Polybenzimidazoles. II

Abstract

Abstract A polybenzimidazole has been prepared from 3,3′‐diaminobenzidine and phthalic anhydride which has a high molecular weight and very good heat stability. Replacement of the hydrogen atoms on the nitrogen of the imidazole nuclei in a polybenzimidazole does not improve the heat stability as indicated by the properties of poly‐2,6‐( m ‐phenylene)‐3,5‐diphenyldiimidazobenzene. Polybenzimidazoles with aliphatic units have been prepared from 3,3′‐diaminobenzidine and the diphenyl ester of succinic and glutaric acids. The diphenyl esters of oxalic and malonic acids did not yield polymers presumably because cyclic amides were formed. Further hydrolytic stability tests on polybenzimidazoles have been reported. Some model compounds have been prepared for comparison of their melting points and absorption spectra with those of the corresponding polymer.