Chemically Modified Poly(vinyl alcohol)−Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) as a Novel Proton-Conducting Fuel Cell Membrane

Polymer blends of poly(vinyl alcohol)−poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PVA−PAMPS) family membranes have been prepared and evaluated as novel proton-conducting materials on the basis of a new concept of binary chemical cross-linking. Chemical cross-linking in pristine PVA−PAMPS with terephthalaldehyde as a cross-linker to form the main chain gives the polymer membrane a very good mechanical property. In addition, by forming the side chains using aldehydes with different spacer lengths as auxiliary cross-linkers, the membranes prepared gain excellent flexibility. PAMPS is “trapped” in the membrane, and provides high proton conductivity (0.12 S cm -1, 25 ± 2 °C) due to the sulfonic acid groups in its chemical structure. The membranes show a larger sorption of nonfreezing water and display an isotropic membrane swelling. Despite their high ion exchange capacity (IEC = 1.68) and high water uptake, the membranes show good water stability. This can be attributed to the high flexibility of the side chains provided by the auxiliary cross-linkers, which allows easy relaxation of the polymer chains.