STRUCTURAL STUDY OF POLY(PHENYLSILSESQUIOXANE) SOL-GEL MATERIALS

Gels have been prepared via the sol-gel process by cohydrolysis of an organoalkoxide of the type R(n)Si(OR')(4-n) and tetramethoxysilane. Th e influence of organoalkoxide functionality and concentration on the r esulting gel structure has been studied using two organoalkoxysilanes: diphenyldimethoxysilane and phenyltrimethoxysilane. Phenyltrimethoxys ilane-tetramethoxysilane and diphenyldimethoxysilane-tetramethoxysilan e gels structures have been studied by solid-state NMR, small-angle X- ray scattering, and differential scanning calorimetry. The interconnec tion of the networks provided by the organoalkoxysilanes and tetrameth oxysilane has been demonstrated. NMR and SAXS analysis showed that hyb rid gels obtained with the trifunctional alkoxide are more condensed t han the difunctional hybrid The scattering experiments demonstrate the absence of any heterogeneities in the range 10-100 Angstrom. These ma terials have a unique glass transition temperature that indicates the existence of a homogeneous network.