Preparation and characterization of soluble heat-resistant polyimide films containing bis-N-phenyl-benzimidazole

To prepare soluble polyimides with high temperature resistance, two new diamine monomers, namely, 2,2′-(4,4′-oxybisphenylene)-bis(1-phenyl-5-aminobenzimidazole) (5a), and 2,2′-(4,4′-hexafluoroisopropylidene)-bis(1-phenyl-5- aminobenzimidazole) (5b), were synthesized and exploited to prepare three series of poly(benzimidazole imides)s (PBIIs) by a conventional two-stage synthesis. The resulting PI films were flexible and tough, possessing high glass-transition temperatures (Tgs = 311°C–390°C), improved optical transparency, and excellent solubility. Moreover, the effect of different configuration on performance was revealed, and these data provided a feasible method to enhance both Tg and solubility of PIs by incorporating N-phenyl benzimidazole and corresponding functional moieties.