Polyacrylate effects on tetraethoxysilane polycondensation

The Si-29 NMR spectroscopy was employed in the assessment of polyacrylate effects on the course of acid-catalyzed polycondensation of tetraethoxysilane. The DEFT pulse sequence was used to achieve the sensitivity enhancement required for obtaining qualitatively and quantitatively interpreted Si-29 NMR spectra. Assessment of changes in concentration of reaction products during polycondensation and comparison of mole distribution of chain molecules of reaction systems, which contain different amounts of polyacrylate, has shown that polyacrylate affects polycondensation reactions considerably. The presence of polyacrylate slows up hydrolysis and condensation reactions significantly, and it enhances formation of cyclic products. By this method oligomer distribution changes in the reaction system significantly and the degree of condensation in siloxane gel increases. It is clear that polyacrylate does not act as a single filler, but it changes a structure of siloxane network as well.