The preparation of poly(phenylsilsesquioxane)-polyimide hybrid films was successfully performed with phenyltriethoxysilane (PhTES) and the polyamic acid (polyimide precursor) prepared from 4.4'-oxydianiline (ODA) and pyromellitic dianhydride (PMDA). During the heating process at 300 C, the imidization of the polyamic acid and the sol-gel reaction, hydrolysis and condensation of PhTES, proceeded simultaneously. The IR spectrum and the t3C-NMR and 29Si-NmR spectra showed that the sol-gel reaction of PhTES proceeded in the polymer matrix with high conversion. The hybrid films with a silsesquioxane content up to 75 wt% were obtained as the self-standing form. The hybrid films having a silsesquioxane content of 45 wt% were yellow and transparent, and those having more silicone content were yellow and translucent. The therma] properties of the hybrid films were improved to some extent by the introduction of the silsesquioxane component into the polyimide matrix. With respect to the tensile properties. the tensile strength remained around 85 MPa up to a silicone content of 45 wt%. This value was twice that of the hybrid films based on methyltriethoxysilane. The tensile modulus decreased with increasing silsesquioxane content.
