| Abstract: | A new sequence isomer of AB‐polybenzimidazole (AB‐PBI) was developed as a candidate for high‐temperature polymer electrolyte membrane fuel cells. A diacid monomer, 2,2′‐bisbenzimidazole‐5,5′‐dicarboxylic acid, was synthesized and polymerized with 3,3′,4,4′‐tetraaminobiphenyl to prepare a polymer that was composed of repeating 2,5‐benzimidazole units. In contrast to previously prepared AB‐PBI, which contains only head‐to‐tail benzimidazole sequences, the new polymer also contains head‐to‐head and tail‐to‐tail benzimidazole sequences. The polymer was prepared in polyphosphoric acid (PPA) and cast into membranes using the sol–gel PPA process. Membranes formed from the new AB‐PBI were found to be mechanically stronger, possessed higher acid doping levels, and showed improved fuel cell performance, when compared to the previously known AB‐PBI. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 |
