@article{goli_gera_liu_rao_rojas_genzer_2013, title={Generation and Properties of Antibacterial Coatings Based on Electrostatic Attachment of Silver Nanoparticles to Protein-Coated Polypropylene Fibers}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am4011644}, abstractNote={We present a simple method for attaching silver nanoparticles to polypropylene (PP) fibers in a two-step process to impart antibacterial properties. Specifically, PP fibers are pretreated by the adsorption from an aqueous solution of heat-denatured lysozyme (LYS) followed by LYS cross-linking using glutaraldehyde and sodium borohydride. At neutral pH, the surface of the adsorbed LYS layer is enriched with numerous positive charges. Silver nanoparticles (AgNPs) capped with trisodium citrate are subsequently deposited onto the protein-coated PP. Nanoparticle binding is mediated by electrostatic interactions between the positively charged LYS layer and the negatively charged AgNPs. The density of AgNPs deposited on PP depends on the amount of protein adsorbed on the surface. UV-vis spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy are employed to follow all preparation steps and to characterize the resulting functional surfaces. The antibacterial activity of the modified surfaces is tested against gram negative bacteria Escherichia coli (E. coli). Overall, our results show that PP surfaces coated with AgNPs exhibit excellent antibacterial activity with 100% removal efficiency.}, number={11}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Goli, Kiran K. and Gera, Nimish and Liu, Xiaomeng and Rao, Balaji M. and Rojas, Orlando J. and Genzer, Jan}, year={2013}, month={Jun}, pages={5298–5306} }
 @article{liu_vesterinen_genzer_seppala_rojas_2011, title={Adsorption of PEO-PPO-PEO Triblock Copolymers with End-Capped Cationic Chains of Poly(2-dimethylaminoethyl methacrylate)}, volume={27}, ISSN={["0743-7463"]}, DOI={10.1021/la201596x}, abstractNote={We study the adsorption of a symmetric triblock copolymer of ethylene oxide, EO, and propylene oxide, PO, end-capped with quarternized poly(2-dimethylaminoethyl methacrylate), DMAEMA (DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24)). Light scattering and tensiometry are used to measure the relative size of the associated structures and surface excess at the air-liquid interface. The adsorbed amount, the amount of coupled water, and the viscoelasticity of the adsorbed polymer layer are measured on hydrophobic and hydrophilic surfaces (polypropylene, cellulose, and silica) by using quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR) at different ionic strengths and temperatures. The results of the experiments are compared with those obtained after adsorption of the uncharged precursor copolymer, without the cationic end-caps (EO(132)PO(50)EO(132)). DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) possesses higher affinity with the negatively charged silica and cellulose surfaces while the uncharged copolymer adsorbs to a larger extent on polypropylene surfaces. In this latter case, adsorption increases with increasing solution ionic strength and temperature. Adsorption of EO(132)PO(50)EO(132) on silica surfaces has little effect on the water contact angle (WCA), while adsorption of DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) increases the WCA of silica to 32°, indicating a large density of exposed PPO blocks upon adsorption. After adsorption of EO(132)PO(50)EO(132) and DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) on PP, the WCA is reduced by ≈14° and ≈28°, respectively, due to the exposed hydrophilic EO and highly water-soluble DMAEMA segments on the surfaces. The extent of surface coverage at saturation at the polypropylene/liquid interfaces (≈31 and 40 nm(2)/molecule obtained by QCM and SPR, respectively) is much lower, as expected, when compared with results obtained at the air/liquid interface, where a tighter packing is observed. The percentage of water coupled to the adsorbed cationic polymer decreases with solution ionic strength. Overall, these observations are ascribed to the effects of electrostatic screening, polymer hydrodynamic size, and solvency.}, number={16}, journal={LANGMUIR}, author={Liu, Xiaomeng and Vesterinen, Arja-Helena and Genzer, Jan and Seppala, Jukka V. and Rojas, Orlando J.}, year={2011}, month={Aug}, pages={9769–9780} }
 @article{zhang_cao_feng_xu_su_liu_lu_2011, title={Application of fourier transform attenuated total reflection infrared spectroscopy in analysis of pulp and paper industry}, volume={31}, number={3}, journal={Spectroscopy and Spectral Analysis}, author={Zhang, Y. and Cao, C. Y. and Feng, W. Y. and Xu, M. and Su, Z. H. and Liu, X. M. and Lu, W. J.}, year={2011}, pages={652–655} }
 @article{liu_goli_genzer_rojas_2011, title={Multilayers of Weak Polyelectrolytes of Low and High Molecular Mass Assembled on Polypropylene and Self-Assembled Hydrophobic Surfaces}, volume={27}, ISSN={["0743-7463"]}, DOI={10.1021/la200349p}, abstractNote={Hydrophobic self-assembled octadecyltrichlorosilane (ODTS), ultrathin films of polypropylene, and ODTS modified with cationic dioctadecyldimethylammonium bromide are employed as substrates for deposition of multilayers of poly(allylamine hydrochloride) and poly(acrylic acid) from aqueous solution. The assembly of highly dissipative polyelectrolyte multilayers (PEMs) is demonstrated by quartz crystal microgravimetry. The initial rate of adsorption is faster and the adsorbed amount larger on the cationic surface, while the detailed structure of the PEMs, as determined by atomic force microscopy imaging, is related primarily to the molecular weight of the adsorbing polymers. A more extensive PEM adsorption on the hydrophobic surfaces takes place with increasing ionic strength of the background electrolyte solution. The water contact angle depends on the type of polymer adsorbed as the outermost layer, indicating that, despite the expected interdiffusion for the different polymer chains, there is a net macromolecular segregation to the free surface. Surface modification with the high molecular weight PEMs produces a more marked reduction of the hydrophilicity of the substrate.}, number={8}, journal={LANGMUIR}, author={Liu, Xiaomeng and Goli, Kiran K. and Genzer, Jan and Rojas, Orlando J.}, year={2011}, month={Apr}, pages={4541–4550} }
 @article{liu_wu_turgman-cohen_genzer_theyson_rojas_2010, title={Adsorption of a Nonionic Symmetric Triblock Copolymer on Surfaces with Different Hydrophobicity}, volume={26}, ISSN={["0743-7463"]}, DOI={10.1021/la100156a}, abstractNote={This study investigates the adsorption of a symmetric triblock nonionic polymer comprising ethylene oxide (EO) and propylene oxide (PO) blocks (Pluronic P-105, EO(37)PO(56)EO(37)) on a range of substrates including hydrophobic, i.e., polypropylene (PP), poly(ethylene terephthalate) (PET), nylon, and graphite, and hydrophilic, i.e., cellulose and silica. The adsorption process and the structure of the hydrated adsorbed layers are followed by quartz crystal microgravimetry (QCM), surface plasmon resonance (SPR), and atomic force microscopy. The unhydrated surfaces are characterized by ellipsometry and contact angle techniques. The adsorption kinetics and the extent of adsorption are determined by monitoring the changes in resonance frequency and refractive index of sensors coated with ultrathin films of the various substrates. Langmuirian-type adsorption kinetics is observed in all cases studied. The amount of adsorbed Pluronic on hydrophobic polymer surfaces (PP, PET, and nylon) exceeds that on the hydrophilic cellulose. The hydrophobic (graphite) mineral surface adsorbs relatively low polymer mass, typical of a monolayer, while micellar structures are observed on the hydrophilic silica surface. The amount of water coupled to the adsorbed polymer layers is quantified by combining data from QCM, and SPR are found to increase with increasing polarity of the substrate. On the basis of contact angle data, the nonhydrated adsorbed structures produce modest increases in hydrophilicity of all the substrates investigated. Overall, insights are provided into the structure and stability of both hydrated and nonhydrated adsorbed triblock copolymer.}, number={12}, journal={LANGMUIR}, author={Liu, Xiaomeng and Wu, Dong and Turgman-Cohen, Salomon and Genzer, Jan and Theyson, Thomas W. and Rojas, Orlando J.}, year={2010}, month={Jun}, pages={9565–9574} }
 @article{liu_song_wu_genzer_theyson_rojas_2010, title={Surface and Friction Behavior of a Silicone Surfactant Adsorbed on Model Textiles Substrates}, volume={49}, ISSN={["0888-5885"]}, DOI={10.1021/ie1012213}, abstractNote={This study reports on interactions of an amphiphilic block copolymer of polyalkylene oxide-modified poly(dimethylsiloxane) with thin films of polypropylene (PP), polyethylene terephthalate (PET), and nylon, as well as with reference hydrophilic silica surfaces. The dynamics of adsorption, adsorbed mass, and viscoelasticity of the adsorbed layer are quantified by using a quartz crystal microbalance, while boundary layer lubrication behaviors are studied by using lateral force microscopy. Driven by hydrophobic interactions, the silicone surfactant adsorbs following a Langmuir isotherm and forms strongly adsorbed layers on the polymer surfaces with an areal mass directly related to the hydrophobicity of the substrate. The self-assembled silicone surfactant molecules improve significantly wettability and lower friction. The results reported herein will broaden our understanding of lubrication phenomena in textile and fiber processing applications.}, number={18}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Liu, Xiaomeng and Song, Junlong and Wu, Dong and Genzer, Jan and Theyson, Thomas and Rojas, Orlando J.}, year={2010}, month={Sep}, pages={8550–8557} }
 @article{song_liang_liu_krause_hinestroza_rojas_2009, title={Development and characterization of thin polymer films relevant to fiber processing}, volume={517}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2009.03.015}, abstractNote={Dilute solutions of cellulose, polypropylene, polyethylene, nylon and polyester were spun cast onto gold and silica wafers to generate thin films of these polymers, which are commonly used in the manufacture of synthetic fibers. The thin films were used as substrates in the quartz crystal microbalance and nano-indentation techniques to monitor adsorption and friction behaviors after treatment with a polymer solution (as a mimic of a textile finish). The spin coating conditions were optimized in terms of the resulting film morphology, thickness and surface energy. Atomic force microscopy, X-ray photoelectron spectrometry, ellipsometry and contact angle were used to probe the physical and surface properties of the resulting films. Overall, we developed thin films that are helpful to inquire, at the molecular level, phenomena relevant to fiber and textile processing including swelling, degradation, and adsorption of polymers and surfactants.}, number={15}, journal={THIN SOLID FILMS}, author={Song, Junlong and Liang, Jing and Liu, Xiaomeng and Krause, Wendy E. and Hinestroza, Juan P. and Rojas, Orlando J.}, year={2009}, month={Jun}, pages={4348–4354} }
 @article{zhang_pu_liu_wu_2008, title={Characterization of the alkali-tolerant thermostable enzyme from Saccharomonospora viridis and its application in pulp bleaching}, volume={42}, number={7-8}, journal={Cellulose Chemistry and Technology}, author={Zhang, Y. and Pu, J. W. and Liu, X. M. and Wu, Y. Y.}, year={2008}, pages={363–369} }