Effect of Multiple H-Bonding on the Properties of Polyimides Containing the Rigid Rod Groups

To investigate the influence of hydrogen bonding on the properties of polyimides (PIs) containing rigid rod-like groups, five symmetrical diamines containing benzimidazole, benzoxazole, and hydroxy group were synthesized, and then a series of PIs were prepared. Results showed that hydroxyl-containing poly(benzoxazole imide)s possess higher glass transition temperature (T-g) and dimensional stabilities than their corresponding poly(benzoxazole imide)s. Moreover, the corresponding poly(benzimidazole imide)s presented the best performances, such as the highest T-g, the highest char yield and the highest dimensional stabilities. The influence of hydrogen bonding of benzimidazole on the properties of PIs was stronger than that of hydroxyl groups. Hydroxyl-containing poly(benzoxazole imide) s were formed in crosslinking structures after heat treatment at 400 degrees C. (C) 2015 Wiley Periodicals, Inc.