Synthesis of novel colorless polyimides from benzimidazole diamines with various linearity

To synthesize colorless superheat-resistant polyimide films, one of the valid approaches is the incorporation of the asymmetric and warped structures in the main chain. Applying this approach on 5(6)-amino-2-(4-aminobenzene)benzimidazole (PABZ) and changing its linearity, 6, 5 '-diamine-2 '-methyl-1-methyl-2-phenylbenzimidazole (5a) and 6, 3 '-diamine-2 '-methyl-1-methyl-2-phenylbenzimidazole (5b) were devised and synthesized successfully, then polymerized with 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA). The prepared poly(benzimidazole imide)s (PBIIs) with the rigid main chain and loose packing had the excellent heat-resistant level (T-g > 400 degrees C) and optical properties (T-400 > 80%). Besides, the alterations resulting from various linearities were discussed comprehensively. This research is beneficial to the application of optical field, providing a promising candidate of heat-resistant colorless materials.