A Si-29 NMR study of the sol-gel polymerisation rates of substituted ethoxysilanes

Si-29 nuclear magnetic resonance spectroscopy has been used to generate reaction profiles for the acid-catalysed hydrolysis and condensation of various substituted ethoxysilanes which may be used in sol-gel processes. Experiments were performed at acid concentrations that enabled hydrolysis rate determinations to be made both with and without the influence of the condensation process. The relative rates of both hydrolysis and condensation reactions were generally predictable when the electronic and steric effects of the substituents were considered.