THE CHEMICAL-KINETICS OF SILICATE SOL-GELS - FUNCTIONAL-GROUP KINETICS OF TETRAETHOXYSILANE

The functional group chemical kinetics of tetraethyoxysilane (TEOS) have been investigated by Si-29 NMR. The functional group analysis treats the concentration of the various functional groups (alkoxy, silanol and Si-O-Si bond) without reference to how they are distributed about the various silicon atoms. The functional group kinetics address the overall reaction pathways and the reaction mechanism. Previously, tetramethoxysilane (TMOS) was found to undergo acid-catalyzed reaction via both water- and alcohol-producing condensation processes. Acid-catalyzed TEOS condensation proceeds via only the water-producing reaction. These differences in the chemical kinetics of TMOS and TEOS affect the dependence of condensation rates on the water-to-silicon ratio of the solution.