Synthesis, properties, and fuel cell performance of perfluorosulfonated poly(arylene ether)s

Poly(arylene ether)s containing superacid groups (FSPEs) were synthesized as proton conducting membranes for fuel cell applications. To obtain the title ionomers, a series of brominated poly(arylene ether)s were synthesized and perfluorosulfonated via Ullmann coupling. The chemical structure and the ion exchange capacity (IEC) of the FSPEs were characterized by ¹H and ¹⁹FNMR spectra. Tough, flexible, and transparent membranes with the IEC ranging from 0.34 to 1.29 mequivg^-1 were obtained by solution casting. The FSPE membranes did not show obvious glass transition behavior up to the decomposition temperature (180 °C). Microscopic analyses revealed homogeneous and well-connected ionic clusters for the high IEC membrane. Compared to conventional sulfonated poly(arylene ether) membranes, the FSPE membranes showed much higher proton conductivity. The highest proton conductivity of 0.07 S cm^-1 was achieved at 80 °C and 86% relative humidity (RH) with the IEC = 1.29 mequivg^-1 membrane. A fuel cell using the FSPE membrane showed comparable performance to that of a Nafion cell at 78% RH and 80 °C.