Preparation of polyimides from pyromellitic dithioanhydride and aromatic diamines

The reaction of phthalic thioanhydride and aniline yielded N ‐phenylphthalimide quite readily. The reaction was strongly dependent on solvent and temperature. Various additives tried as a reaction promoter were almost ineffective. By the extension of the model reaction, polyimides were prepared in a simple one‐step synthesis from pyromellitic dithioanhydride and aromatic diamines in dimethylacetamide or other solvents. Polymers with inherent viscosity up to 0.3 in concentrated sulfuric acid were obtained in approximately quantitative yield.