POLYACRYLATE EFFECTS ON TETRAETHOXYSILANE POLYCONDENSATION

The Si-29 NMR spectroscopy was employed in the assessment of polyacryl ate effects on the course of acid-catalyzed polycondensation of tetrae thoxysilane. The DEFT pulse sequence was used to achieve the sensitivi ty 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 d istribution of chain molecules of reaction systems, which contain diff erent amounts of polyacrylate, has shown that polyacrylate affects pol ycondensation reactions considerably. The presence of polyacrylate slo ws up hydrolysis and condensation reactions significantly, and it enha nces formation of cyclic products. By this method oligomer distributio n changes in the reaction system significantly and the degree of conde nsation in siloxane gel increases. It is clear that polyacrylate does not act as a single filler, but it changes a structure of siloxane net work as well.