Synthesis and properties of copoly(pyromellitimide–benzimidazopiperidone)

Some new polymers and model compounds were obtained from the reaction of N,N‐protected glutamic anhydride with primary amines and the ring‐opening reaction was proved to belong to γ‐orientation. When the primary amine is aromatic ortho‐diamine, it was proved that the reaction route of ring‐closure dehydration of the ring‐opening addition products was through imidazolecarboxylic acid rather than imide amine, and at the last step it becomes imidazopiperidone. The corresponding polymer containing pyromellitdiimide and benzimidazopiperidone in the main chain was synthesized by a three‐step reaction of 2,2′‐pyromellitdiimidodiglutaric anhydride with 3,3′‐diaminobenzidine. In the first step, polyaminoamic acid having pyromellitdiimide ring was prepared in polar solvents. In the second step, the conversion of polyaminoamic acid to the copolyimidoimidazole acid was carried out thermally in solution or solid at 140–200°C. At last, the conversion of copolyimidoimidazole acid to the copolypyromellitimidobenzimidazopiperidone was performed either thermally (300°C) or by chemical means. Infrared spectra and NMR spectra were studied and compared with corresponding model compounds. Form solubility and TG analysis, the polymer belongs to a heat‐resistant polymer.