Novel Siloxane-Silica Nanocomposite Aerogels and Xerogels

Novel covalently bonded silicone-silica nanocomposite network materials have been synthesized from a single component molecular precursor. A novel polymeric sol-gel precursor was prepared by hydrosilation of oligo(methylvinylsiloxane) with triethoxysilane and it was applied in sol-gel processing for the synthesis of silicone-silica based gel networks. Acid/base catalyzed hydrolysis and condensation reactions were performed from solutions of the pure macro precursor as well as from mixtures of this precursor with tetraalkoxysilanes followed by either supercritical drying with liquid carbon dioxide or drying at ambient conditions. In both cases monolithic gels as well as powders were obtained and properties such as porosity, surface area and thermal stability have been investigated. Solid state (CP MAS) 29Si-NMR were used to evaluate the chemical composition and extent of condensation of the gels.