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Proton-exchange Membranes (proton-exchange + membrane)
Selected AbstractsCorrelation between Morphology, Water Uptake, and Proton Conductivity in Radiation-Grafted Proton-Exchange MembranesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2010Sandor Balog Abstract An SANS investigation of hydrated proton exchange membranes is presented. Our membranes were synthesized by radiation-induced grafting of ETFE with styrene in the presence of a crosslinker, followed by sulfonation of the styrene. The contrast variation method was used to understand the relationship between morphology, water uptake, and proton conductivity. The membranes are separated into two phases. The amorphous phase hosts the water and swells upon hydration, swelling being inversely proportional to the degree of crosslinking. Hydration and proton conductivity exhibit linear dependence on swelling. Proton conductivity and volumetric fraction of water are related by a power law, indicating a percolated network of finely dispersed aqueous pores in the hydrophilic domains. [source] Physically and Chemically Cross-Linked Poly{[(maleic anhydride)- alt -styrene]- co -(2-acrylamido-2-methyl-1-propanesulfonic acid)}/Poly(ethylene glycol) Proton-Exchange MembranesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2007lser G. Devrim Abstract Novel proton exchange membranes were solvent-cast from DMF solutions of the terpolymers poly[(MA- alt -S)- co -AMPS], containing hydrophobic phenyl and reactive hydrophilic carboxylic and organo-sulfonic acid fragments with different compositions, and PEGs with different molecular weights and amounts. These membranes were formed as a result of physical (via H-bonding) and chemical (via PEG) cross-linking. The structures of membranes were confirmed by FT-IR and 1H- and 13C NMR spectroscopy. Mechanical and thermal properties, swellability, and proton conductivity of these membranes were significantly affected both by the chemical composition of the terpolymers (mainly the AMPS content) and also the cross-linker (PEG) molecular weight and content in the final form of the membranes. It was concluded that the membranes prepared by using the terpolymer with an AMPS content of 36.84 mol-% and PEG with a molecular weight of 1,450 and with an initial PEG content of 30 wt.-% are the most suitable ones for fuel cell applications. [source] Perfluoroalkyl Phosphonic and Phosphinic Acids as Proton Conductors for Anhydrous Proton-Exchange MembranesCHEMPHYSCHEM, Issue 13 2010Mahesha B. Herath Abstract A study of proton-transport rates and mechanisms under anhydrous conditions using a series of acid model compounds, analogous to comb-branch perfluorinated ionomers functionalized with phosphonic, phosphinic, sulfonic, and carboxylic acid protogenic groups, is reported. Model compounds are characterized with respect to proton conductivity, viscosity, proton, and anion (conjugate base) self-diffusion coefficients, and Hammett acidity. The highest conductivities, and also the highest viscosities, are observed for the phosphonic and phosphinic acid model compounds. Arrhenius analysis of conductivity and viscosity for these two acids reveals much lower activation energies for ion transport than for viscous flow. Additionally, the proton self-diffusion coefficients are much higher than the conjugate-base self-diffusion coefficients for these two acids. Taken together, these data suggest that anhydrous proton transport in the phosphonic and phosphinic acid model compounds occurs primarily by a structure-diffusion, hopping-based mechanism rather than a vehicle mechanism. Further analysis of ionic conductivity and ion self-diffusion rates by using the Nernst,Einstein equation reveals that the phosphonic and phosphinic acid model compounds are relatively highly dissociated even under anhydrous conditions. In contrast, sulfonic and carboxylic acid-based systems exhibit relatively low degrees of dissociation under anhydrous conditions. These findings suggest that fluoroalkyl phosphonic and phosphinic acids are good candidates for further development as anhydrous, high-temperature proton conductors. [source] Layer-by-Layer Hydrogen-Bonded Polymer Films: From Fundamentals to ApplicationsADVANCED MATERIALS, Issue 30 2009Eugenia Kharlampieva Abstract Recent years have seen increasing interest in the construction of nanoscopically layered materials involving aqueous-based sequential assembly of polymers on solid substrates. In the booming research area of layer-by-layer (LbL) assembly of oppositely charged polymers, self-assembly driven by hydrogen bond formation emerges as a powerful technique. Hydrogen-bonded (HB) LbL materials open new opportunities for LbL films, which are more difficult to produce than their electrostatically assembled counterparts. Specifically, the new properties associated with HB assembly include: 1) the ease of producing films responsive to environmental pH at mild pH values, 2) numerous possibilities for converting HB films into single- or two-component ultrathin hydrogel materials, and 3) the inclusion of polymers with low glass transition temperatures (e.g., poly(ethylene oxide)) within ultrathin films. These properties can lead to new applications for HB LbL films, such as pH- and/or temperature-responsive drug delivery systems, materials with tunable mechanical properties, release films dissolvable under physiological conditions, and proton-exchange membranes for fuel cells. In this report, we discuss the recent developments in the synthesis of LbL materials based on HB assembly, the study of their structure,property relationships, and the prospective applications of HB LbL constructs in biotechnology and biomedicine. [source] Time/Space-Resolved Studies of the Nafion Membrane Hydration Profile in a Running Fuel CellADVANCED MATERIALS, Issue 5 2009Valerio Rossi Albertini The hydration profile of proton-exchange membranes (PEM) in running fuel cells (FC) are obtained through an original method that employs very-high-energy synchrotron-radiation X-ray diffraction in space/time-resolved measurements. Determining the amount and spatial distribution of water in the polymeric membrane of PEMFCs under working conditions is of utmost importance in PEMFC technology, since FC performances are strongly dependent on PEM hydration. [source] Synthesis and characterization of sulfonated poly(benzoxazole ether ketone)s by direct copolymerization as novel polymers for proton-exchange membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2007Jinhuan Li Abstract A new series of sulfonated poly(benzoxazole ether ketone)s (SPAEKBO-X) were prepared by the aromatic nucleophilic polycondensation of 4,4,-(hexafluoroisopropylidene)-diphenol with 2,2,-bis[2-(4-fluorophenyl)benzoxazol-6-yl]hexafluoropropane and sodium 5,5,-carbonylbis-2-fluorobenzenesulfonate in various ratios. Fourier transform infrared and 1H NMR were used to characterize the structures and sulfonic acid contents of the copolymers. The copolymers were soluble in N -methyl-2-pyrrolidinone, N,N -dimethylacetamide, and N,N -dimethylformamide and could form tough and flexible membranes. The protonated membranes were thermally stable up to 320 °C in air. The water uptake, hydrolytic and oxidative stability, and mechanical properties were evaluated. At 30,90 °C and 95% relative humidity, the proton conductivities of the membranes increased with the sulfonic acid content and temperature and almost reached that of Nafion 112. At 90,130 °C, without external humidification, the conductivities increased with the temperature and benzoxazole content and reached above 10,2 S/cm. The SPAEKBO-X membranes, especially those with high benzoxazole compositions, possessed a large amount of strongly bound water (>50%). The experimental results indicate that SPAEKBO-X copolymers are promising for proton-exchange membranes in fuel cells, and their properties might be tailored by the adjustment of the copolymer composition for low temperatures and high humidity or for high temperatures and low humidity; they are especially promising for high-temperature applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2273,2286, 2007 [source] Synthesis and properties of novel sulfonated polyimides containing binaphthyl groups as proton-exchange membranes for fuel cellsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2007Yuhan Li Abstract A novel sulfonated diamine monomer, 2,2,-bis(p -aminophenoxy)-1,1,-binaphthyl-6,6,-disulfonic acid (BNDADS), was synthesized. A series of sulfonated polyimide copolymers containing 30,80 mol % BNDADS as a hydrophilic component were prepared. The copolymers showed excellent solubility and good film-forming capability. Atomic force microscopy phase images clearly showed hydrophilic/hydrophobic microphase separation. The relationship between the proton conductivity and degree of sulfonation was examined. The sulfonated polyimide copolymer with 60 mol % BNDADS showed higher proton conductivity (0.0945,0.161 S/cm) at 20,80 °C in liquid water. The membranes exhibited methanol permeability from 9 × 10,8 to 5 × 10,7 cm2/s at 20 °C, which was much lower than that of Nafion (2 × 10,6cm2/s). The copolymers were thermally stable up to 300 °C. The sulfonated polyimide copolymers with 30,60 mol % BNDADS showed reasonable mechanical strength; for example, the maximum tensile strength at break of the sulfonated polyimide copolymer with 40 mol % BNDADS was 80.6 MPa under high moisture conditions. The optimum concentration of BNDADS was found to be 60 mol % from the viewpoint of proton conductivity, methanol permeability, and membrane stability. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 222,231, 2007 [source] Sulfonated naphthalene dianhydride based polyimide copolymers for proton-exchange-membrane fuel cells.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004Abstract A novel sulfonated diamine, 3,3,-disulfonic acid-bis[4-(3-aminophenoxy)phenyl]sulfone (SA-DADPS), was prepared from m -aminophenol and disodium-3,3,-disulfonate-4,4,-dichlorodiphenylsulfone. The conditions necessary to synthesize and purify SA-DADPS in high yields were investigated in some detail. This disulfonated aromatic diamine, containing ether and sulfone linkages, was used to prepare N -methyl-2-pyrrolidinone-soluble, six-membered ring polyimide copolymers containing pendent sulfonic acid groups by a catalyzed one-step high-temperature polycondensation in m -cresol. These materials showed much improved hydrolytic stability with respect to phthalimides. High-molecular-weight film-forming statistical copolymers with controlled degrees of disulfonation were prepared through variations in the stoichiometric ratio of disulfonated diamine (SA-DADPS) in its soluble triethylamine salt form to several unsulfonated diamines. Three unsulfonated diamines, bis[4-(3-aminophenoxy)phenyl] sulfone, 4,4,-oxydianiline, and 1,3-phenylenediamine, were used to prepare the copolymers. The characterization of the copolymers by 1H NMR, Fourier transform infrared, ion-exchange capacity, and thermogravimetric analysis demonstrated that SA-DADPS was quantitatively incorporated into the copolymers. Solution-cast films of the sulfonated copolymers were prepared and afforded tough, ductile membranes with high glass-transition temperatures. Methods were developed to acidify the triethylammonium salt membranes into their disulfonic acid form, this being necessary for proton conduction in a fuel cell. The synthesis and characterization of these materials are described in this article. Future articles will describe the performance of these copolymers as proton-exchange membranes in hydrogen/air and direct methanol fuel cells. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 862,874, 2004 [source] | ||||||||||