• 2,2′-bisbenzimidazole-5,5′-dicarboxylic acid;
  • AB-PBI;
  • high temperature materials;
  • i-AB-PBI;
  • poly(2,5-benzimidazole);
  • polybenzimidazole;
  • polycondensation;
  • polyelectrolytes;
  • polymer electrolyte membrane fuel cells;
  • step growth polymerization


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