Polybenzimidazoles were synthesized from 3,3'-diaminobenzidine (DAB) and dicarboxylic acids. The polymerizations using the dicarboxylic acid monomers were carried out in polyphosphoric acid (PPA) and phosphorus pentoxide/methansulfonic acid (PPMA) which acted as the solvent and condensing agent. The resulting polybenzimidazoles had inherent viscosities in the range of 0.12 to 0.84 dL/g....