Mechanisms and kinetics of the hydrolysis and condensation of alkoxides

Abstract

Hydrolysis and condensation of alkoxides involve different reaction steps. Generally the first step is the dissolution of monomers in organic solvents like alcohols. The second step is hydrolysis, where in most cases condensation may not be separated. Dissolution may incorporate solvatation, coordination, complexation of polymerization. The addition of water leads to hydrolysis of Si-O-C bonds and subsequently condensation of silanoles takes place. Another possibility of reaction is the hydrolysis-free condensation. As a functionof reaction conditions and starting material different possibilities and mechanisms may take place. General conclusions are hardly to be drawn, since the comparison of data is difficult. In the paper theoretical models are reviewed and compared with experimental data. Conclusions with respect to the formation of solid materials are drawn.