Preparation of Polyimide/Silica Hybrid Composites Based on Polymer‐Modified Silica Gel

With a view to improve the affinity of silica particles for the polymer matrix, a new type of polyimide/silica (PI/SiO2) hybrid composite films has been successfully prepared using the polymer‐modified silica gels. First, poly(maleic anhydride‐co‐styrene)/silica [P(MA‐ST)/SiO2], polymer‐modified silica gels, were prepared by the condensation reaction of the surface hydroxyl group of silica gel with a polymeric coupling agent, P(MA‐ST)–trimethoxysilane. Then, PI/SiO2 hybrid films of different silica contents were obtained by the blending of polymer‐modified silica gels with poly(amic acid) (PAA) from pyromellitic dianhydride (PMDA) and 4,4′‐diaminodiphenyl ether (ODA) in N‐methyl‐2‐pyrrolidinone (NMP). The decomposition temperature at 5 wt% loss (Td5) of the hybrid films, as measured by thermogravimetric analyses (TGA), increased with the increasing P(MA‐ST)/SiO2 content within the measured range. The PI/SiO2 hybrid films with ca. 5 wt% of modified‐silica exhibited balanced mechanical properties, whereas the hybrid films with higher silica contents had reduced mechanical properties, as confirmed by the scanning electron micrographs (SEM) observation.