Synthesis and characterization of new soluble aromatic polyimides from 3,4‐bis(4‐aminophenyl)‐2,5‐diphenylpyrrole and aromatic tetracarboxylic dianhydrides

Novel aromatic polyimides containing tetraphenylpyrrole unit were synthesized from 3,4‐bis(4‐aminophenyl)‐2,5‐diphenylpyrrole and various aromatic tetracarboxylic dianhydrides by the usual two‐step procedure that included ring‐opening polyaddition and subsequent thermal cyclodehydration. These polymers had inherent viscosities in the 0.20–0.65 dL/g range and were practically amorphous as shown by the X‐ray diffraction studies. All the polyimides except for polypyromellitimide were easily soluble in a wide range of organic solvents such as o‐chlorophenol, pyridine, 1,3‐dimethyl‐2‐imidazolidone, N,N‐dimethylacetamide, and N‐methyl‐2‐pyrrolidone at room temperature. These polyimides had high glass transition temperatures of 302–359°C and exhibited 10% weight loss at temperatures above 510°C in nitrogen.