Compatibility Enhancement of Polyimide–Silica Hybrid Sol–Gel Materials Without Incorporation of Silane-Coupling Agent

A facile route has been developed to enhance compatibility between organic polyimide matrix and dispersed phase of inorganic silica particles without addition of conventional silane-coupling agent. The as-prepared hybrid sol–gel materials having reduced size of SiO₂ particle dispersed in polyimide matrix were successfully synthesized through pre-catalyzed sol–gel route using an organic diamine base. The PI-silica hybrid materials through conventional polyamic acid-catalyzed sol–gel route with/without silane-coupling agent were also prepared for comparative control studies. Morphological feature of as-prepared sol–gel materials prepared from three different approaches was also compared based on the studies of transmission electron microscopy. Effects of the material composition, in three different catalyzed routes, were investigated by thermal stability, mechanical strength, optical clarity, gas barrier and water absorption measurements of polyimide and a series of polyimide–silica hybrid sol–gel materials, respectively.