatively low copolymer concentrations. Blend toughness likewise increases with increasing milling time up to a point, beyond which phase inversion occurs within the ternary blends (the PI becomes continuous) and impact strength sharply decreases.}, number={4}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Koch, CC and Smith, SD and Spontak, RJ}, year={2000}, month={Feb}, pages={1163–1172} }
 @article{smith_ade_balik_koch_smith_spontak_2000, title={Cryogenic mechanical alloying of poly(methyl methacrylate) with polyisoprene and poly(ethylene-alt-propylene)}, volume={33}, ISSN={["1520-5835"]}, DOI={10.1021/ma991453v}, abstractNote={Mechanical alloying is performed at cryogenic temperatures to incorporate polyisoprene (PI) or its hydrogenated analogue poly(ethylene-alt-propylene) (PEP) into poly(methyl methacrylate) (PMMA) as an example of high-energy solid-state blending. Morphological characterization of the blends by X-ray and electron microscopies confirms that the degree of dispersion of the constituent polymers improves with increasing milling time. Such dispersion in the PEP/PMMA blends is, however, ultimately compromised by phase coarsening when the materials are postprocessed above the PMMA glass transition temperature in the melt. Milling-induced PI cross-linking serves to suppress phase coarsening in PI/PMMA blends, which remain relatively well-dispersed even after postprocessing. These blends are generally less fracture-resistant than the as-received PMMA due mainly to the accompanying reduction in PMMA molecular weight. Their optical transparency is observed to decrease dramatically with increasing PEP or PI concentration until they appear opaque. An overall improvement in blend properties by mechanical alloying is, however, anticipated upon judicious selection of more degradation-resistant polymers.}, number={7}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Balik, CM and Koch, CC and Smith, SD and Spontak, RJ}, year={2000}, month={Apr}, pages={2595–2604} }
 @article{jinnai_nishikawa_spontak_smith_agard_hashimoto_2000, title={Direct measurement of interfacial curvature distributions in a bicontinuous block copolymer morphology}, volume={84}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.84.518}, abstractNote={Self-consistent field theory predicts that the complex phase behavior of block copolymers does not originate solely from the interface seeking constant mean curvature as once thought, but instead reflects competing minimization of interfacial tension and packing frustration. To test this prediction, we directly measure interfacial curvature distributions from a 3D image reconstruction of the bicontinuous gyroid morphology. Results obtained here reveal that the gyroid interface is not constant mean curvature and confirm the importance of packing frustration in the stabilization of such complex nanostructures.}, number={3}, journal={PHYSICAL REVIEW LETTERS}, author={Jinnai, H and Nishikawa, Y and Spontak, RJ and Smith, SD and Agard, DA and Hashimoto, T}, year={2000}, month={Jan}, pages={518–521} }
 @article{shay_english_spontak_balik_khan_2000, title={Dispersion polymerization of polystyrene latex stabilized with novel grafted poly(ethylene glycol) macromers in 1-propanol/water}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma992152o}, abstractNote={A novel hydrophilic macromer adapted for chemical grafting has been synthesized. It consists of methyl-end-capped poly(ethylene glycol) functionalized with a urethane terminus. Dispersion polymerization of styrene in an alcohol/water medium in the presence of the macromer allows chemical grafting of the macromer to the surfaces of the developing polystyrene (PS) latex particles. Scanning and transmission electron microscopies confirm the formation of spherical, submicron polystyrene particles. Transmission electron microscopy of films prepared from the latex particles also permits direct visualization of the stabilizing macromer layer grafted on the PS particle surfaces. Data acquired from proton nuclear magnetic resonance reveal a direct correlation between the concentration of macromer in the reaction mixture and the amount grafted to the latex particles. Rheological techniques are employed to (i) discern the stabilization efficacy of the macromer and (ii) identify correlations between latex and flow ch...}, number={18}, journal={MACROMOLECULES}, author={Shay, JS and English, RJ and Spontak, RJ and Balik, CM and Khan, SA}, year={2000}, month={Sep}, pages={6664–6671} }
 @inbook{leonard_spontak_russell_2000, title={Environmental atomic force microscopy: Probing diblock polymer thin films and self-assembling molecules at various temperatures and pressures}, volume={165}, ISBN={0750306858}, number={2000}, booktitle={Microbeam Analysis 2000: proceedings of the Second Conference of the International Union of Microbeam Analysis Societies held in Kailua-Kona, Hawaii, 9-14 July 2000}, publisher={Bristol: Institute of Physics Publishing}, author={Leonard, D. N. and Spontak, R. J. and Russell, P. E.}, editor={Williams, D. B. and Shimizu, R.Editors}, year={2000}, pages={389–390} }
 @article{smith_shay_spontak_balik_ade_smith_koch_2000, title={High-energy mechanical milling of poly(methyl methacrylate), polyisoprene and poly(ethylene-alt-propylene)}, volume={41}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(99)00830-7}, abstractNote={High-energy mechanical milling has been performed on poly(methyl methacrylate) (PMMA) at ambient and cryogenic temperatures, as well as on polyisoprene (PI) and poly(ethylene-alt-propylene) (PEP) at cryogenic conditions only. Milling conducted at ambient temperature has a substantially greater impact on the molecular characteristics of PMMA than milling at cryogenic temperatures. An increase in the milling time is accompanied by substantial reductions in PMMA molecular weight and, hence, glass transition temperature and impact strength under both sets of experimental conditions. An unexpected trend identified here is that the PMMA molecular weight distribution initially broadens and subsequently narrows with increasing milling time. Solid-state mechanical milling promotes comparable decreases in molecular weight and glass transition temperature in PEP (at a slower rate relative to PMMA), but induces chemical crosslinking in PI, as confirmed by FTIR spectroscopy. Charlesby–Pinner analysis yields not only the degree of PI crosslinking, but also the relative crosslinking and scission rates of PI, during cryogenic milling.}, number={16}, journal={POLYMER}, author={Smith, AP and Shay, JS and Spontak, RJ and Balik, CM and Ade, H and Smith, SD and Koch, CC}, year={2000}, month={Jul}, pages={6271–6283} }
 @misc{bronstein_chernyshov_valetsky_wilder_spontak_2000, title={Metal nanoparticles grown in the nanostructured matrix of poly(octadecylsiloxane)}, volume={16}, ISSN={["0743-7463"]}, DOI={10.1021/la0009341}, abstractNote={Metal nanoparticles grown within the nanostructured matrix of the amphiphilic polymer poly(octadecylsiloxane) (PODS) are investigated here by transmission electron microscopy. Due to its silanol groups and alkyl chain, PODS forms a bilayered nanostructure containing an intercalated layer of water within an aqueous environment. Replacement of water molecules with metal ions within the siloxy bilayers, followed by reduction, results in the formation of metal nanoparticles. The increase in electron density upon nanoparticle formation permits direct visualization of these bilayers, as well as the individual nanoparticles residing within them. These nanoparticles measure about 1−2 nm in diameter and possess a relatively narrow size distribution due presumably to volume availability within the ordered bilayers of PODS.}, number={22}, journal={LANGMUIR}, author={Bronstein, LM and Chernyshov, DM and Valetsky, PM and Wilder, EA and Spontak, RJ}, year={2000}, month={Oct}, pages={8221–8225} }
 @article{spontak_roberge_vratsanos_starner_2000, title={Model acrylate-terminated urethane blends in toughened epoxies: a morphology and stress relaxation study}, volume={41}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(99)00870-8}, abstractNote={Improved toughness of heat-cured epoxies is readily achieved through chemical incorporation of a flexible moiety that phase-separates from the epoxy matrix during thermal cure. Many commercial flexibilizers are inherently polydisperse, which yields dispersions composed of flexibilizer chains of variable length. In this work, we examine the effect of flexibilizer polydispersity on the morphology and stress relaxation behavior of a commercial epoxy. This is achieved by systematically varying the composition of binary and ternary flexibilizer blends of monodisperse acrylate-terminated urethanes differing in molecular weight. Field-emission scanning electron micrographs of fracture surfaces permit quantification of dispersion sizes as a function of blend composition. Tensile stress relaxation data from three-point bend tests performed under isothermal conditions are analyzed in terms of a biexponential model to discern fast and slow characteristic relaxation times.}, number={16}, journal={POLYMER}, author={Spontak, RJ and Roberge, RL and Vratsanos, MS and Starner, WE}, year={2000}, month={Jul}, pages={6341–6349} }
 @article{erlat_wang_spontak_tropsha_mar_montgomery_vogler_2000, title={Morphology and gas barrier properties of thin SiOx coatings on polycarbonate: Correlations with plasma-enhanced chemical vapor deposition conditions}, volume={15}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2000.0103}, number={3}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Erlat, AG and Wang, BC and Spontak, RJ and Tropsha, Y and Mar, KD and Montgomery, DB and Vogler, EA}, year={2000}, month={Mar}, pages={704–717} }
 @inproceedings{koch_smith_bai_spontak_balik_2000, title={Nonequilibrium processing of polymeric materials by mechanical attrition}, volume={343/346}, number={pts.1&2}, booktitle={International Symposium on Metastable, Mechanically Alloyed and Nanocrystalline Materials (1999: Dresden, Germany)}, publisher={Utikon-Zurich, Switz.; Enfield, NH: Trans Tech Publications}, author={Koch, C. C. and Smith, A. P. and Bai, C. and Spontak, R. J. and Balik, C. M.}, editor={J. Eckert, H. Schlorb and Schultz, L.Editors}, year={2000}, pages={49–561} }
 @article{spontak_vratsanos_2000, title={Stress relaxation activation in rubber-modified polymer systems exhibiting controlled miscibility through blending}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma991851y}, number={6}, journal={MACROMOLECULES}, author={Spontak, RJ and Vratsanos, MS}, year={2000}, month={Mar}, pages={2290–2292} }
 @article{bai_spontak_koch_saw_balik_2000, title={Structural changes in poly(ethylene terephthalate) induced by mechanical milling}, volume={41}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(00)00048-3}, abstractNote={Poly(ethylene terephthalate) (PET) has been subjected to high-energy ball milling (mechanical milling, MM) at three different temperatures. The resulting milled powder is characterized by molecular weight measurements, differential scanning calorimetry and wide-angle X-ray scattering. Regardless of the initial degree of crystallinity or milling temperature employed, MM apparently yields an “oriented amorphous” PET morphology in which the PET chains are locally aligned but rotationally disordered. This conclusion is based on the persistence of the (100) peak in otherwise amorphous x-ray patterns from milled PET. Thermograms of milled PET exhibit a small, broad crystallization exotherm and a large melting endotherm. The unusually small crystallization enthalpy is attributed to the local orientation of PET molecules present in the oriented amorphous morphology. Only minor rotations and translations of oriented PET molecules are needed to put the chains into register and, hence, the crystalline state. Evidence is also presented to suggest that extended-chain crystals of PET are produced upon crystallization of mechanically milled PET.}, number={19}, journal={POLYMER}, author={Bai, C and Spontak, RJ and Koch, CC and Saw, CK and Balik, CM}, year={2000}, month={Jun}, pages={7147–7157} }
 @article{smith_spontak_koch_smith_ade_2000, title={Temperature-induced morphological evolution in polymer blends produced by cryogenic mechanical alloying}, volume={274}, DOI={10.1002/(sici)1439-2054(20000101)274:1<1::aid-mame1>3.3.co;2-r}, number={1}, journal={Macromolecular Materials and Engineering}, author={Smith, A. P. and Spontak, Richard and Koch, C. C. and Smith, S. D. and Ade, H.}, year={2000}, pages={1–12} }
 @article{spontak_patel_2000, title={Thermoplastic elastomers: fundamentals and applications}, volume={5}, number={5-6}, journal={Current Opinion in Colloid & Interface Science}, author={Spontak, R. J. and Patel, N. P.}, year={2000}, pages={334–341} }
 @article{kane_spontak_1999, title={A-methylstyrene}, journal={Polymer data handbook}, publisher={New York: Oxford University Press}, author={Kane, L. and Spontak, R.J.}, year={1999}, pages={680–687} }
 @misc{spontak_alexandridis_1999, title={Advances in self-ordering macromolecules and nanostructure design}, volume={4}, ISSN={["1359-0294"]}, DOI={10.1016/S1359-0294(99)00023-0}, abstractNote={Nanostructured macromolecules, such as block copolymers, elucidate the fundamental principles governing self-organization in soft condensed matter. Significant experimental and theoretical advances regarding complex morphology development in bulk copolymers and their homopolymer blends have recently been achieved. New equilibrium block copolymer morphologies have been reported for copolymers in the super-strong segregation regime, and the pathways by which bicontinuous morphologies in copolymers and copolymer blends form have been identified. Emerging research directions target chemically tailored copolymer systems as designer templates for uniform ceramic nanostructures and field-responsive devices with switchable molecular orientation.}, number={2}, journal={CURRENT OPINION IN COLLOID & INTERFACE SCIENCE}, author={Spontak, RJ and Alexandridis, P}, year={1999}, month={Apr}, pages={140–146} }
 @article{sidorov_bronstein_davankov_tsyurupa_solodovnikov_valetsky_wilder_spontak_1999, title={Cobalt nanoparticle formation in the pores of hyper-cross-linked polystyrene: Control of nanoparticle growth and morphology}, volume={11}, ISSN={["0897-4756"]}, DOI={10.1021/cm990274p}, abstractNote={Impregnation of hyper-cross-linked polystyrene (HPS) by either Co2(CO)8 in 2-propanol or the [Co(DMF)6]2+[Co(CO)4]-2 complex in dimethylformamide (DMF), followed by thermolysis at 200 °C, results in the formation of discrete Co nanoparticles. The concentration and characteristics of such nanoparticles were investigated by X-ray fluorescence (XRF) spectroscopy, ferromagnetic resonance (FMR) spectroscopy, and transmission electron microscopy (TEM). The FMR data here confirm the formation of spherical nanoparticles. At relatively low concentrations of Co, the magnitude of the FMR line width reveals that the mean Co nanoparticle diameter is about 2 nm, which agrees closely with the mean particle diameter discerned by TEM. An increase in Co content higher than 8 wt % is accompanied by an increase in mean particle diameter due to an increase in the population of large Co nanoparticles up to 15 nm across. Regulated nanoparticle growth over a wide range of Co concentrations is attributed to nanoscale HPS cavities, which serve to physically restrict the size of growing particles.}, number={11}, journal={CHEMISTRY OF MATERIALS}, author={Sidorov, SN and Bronstein, LM and Davankov, VA and Tsyurupa, MP and Solodovnikov, SP and Valetsky, PM and Wilder, EA and Spontak, RJ}, year={1999}, month={Nov}, pages={3210–3215} }
 @article{schneider_geppert_spontak_gronski_finkelmann_1999, title={Effect of composition on the morphology and electro-optical properties of physically crosslinked liquid crystals}, volume={559}, ISBN={["1-55899-466-1"]}, ISSN={["0272-9172"]}, DOI={10.1557/proc-559-177}, journal={LIQUID CRYSTAL MATERIALS AND DEVICES}, publisher={Warrendale, PA: Materials Research Society}, author={Schneider, A and Geppert, S and Spontak, RJ and Gronski, W and Finkelmann, H}, year={1999}, pages={177–182} }
 @article{busick_spontak_balik_1999, title={Effects of graphite content on the morphology and barrier properties of poly(vinylidene fluoride) composites}, volume={40}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(98)00826-X}, abstractNote={Abstract We have performed a series of morphology and CO2-probe diffusion analyses to ascertain the existence and composition dependence of voids in graphite/poly(vinylidene fluoride) composites both above and below the graphite percolation threshold, as determined from electrical conductivity measurements. Sorption data indicate that, with increasing graphite loading: (i) the diffusivity of CO2 in the composite material decreases; and (ii) the volume fraction of voids in the material increases. Differential scanning calorimetry reveals that polymer crystals nucleate heterogeneously on graphite particles and that samples containing graphite have higher degrees of crystallinity than the neat polymer. Crystallinity effects appear to dominate barrier properties at low graphite loadings, while porosity effects dominate at high graphite loadings. Our results strongly suggest that, although voids in these composites are probably associated with relatively poor adhesion along graphite/polymer interfaces, the voids are also discrete (i.e. they do not form a continuous network, even if the graphite particles do).}, number={22}, journal={POLYMER}, author={Busick, DN and Spontak, RJ and Balik, CM}, year={1999}, month={Oct}, pages={6023–6029} }
 @article{wang_tropsha_montgomery_vogler_spontak_1999, title={Enhanced barrier performance of SiOx-modified polymer substrates: some morphological considerations}, volume={18}, ISSN={["0261-8028"]}, DOI={10.1023/A:1006687324051}, number={4}, journal={JOURNAL OF MATERIALS SCIENCE LETTERS}, author={Wang, BC and Tropsha, Y and Montgomery, DB and Vogler, EA and Spontak, RJ}, year={1999}, month={Feb}, pages={311–315} }
 @article{walker_raghavan_royer_smith_wignall_melnichenko_khan_spontak_1999, title={Enhanced miscibility of low-molecular-weight polystyrene polyisoprene blends in supercritical CO2}, volume={103}, ISSN={["1089-5647"]}, DOI={10.1021/jp990551f}, abstractNote={While ongoing efforts continue to explore the high-pressure phase equilibria of polymer blends, few studies have attempted to address the impact of a supercritical (sc) fluid on such equilibria. In this work, we report on the phase behavior of an upper critical solution temperature (UCST) polymer blend in the presence of supercritical carbon dioxide (scCO2), a nonselective plasticizing agent. Blends composed of low-molecular-weight polystyrene and polyisoprene have been examined as a function of temperature in scCO2 by visual inspection, small-angle neutron scattering, and spectrophotometry. In the presence of scCO2, the cloud point temperature is depressed by as much as 28 °C, depending on both blend composition and CO2 pressure. Complementary studies performed with nitrogen decouple the plasticization efficacy of CO2 from free-volume compression due to hydrostatic pressure. Existence of a pressure yielding a maximum in CO2-induced cloud point depression is established. These results provide evidence for enhanced polymer miscibility as a result of the plasticizing effectiveness and tunable solubility of scCO2.}, number={26}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Walker, TA and Raghavan, SR and Royer, JR and Smith, SD and Wignall, GD and Melnichenko, Y and Khan, SA and Spontak, RJ}, year={1999}, month={Jul}, pages={5472–5476} }
 @article{driscoll_gulati_spontak_hall_1999, title={Grafted polymer tail loop mixtures differing in chain length}, volume={40}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(98)00804-0}, abstractNote={Abstract Studies examining the structure of monolayers formed by polymer chains grafted to a surface typically focus on chains attached at one end (tails). Bond fluctuation simulations are performed here to probe monolayers composed of equimolar mixtures of tails and double-grafted loops in which the looped chain length (Nloop) is varied at constant surface density and tail length (Ntail). Loops force the tails to adopt an extended trajectory normal to the surface, resulting in monolayer stratification. As Nloop increases, the height of the tail sublayer increases to a maximum, and then decreases to converge with the loop sublayer as Nloop→2Ntail. These results are compared to predictions from a self-consistent field theory for bidisperse mixtures of grafted tails.}, number={18}, journal={POLYMER}, author={Driscoll, DC and Gulati, HS and Spontak, RJ and Hall, CK}, year={1999}, month={Aug}, pages={5207–5211} }
 @article{smith_spontak_ade_smith_koch_1999, title={High-energy cryogenic blending and compatibilizing of immiscible polymers}, volume={11}, ISSN={["1521-4095"]}, DOI={10.1002/(SICI)1521-4095(199910)11:15<1277::AID-ADMA1277>3.0.CO;2-9}, abstractNote={Low-temperature mechanical alloying of immiscible polymers is investigated as a viable solid-state alternative to blending using melt or solution processes. The Figure is a schematic diagram of the alloying—or high-energy ball-milling—process, indicating that reactive chain coupling may occur in the event of free-radical generation due to chain scission.}, number={15}, journal={ADVANCED MATERIALS}, author={Smith, AP and Spontak, RJ and Ade, H and Smith, SD and Koch, CC}, year={1999}, month={Oct}, pages={1277-+} }
 @article{king_white_smith_spontak_1999, title={Mesogel networks via selective midblock swelling of lamellar triblock copolymers}, volume={15}, ISSN={["0743-7463"]}, DOI={10.1021/la9816407}, abstractNote={A lamellar ABA triblock copolymer brought to equilibrium in the presence of a B-compatible solvent generally swells or transforms into an A-dispersed (cylindrical or micellar) morphology, depending on solvent content. If the A blocks of the copolymer are glassy, they serve as physical cross-links and stabilize a gel network in which A microdomains are linked through a combination of connected B bridges and entangled B loops. An alternate route by which to introduce solvent into a triblock copolymer, as well as retain the local molecular anisotropy (and bridge population) of the initial lamellar morphology, is to selectively swell the B block and, at sufficiently high solvent concentrations, produce a mesogel. In this work, we describe the formation of mesogels from two chemically related triblock copolymers and employ dynamic mechanical analysis and transmission electron microscopy to examine the features of the resultant nonequilibrium materials.}, number={23}, journal={LANGMUIR}, author={King, MR and White, SA and Smith, SD and Spontak, RJ}, year={1999}, month={Nov}, pages={7886–7889} }
 @misc{spontak_roberts_prevysh_khan_1999, title={Method of reducing the viscosity of a black liquor using thiocyanate salt}, volume={5,900,112}, number={1999 May 4}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Spontak, R. J. and Roberts, J. E. and Prevysh, V. A. and Khan, S. A.}, year={1999} }
 @article{jackson_wilder_white_bukovnik_spontak_1999, title={Modification of a thermoplastic elastomer gel through the addition of an endblock-selective homopolymer}, volume={37}, ISSN={["1099-0488"]}, DOI={10.1002/(SICI)1099-0488(19990801)37:15<1863::AID-POLB10>3.0.CO;2-X}, abstractNote={Addition of a midblock-selective oil to an ABA triblock copolymer with a rubbery B-midblock and thermoplastic A-endblocks yields a thermoplastic elastomer gel (TPEG) if the oil constitutes the majority blend constituent and a physically crosslinked network, responsible for solid-like mechanical properties, is retained. These blends typically exhibit a micellar morphology in which the micellar cores are composed of the oil-incompatible A-endblocks. Since the micelles serve as crosslink sites, the properties of TPEGs depend on (i) the intrinsic characteristics of the solid-state endblocks, and (ii) the degree to which the micelles interact through bridged and looped midblocks. In this work, a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and an aliphatic oil are used to prepare TPEGs into which poly(2,6-dimethylphenylene oxide) (PPO), a styrene-compatible homopolymer, is added. The morphologies and bulk properties of these ternary systems are examined by electron microscopy, viscometry, and dynamic rheology. A slight increase in the PPO content in these TPEGs promotes increases in micelle size, confirming that the PPO primarily resides within the micelles, and disordering temperature, signified by an abrupt change in rheological properties. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1863–1872, 1999}, number={15}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Jackson, NR and Wilder, EA and White, SA and Bukovnik, R and Spontak, RJ}, year={1999}, month={Aug}, pages={1863–1872} }
 @article{king_white_smith_spontak_1999, title={Morphology and property development in block copolymer mesogels}, volume={15}, number={1999}, journal={Langmuir}, author={King, M. R. and White, S. A. and Smith, S. D. and Spontak, R.J.}, year={1999}, pages={7886-} }
 @article{laurer_khan_spontak_satkowski_grothaus_smith_lin_1999, title={Morphology and rheology of SIS and SEPS triblock copolymers in the presence of a midblock-selective solvent}, volume={15}, ISSN={["0743-7463"]}, DOI={10.1021/la981441n}, abstractNote={While numerous fundamental studies have sought to elucidate the effect of a parent homopolymer on the morphological characteristics and mechanical properties of microphase-ordered block copolymer blends, few comparable efforts have extended such studies to concentrated copolymer solutions in the presence of a low-molar-mass block-selective solvent. In this work, we investigate the microstructures that form in blends of a poly(styrene-block-isoprene-block-styrene) (SIS) triblock copolymer with a midblock-selective aliphatic mineral oil. To discern the influence of midblock/oil compatibility on blend morphology and properties, identical blends with a poly[styrene-block-(ethylene-alt-propylene)-block-styrene] (SEPS) copolymer, the hydrogenated variant of the SIS copolymer, have likewise been examined. The saturated midblock of the SEPS copolymer is responsible for the observed shifts in morphology stability limits and higher dynamic elastic shear moduli relative to the SIS analogue. These results reveal that the morphologies and properties of such triblock copolymer/oil blends are sensitive to the chemical/statistical nature of the copolymer midblock and may be judiciously tailored to satisfy application-specific requirements.}, number={23}, journal={LANGMUIR}, author={Laurer, JH and Khan, SA and Spontak, RJ and Satkowski, MM and Grothaus, JT and Smith, SD and Lin, JS}, year={1999}, month={Nov}, pages={7947–7955} }
 @article{laurer_spontak_1999, title={P-chlorostyrene}, journal={Polymer data handbook}, publisher={New York: Oxford University Press}, author={Laurer, J. H. and Spontak, R. J.}, year={1999}, pages={380–386} }
 @article{smith_spontak_1999, title={P-methylstyrene}, journal={Polymer data handbook}, publisher={New York: Oxford University Press}, author={Smith, A. P. and Spontak, R. J.}, year={1999}, pages={688–695} }
 @article{erlat_spontak_clarke_robinson_haaland_tropsha_harvey_vogler_1999, title={SiOx gas barrier coatings on polymer substrates: Morphology and gas transport considerations}, volume={103}, ISSN={["1089-5647"]}, DOI={10.1021/jp990737e}, abstractNote={Plasma-enhanced chemical vapor deposition (PECVD) of SiOx thin coatings on polymer surfaces yields tough hybrid materials with the gas barrier properties and transparency of glass. Combination of these properties makes these materials ideally suited for food packaging and biomedical device applications. In this study, we employ a Non-Parametric Response Surface Methods optimization to identify the Magnetron-PECVD conditions responsible for superlative SiOx barrier coatings on poly(ethylene terephthalate) (PET). Oxygen and water vapor permeances of optimized PET/SiOx composites produced by hexamethyldisiloxane and trimethylsilane have been measured as functions of temperature and are found to exhibit Arrhenius behavior. The thermal activation energy for water vapor permeation, unlike that for oxygen permeation, depends on barrier performance and increases by as much as 20 kJ/mol with an increase in barrier efficacy. Examination of these materials by phase-imaging atomic force microscopy and energy-filtered...}, number={29}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Erlat, AG and Spontak, RJ and Clarke, RP and Robinson, TC and Haaland, PD and Tropsha, Y and Harvey, NG and Vogler, EA}, year={1999}, month={Jul}, pages={6047–6055} }
 @misc{alexandridis_spontak_1999, title={Solvent-regulated ordering in block copolymers}, volume={4}, ISSN={["1879-0399"]}, DOI={10.1016/S1359-0294(99)00022-9}, abstractNote={Studies of the structural polymorphism exhibited by block copolymers in the presence of selective solvents are relatively recent, but very promising in terms of fundamental understanding and practical applications. Highlighting recent advances, this review progresses from `dry' ordered copolymers to solvated ordered (gel-like) copolymers and lastly to solvated disordered (but locally organized) copolymers. Organic- and aqueous-solvent-based systems are concurrently examined to cross-fertilize polymer and colloid science.}, number={2}, journal={CURRENT OPINION IN COLLOID & INTERFACE SCIENCE}, author={Alexandridis, P and Spontak, RJ}, year={1999}, month={Apr}, pages={130–139} }
 @article{hong_stolken_zielinski_smith_duda_spontak_1998, title={Anomalous sorption in a poly(styrene-b-isoprene) diblock copolymer near the order-disorder transition}, volume={31}, ISSN={["0024-9297"]}, DOI={10.1021/ma971127k}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTAnomalous Sorption in a Poly(styrene-b-isoprene) Diblock Copolymer near the Order−Disorder TransitionSeong-Uk Hong, Sylvia Stölken, John M. Zielinski, Steven D. Smith, J. Larry Duda, and Richard J. SpontakView Author Information Departments of Materials Science & Engineering and Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Physikalische Chemie, Johannes Gutenberg Universität, 55099 Mainz, Germany, Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239, and Departments of Chemical Engineering and Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695 Cite this: Macromolecules 1998, 31, 3, 937–940Publication Date (Web):January 14, 1998Publication History Received28 July 1997Revised13 November 1997Published online14 January 1998Published inissue 1 February 1998https://doi.org/10.1021/ma971127kCopyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views81Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (54 KB) Get e-AlertsSUBJECTS:Aromatic compounds,Copolymers,Hydrocarbons,Solvents,Sorption Get e-Alerts}, number={3}, journal={MACROMOLECULES}, author={Hong, SU and Stolken, S and Zielinski, JM and Smith, SD and Duda, JL and Spontak, RJ}, year={1998}, month={Feb}, pages={937–940} }
 @article{laurer_hajduk_dreckotter_smith_spontak_1998, title={Bicontinuous morphologies in homologous multiblock copolymers and their homopolymer blends}, volume={31}, ISSN={["0024-9297"]}, DOI={10.1021/ma9807872}, number={21}, journal={MACROMOLECULES}, author={Laurer, JH and Hajduk, DK and Dreckotter, S and Smith, SD and Spontak, RJ}, year={1998}, month={Oct}, pages={7546–7549} }
 @article{laurer_smith_samseth_mortensen_spontak_1998, title={Interfacial modification as a route to novel bilayered morphologies in binary block copolymer/homopolymer blends}, volume={31}, ISSN={["1520-5835"]}, DOI={10.1021/ma980200j}, abstractNote={Addition of a relatively low-molecular-weight parent homopolymer to a lamellar AB diblock copolymer constitutes a reliable means by which to induce, in controllable fashion, transitions to other morphologies. In this study, we examine the effect of interfacial modification on such transitions in “extended” A(A/B)B copolymer/homopolymer blends in which (i) the A/B midblock fraction (relative to the copolymer molecular weight) is varied from 0.0 to 0.4 in 0.1 increments and (ii) the overall concentration of A ranges from 0.50 to 0.95. As this A/B fraction is increased at constant blend composition, the extent of homopolymer-induced lamellar swelling becomes measurably less pronounced, indicating that the A/B midblock serves to delocalize repulsion along the interphase separating adjacent lamellae. At higher homopolymer concentrations, an increase in the A/B fraction results in the formation of either unilamellar vesicles or a randomly connected bilayered membrane, rather than micelles. These membranes become unstable and transform to micelles at high copolymer dilution. The results presented here are discussed in terms of the complex morphologies observed in, and predicted for, low-molar-mass (co)surfactant systems.}, number={15}, journal={MACROMOLECULES}, author={Laurer, JH and Smith, SD and Samseth, J and Mortensen, K and Spontak, RJ}, year={1998}, month={Jul}, pages={4975–4985} }
 @article{kabra_gehrke_spontak_1998, title={Microporous, responsive hydroxypropyl cellulose gels. 1. Synthesis and microstructure}, volume={31}, ISSN={["1520-5835"]}, DOI={10.1021/ma970418q}, abstractNote={An effective technique for the synthesis of microporous gels is developed along with correlations between synthesis conditions and microstructure. Such gels have substantially different properties than their nonporous analogues. Microporous hydroxypropyl cellulose (HPC) gels were prepared by heating aqueous HPC solutions above their lower critical solution temperatures (LCST's) while cross-linking the polymer with divinyl sulfone. The effective porosity of the gel increased from 23 to 76% by decreasing HPC concentration from 22.6 to 9 wt %, as anticipated from the system phase diagram. The pore size range decreased from 0.5−9.0 to 0.05−0.2 μm by increasing reaction time before phase separation from 1.5 to 25 min, demonstrating that cross-linking in the homogeneous state limits the extent of phase separation possible. Gel morphology changed from open-celled to closed-celled by decreasing reaction time in the phase-separated state, which limits cross-linking in the polymer-rich phase.}, number={7}, journal={MACROMOLECULES}, author={Kabra, BG and Gehrke, SH and Spontak, RJ}, year={1998}, month={Apr}, pages={2166–2173} }
 @article{yashin_spontak_1998, title={Miscibilization of reactive polymers during early-stage spinodal decomposition}, volume={44}, ISSN={["1547-5905"]}, DOI={10.1002/aic.690440218}, abstractNote={Reactive compatibilization constitutes an important method by which to control the size scale of phase separation in immiscible polymer blends. If a polymer pair exhibits a miscibility window at experimentally accessible temperatures, then reactive chain coupling can also be used to enhance the miscibility of the blend during spinodal decomposition in the biphasic region. We consider here the simultaneous phase separation and chemical reaction of A and B homopolymer blends in which end-functionalized A chains react with a variety of functionalized B chains to form either AB diblock, ABA triblock, or n-armed B-g-A graft copolymers. Analytical expressions for the structure factors and Onsager kinetic coefficients are developed for each of these copolymer architectures in the kinetically controlled mean-field limit of early-stage spinodal decomposition. Multifunctional conversion-architecture-phase stability (CAPS) diagrams are introduced to facilitate comparison of the effect of copolymer architecture on reaction-driven blend miscibilization.}, number={2}, journal={AICHE JOURNAL}, author={Yashin, VV and Spontak, RJ}, year={1998}, month={Feb}, pages={416–426} }
 @article{driscoll_gulati_spontak_hall_1998, title={Mixtures of polymer tails and loops grafted to an impenetrable interface}, volume={39}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(97)10122-7}, abstractNote={Property modification of an inorganic surface can be readily achieved through the use of macromolecules chemically grafted to the surface at specific functional sites along the chain. While numerous efforts have addressed the properties of linear chains grafted at one end (tails), relatively few have extended such studies to include double-tethered chains (loops). In this work, we consider loop/tail mixtures in which both chain species possess an identical number of repeat units. Bond-fluctuation simulations have been performed to ascertain the effects of composition, chain length and surface density on the segmental density distribution and layer height of each constituent species and of the mixture. These results compare favourably with self-consistent field predictions for bidisperse mixtures of grafted tails differing in length by a factor of two.}, number={25}, journal={POLYMER}, author={Driscoll, DC and Gulati, HS and Spontak, RJ and Hall, CK}, year={1998}, month={Dec}, pages={6339–6346} }
 @article{hong_laurer_zielinski_samseth_smith_duda_spontak_1998, title={Morphological and isothermal diffusive probe analyses of low-molecular-weight diblock copolymers}, volume={31}, ISSN={["0024-9297"]}, DOI={10.1021/ma971516e}, abstractNote={While numerous scattering and rheological studies have investigated the disordering mechanism of low-molecular-weight poly(styrene-b-isoprene) (SI) diblock copolymers, relatively few efforts have addressed the real-space morphologies and transport properties of such copolymers at conditions near the order−disorder transition (ODT). In this work, the morphological features of seven compositionally symmetric (50/50 w/w S/I) copolymers ranging in molecular weight from 5000 to 20000, as well as several of their blends, are examined by transmission electron microscopy and small-angle neutron scattering. These results are used to interpret toluene gravimetric sorption data collected at various temperatures. At temperatures above the styrenic glass transition temperature, microphase-ordered copolymer melts are found to exhibit Fickian diffusion. In the case of a copolymer with an experimentally accessible ODT, anomalous sorption (as evidenced by equilibrium overshoot in gravimetric mass-uptake curves) is observed at temperatures near, but below, the ODT. Within the disordered state, Fickian diffusion is regained, indicating that the onset of anomalous diffusion is related to a solvent-induced ODT under isothermal conditions.}, number={7}, journal={MACROMOLECULES}, author={Hong, SU and Laurer, JH and Zielinski, JM and Samseth, J and Smith, SD and Duda, JL and Spontak, RJ}, year={1998}, month={Apr}, pages={2174–2184} }
 @article{laurer_mulling_khan_spontak_bukovnik_1998, title={Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior}, volume={36}, DOI={10.1002/(sici)1099-0488(19980930)36:13<2379::aid-polb13>3.3.co;2-7}, abstractNote={Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron micrographs reveal that gels with 70 to 90 wt % oil exhibit styrenic micelles measuring ca. 24 nm in diameter. Variation in composition or cooling rate does not have any perceivable effect on micelle size or shape, whereas the rate at which the gels are cooled influences the extent of microstructural order and the time to rupture (tR) at constant strain. Dynamic rheological testing confirms the presence of a physically crosslinked network at TPEG compositions ranging from 70 to 90 wt % oil, independent of cooling rate. Results presented here suggest that the dynamic elastic shear modulus (G′) scales as tαR where α varies from 0.41 to 0.59, depending on cooling rate. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2379–2391, 1998}, number={13}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Laurer, J. H. and Mulling, J. F. and Khan, Saad and Spontak, Richard and Bukovnik, R.}, year={1998}, pages={2379–2391} }
 @article{laurer_mulling_khan_spontak_lin_bukovnik_1998, title={Thermoplastic elastomer gels. II. Effects of composition and temperature on morphology and gel rheology}, volume={36}, DOI={10.1002/(sici)1099-0488(199810)36:14<2513::aid-polb5>3.3.co;2-6}, number={14}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Laurer, J. H. and Mulling, J. F. and Khan, Saad and Spontak, Richard and Lin, J. S. and Bukovnik, R.}, year={1998}, pages={2513–2523} }
 @article{norman_kane_white_smith_spontak_1998, title={Triblock copolymer/homopolymer blends: Conformational changes, microstructural transition and macrophase separation}, volume={17}, ISSN={["0261-8028"]}, DOI={10.1023/A:1006565418979}, number={7}, journal={JOURNAL OF MATERIALS SCIENCE LETTERS}, author={Norman, DA and Kane, L and White, SA and Smith, SD and Spontak, RJ}, year={1998}, month={Apr}, pages={545–549} }
 @article{smith_bai_ade_spontak_balik_koch_1998, title={X-ray microscopy characterization of a thermoplastic / liquid crystalline polymer blend produced by mechanical alloying}, volume={19}, DOI={10.1002/marc.1998.030191104}, abstractNote={Incorporation of liquid crystalline polymers (LCPs) into commodity polymers remains a challenge in the design of high-performance, low-cost polymeric blends. Blends of a thermoplastic polymer and a nematic LCP are produced here by mechanical alloying. Functionality sensitive X-ray microscopy reveals LCP dispersions as small as 100 nm in diameter. Intimate mixing remains upon subsequent melt processing, indicating that mechanical alloying is suited for applications such as recycling.}, number={1998}, journal={Macromolecular Rapid Communications}, author={Smith, Andy and Bai, C. and Ade, H. and Spontak, Richard and Balik, C. M. and Koch, C. C.}, year={1998}, pages={557} }
 @article{laurer_ashraf_smith_spontak_1997, title={Complex phase behavior of a disordered ''random'' diblock copolymer in the presence of a parent homopolymer}, volume={13}, ISSN={["0743-7463"]}, DOI={10.1021/la960807y}, abstractNote={Previous efforts addressing binary blends of a block copolymer and a parent homopolymer have principally employed ordered copolymers in either the intermediate- or strong-segregation regimes. In this work, blends composed of a disordered (75/25)-b-(50/50) poly[(styrene-r-isoprene)‘-b-(styrene-r-isoprene)‘‘] (S/I)‘-b-(S/I)‘‘ random diblock copolymer (RBC) and homopolystyrene (hS) have been investigated. Blend morphologies, characterized by transmission electron microscopy, are correlated with hS concentration and molecular weight, as well as with changes in the hS Tg, as measured by thermal calorimetry. At low hS fractions (up to 20 wt % hS), the S/I block sequences in the RBC induce competition between attractive and repulsive interactions with hS molecules, resulting in the formation of thin hS channel structures in a continuous RBC matrix. An increase in hS concentration or molecular weight serves to broaden the channels until the morphology resembles macrophase-separated hS domains containing micelle-like RBC dispersions. In blends with relatively high hS fractions (greater than 80 wt % hS), repulsive interactions between RBC and hS molecules are responsible for the formation of macroscopic RBC domains in a continuous hS matrix. These blend morphologies demonstrate that localized interactions between homopolymer molecules and each block of a copolymer exist, and can be probed, in the disordered state.}, number={8}, journal={LANGMUIR}, author={Laurer, JH and Ashraf, A and Smith, SD and Spontak, RJ}, year={1997}, month={Apr}, pages={2250–2258} }
 @article{kane_satkowski_smith_spontak_1997, title={Compositionally symmetric diblock copolymer blends of moderate polydispersity}, volume={35}, DOI={10.1002/(sici)1099-0488(19971130)35:16<2653::aid-polb8>3.3.co;2-d}, number={16}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Kane, L. and Satkowski, M. M. and Smith, S. D. and Spontak, Richard}, year={1997}, pages={2653–2658} }
 @inproceedings{gulati_jones_driscoll_spontak_hall_1997, title={Conformational and dynamic properties of polymer loops and their mixtures at an impenetrable interface}, volume={463}, DOI={10.1557/proc-463-109}, booktitle={Statistical mechanics in physics and biology: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A, 1997  (Materials Research Society symposia proceedings)}, author={Gulati, H. S. and Jones, R. L. and Driscoll, D. C. and Spontak, Richard and Hall, C. K.}, editor={D. Wirtz and Halsey, T. C.Editors}, year={1997}, pages={109–114} }
 @inproceedings{kane_norman_white_spontak_1997, title={Effect of additive constraint on the morphological and mechanical properties of triblock copolymer blends}, volume={461}, DOI={10.1557/proc-461-75}, booktitle={Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings)}, publisher={Warrendale, PA: Materials Research Society}, author={Kane, L. and Norman, D. A. and White, S. A. and Spontak, Richard}, editor={R. M. Briber, C. C. Han and Peiffer, D. G.Editors}, year={1997}, pages={75–80} }
 @article{balik_spontak_weitzel_1997, title={Evolution of VIMS at North Carolina State University}, volume={19}, number={1-2}, journal={Journal of Materials Education}, author={Balik, C. M. and Spontak, Robert J. and Weitzel, J.}, year={1997}, pages={59} }
 @article{laurer_fung_sedat_smith_samseth_mortensen_agard_spontak_1997, title={From micelles to randomly connected, bilayered membranes in dilute block copolymer blends}, volume={13}, ISSN={["0743-7463"]}, DOI={10.1021/la9608876}, abstractNote={As macromolecular surfactants, diblock copolymers order into a variety of morphologies in the presence of a parent homopolymer. Here, we probe the effects of chemical incompatibility and interfacial rigidity on the morphology of copolymer/homopolymer blends at constant blend composition. Five copolymers, each possessing a random-sequence midblock that is varied from 0 to 40 wt % of the copolymer molecular weight, have been synthesized for this purpose. While copolymer micelles are representative of dilute (homopolymer-rich) blends, complex bilayered morphologies, including vesicles and the anomalous isotropic “sponge” phase, are produced upon increasing the midblock fraction. Small-angle neutron scattering provides a quantitative assessment of characteristic microstructural dimensions, while transmission electron microtomography yields the first three-dimensional images of the randomly connected, bilayered membrane comprising the sponge phase.}, number={8}, journal={LANGMUIR}, author={Laurer, JH and Fung, JC and Sedat, JW and Smith, SD and Samseth, J and Mortensen, K and Agard, DA and Spontak, RJ}, year={1997}, month={Apr}, pages={2177–2180} }
 @article{toy_freeman_spontak_morisato_pinnau_1997, title={Gas permeability and phase morphology of poly(1-(trimethylsilyl)-1-propyne)/poly(1-phenyl-1-propyne) blends}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma970091t}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTGas Permeability and Phase Morphology of Poly(1-(trimethylsilyl)-1-propyne)/Poly(1-phenyl-1-propyne) BlendsLora G. Toy, Benny D. Freeman, Richard J. Spontak, Atsushi Morisato, and Ingo PinnauView Author Information Departments of Chemical Engineering and Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 Membrane Technology and Research, Inc., 1360 Willow Road, Suite 103, Menlo Park, California 94025 Cite this: Macromolecules 1997, 30, 16, 4766–4769Publication Date (Web):August 11, 1997Publication History Received22 January 1997Revised19 May 1997Published online11 August 1997Published inissue 1 August 1997https://doi.org/10.1021/ma970091tCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views362Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (146 KB) Get e-AlertsSUBJECTS:Colloids,Interface engineering,Permeability,Selectivity,Transmission electron microscopy Get e-Alerts}, number={16}, journal={MACROMOLECULES}, author={Toy, LG and Freeman, BD and Spontak, RJ and Morisato, A and Pinnau, I}, year={1997}, month={Aug}, pages={4766–4769} }
 @article{laurer_ashraf_smith_samseth_spontak_1997, title={Macromolecular self-assembly in dilute sequence-controlled block copolymer/homopolymer blends}, volume={4}, ISSN={["0968-5677"]}, DOI={10.1016/S0968-5677(96)00048-X}, abstractNote={Conventional block copolymers consist of two long contiguous monomer sequences (‘blocks’) that can, in the same fashion as low-molar-mass surfactants, self-assemble into various microstructural elements (e.g., micelles at low copolymer concentrations) to minimize repulsive contacts in the presence of a parent homopolymer. In this work, we explore the existence of segment-specific interactions, as well as the possibility of tailoring these blend morphologies (and producing altogether new ones), with novel sequence-controlled block copolymers. These copolymers are comprised of at least one block that is a random segment composed of both constituent monomer species. Transmission electron microscopy is employed here to examine the bilayered membranes and channel structures that form in two different series of such copolymers in dilute copolymer/homopolymer blends.}, number={1-2}, journal={SUPRAMOLECULAR SCIENCE}, author={Laurer, JH and Ashraf, A and Smith, SD and Samseth, J and Spontak, RJ}, year={1997}, pages={121–126} }
 @inproceedings{balik_bai_koch_spontak_saw_1997, title={Mechanical alloying of PET and PET/Vectra blends}, volume={461}, booktitle={Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings)}, publisher={Warrendale, PA: Materials Research Society}, author={Balik, C. M. and Bai, C. and Koch, C. C. and Spontak, R. J. and Saw, C. K.}, editor={R. M. Briber, C. C. Han and Peiffer, D. G.Editors}, year={1997}, pages={39} }
 @misc{spontak_roberts_prevysh_khan_1997, title={Method of reducing the viscosity of a black liquor}, volume={5,635,027}, number={1997 June 3}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Spontak, R. J. and Roberts, J. E. and Prevysh, V. A. and Khan, S. A.}, year={1997} }
 @article{laurer_hajduk_fung_sedat_smith_gruner_agard_spontak_1997, title={Microstructural analysis of a cubic bicontinuous morphology in a neat SIS triblock copolymer}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma970449l}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTMicrostructural Analysis of a Cubic Bicontinuous Morphology in a Neat SIS Triblock CopolymerJonathan H. Laurer, Damian A. Hajduk, Jennifer C. Fung, John W. Sedat, Steven D. Smith, Sol M. Gruner, David A. Agard, and Richard J. SpontakView Author Information Department of Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695, Department of Physics, Princeton University, Princeton, New Jersey 08544, Graduate Group in Biophysics, University of California, San Francisco, California 94143, Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143, Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239, and Howard Hughes Medical Institute, University of California, San Francisco, California 94143 Cite this: Macromolecules 1997, 30, 13, 3938–3941Publication Date (Web):June 30, 1997Publication History Received1 April 1997Published online30 June 1997Published inissue 1 June 1997https://doi.org/10.1021/ma970449lCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views631Altmetric-Citations88LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (202 KB) Get e-AlertsSUBJECTS:Copolymers,Morphology,Order,Scattering,X-ray scattering Get e-Alerts}, number={13}, journal={MACROMOLECULES}, author={Laurer, JH and Hajduk, DA and Fung, JC and Sedat, JW and Smith, SD and Gruner, SM and Agard, DA and Spontak, RJ}, year={1997}, month={Jun}, pages={3938–3941} }
 @article{fung_kane_smith_sedat_agard_spontak_1997, title={Phase behavior of complex diblock copolymer blends: A transmission electron microscopy study}, volume={239-}, ISBN={["0-87849-756-0"]}, ISSN={["0255-5476"]}, DOI={10.4028/www.scientific.net/msf.239-241.179}, journal={PROCEEDINGS OF THE 13TH INTERNATIONAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS - ICDIM 96}, publisher={Utikon-Zurich, Switz.; Enfield, N.H.: Trans Tech Publications}, author={Fung, JC and Kane, L and Smith, SD and Sedat, JW and Agard, DA and Spontak, RJ}, year={1997}, pages={179–184} }
 @inproceedings{laurer_mulling_bukovnik_spontak_1997, title={Phase behavior of triblock copolymers upon incorporation of nonparent, midblock-associating additives}, volume={461}, DOI={10.1557/proc-461-69}, booktitle={Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings)}, publisher={Warrendale, PA: Materials Research Society}, author={Laurer, J. H. and Mulling, J. F. and Bukovnik, R. and Spontak, Richard}, editor={R. M. Briber, C. C. Han and Peiffer, D. G.Editors}, year={1997}, pages={69–74} }
 @article{wang_spontak_1997, title={Phase behaviour of aqueous hydroxypropylcellulose mesophase mixtures: Molecular weight considerations}, volume={22}, ISSN={["0267-8292"]}, DOI={10.1080/026782997209432}, abstractNote={As a self-organizing macromolecule, hydroxypropylcellulose serves as an excellent candidate for studies of complex polymer mixtures. In this work, we examine aqueous mixtures composed of two hydroxypropylcellulose grades, Klucel-F (HPC) and Klucel-H (HHPC), with molecular weights of 10 5 and 10 6 g mol - 1, respectively. Polarized light microscopy and deuterium nuclear magnetic resonance have been utilized to ascertain changes in the chiral nematic mesophase of HPC upon addition of 15 wt% HHPC. Results obtained here suggest that the HHPC either disrupts the molecular organization of the HPC mesophase, or induces immiscibility and partitions between HPC- and HHPC-rich phases.}, number={3}, journal={LIQUID CRYSTALS}, author={Wang, BC and Spontak, RJ}, year={1997}, month={Mar}, pages={359–365} }
 @article{prevysh_wang_khan_spontak_1997, title={Salting-in behavior of isotropic and anisotropic aqueous hydroxypropylcellulose solutions}, volume={275}, ISSN={["0303-402X"]}, DOI={10.1007/s003960050082}, number={3}, journal={COLLOID AND POLYMER SCIENCE}, author={Prevysh, VA and Wang, BC and Khan, SA and Spontak, RJ}, year={1997}, month={Mar}, pages={284–287} }
 @article{shepard_delsorbo_louth_walborn_norman_harvey_spontak_1997, title={Self-organization and polyolefin nucleation efficacy of 1,3:2,4-di-p-methylbenzylidene sorbitol}, volume={35}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(19971130)35:16<2617::AID-POLB5>3.0.CO;2-M}, abstractNote={Recent studies have demonstrated that addition of a small quantity of dibenzylidene sorbitol (DBS) to a molten polymer may result in a physical gel if conditions permit the DBS molecules to self-organize into a three-dimensional network composed of highly connected nanofibrils. If the polymer crystallizes, DBS may also serve as a nucleating agent, promoting the formation of spherulites, especially in commercially important polyolefins such as polypropylene. We examine the thermal and mechanical properties, as well as the morphological characteristics, of an isotactic polypropylene copolymer with 3 wt % ethylene upon addition of less than 1 wt % of 1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS). From dynamic rheological measurements, pronounced complex viscosity increases, attributed to MDBS nanofibril network formation, are observed at concentration-dependent temperatures above the melting point of the nucleated copolymer. Transmission electron micrographs of RuO4-stained sections confirm the existence of MDBS nanofibrils measuring on the order of 10 nm in diameter and, at higher concentrations, fibrillar bundles measuring up to about 200 nm across and several microns in length. The addition of MDBS at different concentrations is also found to promote increases in optical clarity, yield strength, tensile strength, and ultimate elongation of modified copolymer formulations. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2617–2628, 1997}, number={16}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Shepard, TA and Delsorbo, CR and Louth, RM and Walborn, JL and Norman, DA and Harvey, NG and Spontak, RJ}, year={1997}, month={Nov}, pages={2617–2628} }
 @article{prebola_spontak_1997, title={The introductory course in materials thermodynamics: Strategies toward improved instructional effectiveness}, volume={19}, number={1997}, journal={Journal of Materials Education}, author={Prebola, J. L. and Spontak, R. J.}, year={1997}, pages={47} }
 @article{smith_laurer_ade_smith_ashraf_spontak_1997, title={X-ray microscopy and NEXAFS spectroscopy of macrophase-separated random block copolymer/homopolymer blends}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma9612687}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTX-ray Microscopy and NEXAFS Spectroscopy of Macrophase-Separated Random Block Copolymer/Homopolymer BlendsArchie P. Smith, Jonathan H. Laurer, Harald W. Ade, Steven D. Smith, Arman Ashraf, and Richard J. SpontakView Author Information Departments of Materials Science & Engineering and Physics, North Carolina State University, Raleigh, North Carolina 27695, and Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239 Cite this: Macromolecules 1997, 30, 3, 663–666Publication Date (Web):February 10, 1997Publication History Received20 August 1996Revised13 November 1996Published online10 February 1997Published inissue 1 February 1997https://doi.org/10.1021/ma9612687Copyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views143Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (158 KB) Get e-AlertsSUBJECTS:Colloids,Copolymers,Energy,Transmission electron microscopy,X-rays Get e-Alerts}, number={3}, journal={MACROMOLECULES}, author={Smith, AP and Laurer, JH and Ade, HW and Smith, SD and Ashraf, A and Spontak, RJ}, year={1997}, month={Feb}, pages={663–666} }
 @article{roberts_spontak_jameel_khan_1996, title={A novel approach to black liquor viscosity reduction using salt additives}, volume={79}, number={8}, journal={TAPPI Journal}, author={Roberts, J.E. and Spontak, R.J. and Jameel, H. and Khan, S.A.}, year={1996}, pages={167–174} }
 @article{roberts_khan_spontak_1996, title={Controlled black liquor viscosity reduction through salting-in}, volume={42}, ISSN={["0001-1541"]}, DOI={10.1002/aic.690420821}, abstractNote={Black liquor viscosity increases exponentially with solids content and therefore causes processing problems for the paper industry by being a limiting factor in the Kraft pulp process. This study investigates a new approach for achieving viscosity reduction by salting-in black liquor through the addition of thiocyanate salts. These salts generally increase the solubility of the polymer constituents in black liquor, leading to a decrease in its viscosity. Several thiocyanate salts capable of reducing liquor viscosity by more than two orders of magnitude have been identified, with viscosity reduction greatest at high solids content. Salting-in of black liquor depends on the cation paired with the thiocyanate anion, as well as on solution pH and temperature. Comparative studies reveal the most effective viscosity-reducing agent of the series examined and that lignin plays an important role in the viscosity behavior of both unmodified and salted-in black liquor at high solids concentrations. These experimental findings are interpreted in terms of the underlying principles that describe salting-in and how it affects aqueous solution structure.}, number={8}, journal={AICHE JOURNAL}, author={Roberts, JE and Khan, SA and Spontak, RJ}, year={1996}, month={Aug}, pages={2319–2326} }
 @article{nunez_whitfield_mercurio_ilzhoefer_spontak_khan_1996, title={Effect of molecular architecture on DBS-induced block copolymer gels: A rheological study}, volume={106}, ISSN={["1022-1360"]}, DOI={10.1002/masy.19961060126}, abstractNote={Dibenzylidene sorbitol (DBS) is capable of gelling a variety of organic solvents and polymeric materials by forming a rigid, 3-D hydrogen-bonded network. In this work, two poly(siloxane)/poly(propylene oxide) segmented copolymers of equal composition and molecular weight, but different architectures (endblocked vs. pendant), as well as a pure poly(propylene oxide), have been gelled with DBS. We have investigated the dynamic rheological properties of these gels to ascertain the effect of copolymer architecture, PDMS comonomer and DBS concentration on network formation.}, journal={MACROMOLECULAR SYMPOSIA}, author={Nunez, CM and Whitfield, JK and Mercurio, DJ and Ilzhoefer, JR and Spontak, RJ and Khan, SA}, year={1996}, month={Apr}, pages={275–286} }
 @misc{ilzhoefer_broom_nepa_vogler_khan_spontak_1995, title={EVIDENCE OF HIERARCHICAL ORDER IN AN AMPHIPHILIC GRAFT TERPOLYMER GEL}, volume={99}, ISSN={["0022-3654"]}, DOI={10.1021/j100032a002}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence of Hierarchical Order in an Amphiphilic Graft Terpolymer GelJohn R. Ilzhoefer, Brian C. Broom, Stephen M. Nepa, Erwin A. Vogler, Saad A. Khan, and Richard J. SpontakCite this: J. Phys. Chem. 1995, 99, 32, 12069–12071Publication Date (Print):August 1, 1995Publication History Published online1 May 2002Published inissue 1 August 1995https://doi.org/10.1021/j100032a002RIGHTS & PERMISSIONSArticle Views114Altmetric-Citations22LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts}, number={32}, journal={JOURNAL OF PHYSICAL CHEMISTRY}, author={ILZHOEFER, JR and BROOM, BC and NEPA, SM and VOGLER, EA and KHAN, SA and SPONTAK, RJ}, year={1995}, month={Aug}, pages={12069–12071} }
 @article{prevysh_spontak_khan_1995, title={Tailored viscosity reduction in aqueous hydroxypropylcellulose solutions}, volume={394}, ISBN={["1-55899-297-9"]}, ISSN={["0272-9172"]}, DOI={10.1557/proc-394-137}, journal={POLYMERS IN MEDICINE AND PHARMACY}, author={Prevysh, VA and Spontak, RJ and Khan, SA}, year={1995}, pages={137–142} }