Hydrolysis–condensation reactions of diethylphosphato-ethyltriethoxysilane with tetraethoxysilane studied by 29Si-NMR: Solvent and phosphonate catalytic effect

Hydrolysis and condensation reactions of diethylphosphato-ethyltriethoxysilane (SiP) and a mixture of SiP and tetraethoxysilane (TEOS) have been studied in ethanol and N-methylacetamide (NMA) as solvent. Conditions of reaction used for both SiP and SiP/TEOS mixture were Si/solvent (ethanol or NMA)/water molar ratio equals to 1/20/5 at 30 °C and without addition of external catalyst. The reactions have been investigated by high resolution 29Si nuclear magnetic resonance (NMR). The hydrolyzed and condensed species, from SiP and TEOS were identified and quantified for both solvents as a function of reaction time. The influences of the amide medium as well as the catalytic effect of the phosphonate function of SiP on TEOS hydrolysis were established.