Autohomogenization\nof Polybenzimidazole Composites\nwith Enhanced Mechanical Performance by Air Incorporation

Polybenzimidazoles are one of the most thermally and\nchemically\nstable polymers due to their rigid chemical structure with π–π\nstacking and conjugated bonding. Poly(2,5-benzimidazole) (ABPBI),\nthe simplest structure of polybenzimidazole, was synthesized, but\nthe cast film was not homogeneous and featured thick brown areas,\nwhich limited their further application. Silica nanospheres were adapted\nas porogen to generate nanopores in the ABPBI film by successive etching\nwith hydrofluoric acid. As a result of air-composite formation, the\nABPBI film became homogeneous and its surface roughness was reduced\nfrom 10.0 to 2.5 nm. The obtained air-composite ABPBI film had more\nfavorable mechanical properties than the original film. An air-composite\nfilm prepared with 50 wt % silica content had a tensile strength of\n128 MPa and an elongation at break of 23%, both of which values were\napproximately twice as high as the corresponding values of the original\nfilm.