Nobel block poly(arylene ether) ionomers for high temperature and low humidity operable fuel cells

We report herein novel series of aromatic ionomers as alternative membranes for polymer electrolyte fuel cells (PEFCs). Poly(arylene ether) ionomers containing high local concentration of sulfonic acid groups in the hydrophilic component have been synthesized via nucleophilic substitution polymerization followed by the sulfonation reaction. The obtained block copolymer membranes contained fully sulfonated fluorenylidene biphenylene groups (four sulfonic acid groups per repeating unit) and showed very unique and pronounced hydrophilic/hydrophobic phase separation. The membranes showed high proton conductivity, comparable to that of Nafion (perfluorinated ionomer membrane), even at low humidity. The longer hydrophilic block length resulted in the higher proton conductivity. Hydrogen/air fuel cell could be successfully operated at 100 degree C and 30% relative humidity (RH). Thermal, chemical, and mechanical stability, and gas permeability will also be presented.