Preparation Of PI/SiO₂ Nano-hybrid Film By Sol-gel Process And Study On Its Structure And Properties

The compatibility problem of polyimide/silica was solved by using the water yielded in the cycloimidization of polyamide acid which could control the hydrolysis-condensation of TEOS.The polyamide acid was synthesized from PMDA and 4,4-ODA, and its imidization process was traced by IR. The result showed that imidization began at 80 ℃ and completed at 300℃.Without additional water, the PI/SiO2 hybrid films were prepared from TEOS and PAA by sol-gel; the PI/SiO2 hybrid films with different content of additional water or different content of coupling agent were also prepared to compare with the nonaqueous PI/SiO2 hybrid films. All the films were characterized by TEM, mechanical properties, TGA and DMTA, absorption water and dielectric properties. The result indicated that with the increasing of silica, the size of the silica particles raised; the incorporation of the additional water made the size of the silica particle increased at the same content of silica; when contacted with the water in the air, the size of the silica particle changed from inner to surface gradually; the coupling agent can reduce the size of the silica particle.