Nanoporous and proton conductive hydrophobic-hydrophilic copolymer thermoset membranes

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 48; no. 12; pp. 1245 - 1255
• Main Authors: Rahmathullah, M. Aflal M, Snyder, Joshua D, Elabd, Yossef A, Palmese, Giuseppe R
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.06.2010; Wiley
• Subjects: Applied sciences; bisphenol A; carbon dioxide; composite polymers; conducting polymers; copolymerization; Copolymers; crosslinking; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Exchange resins and membranes; Forms of application and semi-finished materials; Fuel cells; hydrophilicity; hydrophobicity; ion exchange; Membranes; Moles; Monomers; Nanostructure; network copolymers; networks; Organic polymers; Physicochemistry of polymers; Polymer industry, paints, wood; Polymers with particular properties; Porosity; Preparation, kinetics, thermodynamics, mechanism and catalysts; proton conductivity; Solvents; Sulfonic acid; sulfonic acids; Technology of polymers; Voltage current curve; Porous membrane; Polymer solid electrolyte; Composition effect; Acrylamide derivative copolymer; Nanoporous materials; Property processing relationship; networks; Bound water; Sulfonate copolymer; Free water; Water content; Proton conductivity; fuel cells; Supercritical fluid extraction; Proton exchange membrane fuel cells; copolymerization; Electrical properties; conducting polymers; Experimental study; membranes; Alcohol copolymer; Ion mobility; network copolymers; Morphology; Preparation; Cation exchange membrane; Methacrylate copolymer; Radical copolymerization; crosslinking
• ISSN: 0887-6266; 1099-0488; 1099-0488
• DOI: 10.1002/polb.22002

Copolymers of hydrophobic diglycidyl ether of bisphenol A (DGEBA) vinyl ester (VE) and hydrophilic 2-acrylamido 2-methyl 1-propane sulfonic acid (AMPS) were evaluated as proton conducting membranes for fuel cell applications. Membranes were synthesized using free radical copolymerization in the presence of a common solvent for both monomers, dimethyl formamide (DMF), followed by solvent removal by supercritical CO₂ to induce porosity. Micrographs revealed pore sizes below 60 nm with porosity proportional to the initial solvent fraction used. Studies on the states of water showed that the presence of this pore volume significantly altered the freezable water fraction at equivalent AMPS concentrations. Comparison of the moles of water per mole of sulfonic acid (λ) between copolymer membranes and AMPS monomer solutions showed that the nonfreezable water (λ|nonfr) was depressed at high AMPS concentrations, suggesting that differences in interatomic distances between sulfonic acid groups might alter λ|nonfr. The highest average through plane conductivity of membranes was determined to be 30 mS/cm and was comparable to that of Nafion®117 (27 mS/cm). The effective proton mobility, μeff, was calculated and suggested to be a parameter used to capture the effects of membrane structure and swelling while acting as a comparison between different membrane types. Fuel cell tests on membranes at low ion exchange capacities were compared to Nafion®117, with suggestions on improvements of copolymer structures for improved performance.