Autohomogenization of Polybenzimidazole Composites with Enhanced Mechanical Performance by Air Incorporation

Polybenzimidazoles are one of the most thermally and chemically stable polymers due to their rigid chemical structure with π–π stacking and conjugated bonding. Poly(2,5-benzimidazole) (ABPBI), the simplest structure of polybenzimidazole, was synthesized, but the cast film was not homogeneous and featured thick brown areas, which limited their further application. Silica nanospheres were adapted as porogen to generate nanopores in the ABPBI film by successive etching with hydrofluoric acid. As a result of air-composite formation, the ABPBI film became homogeneous and its surface roughness was reduced from 10.0 to 2.5 nm. The obtained air-composite ABPBI film had more favorable mechanical properties than the original film. An air-composite film prepared with 50 wt % silica content had a tensile strength of 128 MPa and an elongation at break of 23%, both of which values were approximately twice as high as the corresponding values of the original film.