CONTRIBUTION TO THE SOL-GEL CHEMISTRY IN SILICA BASED SYSTEMS

摘要

In the present work the sol-gel process in the silica base systems, starting with different alkoxides, was approached by gas chromatography coupled with mass spectrometry (CG-MS). The influence of the type of alkoxide, type of solvent and the water amount on the molecular species formed in the early stages of the hydrolysis-polycondenstion process were analyzed, as well as the influence of the molecular species present in the solution at the moment of gelation on the structure of the obtained gels. In the case of the substituted silicon alkoxides, the hydrolysis-polycondensation reactions are enhanced in the early stages of the process but the condensation is hindered in the final stages, due to the steric effect of the substituents. A substantially higher number of molecular species was formed during of the sol-gel process, when a non-parental alcohol was used. The most stable molecular species toward condensation were established.