Poly(arylene ether)s with sulfonic acid groups on the backbone and pendant for proton exchange membranes used in PEMFC applications

Sulfonated poly(aryl ether) (SPAE) and sulfonated poly(fluorenyl ether ketone) (SPFEK) are synthesized by post-sulfonation and direct polymerization from the sulfonated monomer, respectively. Flexible and smooth proton exchange membranes (PEM) are readily obtained from both polymers, by casting from their 5% solution in N, N'-dimethylacetamide (DMAC) at 60 degrees C. The thermal stability, mechanical strength, and single cell performance of the as-prepared SPAE and SPFEK membranes in a PEM fuel cell (PEMFC) are investigated. The SPAE membrane shows a water uptake of 45% at 80 degrees C and a proton conductivity of 1.02 x 10(-2) S cm(-1), which is close to that of Nafion (R) 115, whereas the SPFEK membrane shows a water uptake of 49% at 80 degrees C and a proton conductivity of 5.37 x 10(-3) S cm(-1). These membranes exhibit a higher mechanical strength, and very good hydrolytic and oxidative stabilities because of their specially designed molecular structures. A single cell evaluation experiment demonstrates the superior cell performance of SPAE compared to that of SPFEK and Nafion (R) 115. These polymers may be a promising proton membrane material for PEM fuel cell applications.