Development of novel coatable compatibilized polyimide-modified silica nanocomposites

A series of novel coatable polyimide silica (PI-SiO₂) nanocomposites have been synthesized. A new PI matrix, containing pendant hydroxyl groups, was prepared reacting diamine monomers (4,4'-diamino-4"- hydroxytriphenylmethane, and 4,4'- oxydianiline) and pyromellitic dianhydride (PMDA). Whereas, silica reinforcement was generated using TEOS. A coupling oligomeric species 2,6-bis(3-(triethoxysilyl)propyl)pyrrolo[3,4- f]isoindole-1,3,5,7(2H,6H)-tetraone (APA) was used to furnish silica nanoparticles with imide linkages and hydroxyl groups. As these groups are already present in PI matrix, so their presence in nanoparticles brought structural similarity, and hence enhanced phase connectivity among two phases. The resulting PI-SiO₂ hybrids, with improved interfacial interactions through hydrogen bonding and like-like chemical interactions, displayed much enhanced morphological, thermomechanical, and thermal properties. The properties of resulting hybrids were studied by various advanced techniques and compared with PI-SiO₂ hybrid system which was prepared from same polyimide and unmodified silica network.