Preparation and characterization of fluorine-containing benzimidazole polyimide films with a micro-branched crosslink structure

In order to solve the problem of high-water absorption and low transparency of benzimidazole polyimide (PBII) films, this study introduced fluorine-containing groups into the benzimidazole polyimide molecule chains, and a series of benzimidazole polyimide films with different fluorine-containing ratios were prepared. In addition, a micro-branched crosslinking structure was established by adding triamino compounds to the system, and the effect of the micro-branched crosslinking structure on the film properties was investigated. The research showed that adding a certain amount of fluorine-containing groups could effectively improve the optical properties and decrease water absorption of polyimide films while having a small effect on the heat resistance and thermal dimensional stability. The incorporation of a small amount of triamino compounds effectively compensated for the adverse effects on the mechanical properties, heat resistance, and thermal dimensional stability caused by the addition of fluorine-containing groups and lowering the imidization temperature. In addition, the water absorption could be further reduced by establishing a cross-linked structure. In this study, a new design idea was provided to achieve the balance of heat resistance, thermal dimensional stability, water absorption, transparency, and mechanical properties of benzimidazole polyimide films.