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Abstract The solution polycondensation of 3,3′ ‐diaminobenzidine tetrahydrochloride with aromatic dicarboxylic acid derivatives in polyphosphoric acid was found to give high molecular weight polyphenylenebenzimidazoles easily. Their preparation and physical properties, such as thermal stability, solubility, crystallinity, are described.
Iwakura et al. (Mon,) studied this question.