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Copolymer Membranes (copolymer + membrane)
Selected AbstractsOriginal Fuel-Cell Membranes from Crosslinked Terpolymers via a "Sol,gel" StrategyADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Ozlem Sel Abstract Hybrid organic/inorganic membranes that include a functionalized (-SO3H), interconnected silica network, a non-porogenic organic matrix, and a -SO3H-functionalized terpolymer are synthesized through a sol,gel-based strategy. The use of a novel crosslinkable poly(vinylidene fluoride- ter -perfluoro(4-methyl-3,6-dioxaoct-7-ene sulfonyl fluoride)- ter -vinyltriethoxysilane) (poly(VDF- ter -PFSVE- ter -VTEOS)) terpolymer allows a multiple tuning of the different interfaces to produce original hybrid membranes with improved properties. The synthesized terpolymer and the composite membranes are characterized, and the proton conductivity of a hybrid membrane in the absence of the terpolymer is promising, since 8,mS cm,1 is reached at room temperature, immersed in water, with an experimental ion-exchange-capacity (IECexp) value of 0.4,meq g,1. Furthermore, when the composite membranes contain the interfaced terpolymer, they exhibit both a higher proton conductivity (43,mS cm,1 at 65 °C under 100% relative humidity) and better stability than the standard hybrid membrane, arising from the occurrence of a better interface between the inorganic silica and the poly[(vinylidene fluoride)- co -hexafluoropropylene] (poly(VDF- co -HFP)) copolymer network. Accordingly, the hybrid SiO2 -SO3H/terpolymer/poly(VDF- co -HFP) copolymer membrane has potential use as an electrolyte in a polymer-electrolyte-membrane fuel cell operating at intermediate temperatures. [source] Synthesis and characterization of sulfonated-fluorinated, hydrophilic-hydrophobic multiblock copolymers for proton exchange membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2009Xiang Yu Abstract Hydrophilic/hydrophobic block copolymers as proton exchange membranes (PEMs) has become an emerging area of research in recent years. These copolymers were obtained through moderate temperature (, 100 °C) coupling reactions, which minimize the ether-ether interchanges between hydrophobic and hydrophilic telechelic oligomers via a nucleophilic aromatic substitution mechanism. The hydrophilic blocks were based on the nucleophilic step polymerization of 3,3,-disulfonated, 4,4,-dichlorodiphenyl sulfone with an excess 4,4,-biphenol to afford phenoxide endgroups. The hydrophobic (fluorinated) blocks were largely based on decafluoro biphenyl (excess) and various bisphenols. The copolymers were obtained in high molecular weights and were solvent cast into tough membranes, which had nanophase separated hydrophilic and hydrophobic regions. The performance and structure-property relationships of these materials were studied and compared to random copolymer systems. NMR results supported that the multiblock sequence had been achieved. They displayed superior proton conductivity, due to the ionic proton conducting channels formed through the self-assembly of the sulfonated blocks. The nano-phase separated morphologies of the copolymer membranes were studied and confirmed by atomic force microscopy. Through control of a variety of parameters, including ion exchange capacity and sequence lengths, performances as high, or even higher than those of the state-of-the-art PEM, Nafion, were achieved. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1038,1051, 2009 [source] Solid-supported amphiphilic triblock copolymer membranes grafted from gold surfaceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2009Ekaterina Rakhmatullina Abstract Gold-supported amphiphilic triblock copolymer brushes composed of two hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) blocks and a hydrophobic poly(n -butyl methacrylate) (PBMA) middle part were synthesized using a surface-initiated ATRP. Attenuated total reflectance Fourier transform infrared spectroscopy, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), ellipsometry, contact angle measurements, and atomic force microscopy were used for the characterization of PHEMA- co -PBMA- co -PHEMA brushes. The PM-IRRAS analysis revealed an increase of the chain tilt toward the gold surface during growth of the individual blocks. We suggest that the orientation of the amphiphilic polymer brushes is influenced by both the chain length and the interchain interactions. Additionally, a detachment of the polymer membranes from the solid support and subsequent gel permeation chromatography analyses allowed us to establish their compositions. We applied block-selective solvents (water and hexane) as well as a good solvent for the whole polymer chain (ethanol) to study the morphology and solvent responsive behavior of the amphiphilic brushes. The presented results could serve as a good starting point for the fabrication of functional solid-supported membranes for biosensing applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1,13, 2009 [source] Microphase-Separated Poly(vinylpyridine) Block Copolymer Prepared with a Novel Bifunctional InitiatorMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2009Masami Shoji Abstract A vinylpyridine block copolymer was prepared by stepwise controlled/living radical polymerization with a novel bifunctional initiator, 4-(2-bromopropanoyloxy)- N -(p -methylbenzyloxy)-2,2,6,6-tetramethylpiperidine. The initiator was synthesized in a facile manner using commercially available p -xylene and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-hydroxy TEMPO). Through stepwise atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and nitroxide-mediated radical polymerization (NMRP) of 4-vinylpyridine (4VP), the PMMA- b- P4VP copolymer was prepared with a wide range of the copolymer compositions. Microphase-separation was demonstrated in cross sectional TEM images of self-standing block copolymer membranes. [source] Synthesis and Properties of Novel Fluorinated Poly(phenylene- co -imide)sMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2007Wenmu Li Abstract A new class of high-performance materials, fluorinated poly(phenylene- co -imide)s, were prepared by Ni(0)-catalytic coupling of 2,5-dichlorobenzophenone with fluorinated dichlorophthalimide. The synthesized copolymers have high molecular weights (,=,5.74,×,104,17.3,×,104 g,·,mol,1), and a combination of desirable properties such as high solubility in common organic solvent, film-forming ability, and excellent mechanical properties. The glass transition temperature (Tgs) of the copolymers was readily tuned to be between 219 and 354,°C via systematic variation of the ratio of the two comonomers. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 66.7,266 MPa, 2.7,13.5%, and 3.13,4.09 GPa, respectively. The oxygen permeability coefficients () and permeability selectivity of oxygen to nitrogen () of these copolymer membranes were in the range of 0.78,3.01 barrer [1 barrer,=,10,10 cm3 (STP) cm/(cm2,·,s,·,cmHg)] and 5.09,6.25, respectively. Consequently, these materials have shown promise as engineering plastics and gas-separation membrane materials. [source] Accurate control of oxygen level in cells during culture on silicone rubber membranes with application to stem cell differentiationBIOTECHNOLOGY PROGRESS, Issue 3 2010Daryl E. Powers Abstract Oxygen level in mammalian cell culture is often controlled by placing culture vessels in humidified incubators with a defined gas phase partial pressure of oxygen (pO2gas). Because the cells are consuming oxygen supplied by diffusion, a difference between pO2gas and that experienced by the cells (pO2cell) arises, which is maximal when cells are cultured in vessels with little or no oxygen permeability. Here, we demonstrate theoretically that highly oxygen-permeable silicone rubber membranes can be used to control pO2cell during culture of cells in monolayers and aggregates much more accurately and can achieve more rapid transient response following a disturbance than on polystyrene and fluorinated ethylene-propylene copolymer membranes. Cell attachment on silicone rubber was achieved by physical adsorption of fibronectin or Matrigel. We use these membranes for the differentiation of mouse embryonic stem cells to cardiomyocytes and compare the results with culture on polystyrene or on silicone rubber on top of polystyrene. The fraction of cells that are cardiomyocyte-like increases with decreasing pO2 only when using oxygen-permeable silicone membrane-based dishs, which contract on silicone rubber but not polystyrene. The high permeability of silicone rubber results in pO2cell being equal to pO2gas at the tissue-membrane interface. This, together with geometric information from histological sections, facilitates development of a model from which the pO2 distribution within the resulting aggregates is computed. Silicone rubber membranes have significant advantages over polystyrene in controlling pO2cell, and these results suggest they are a valuable tool for investigating pO2 effects in many applications, such as stem cell differentiation. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | ||||||||||