Structure of the Products of Hydrolytic Copolycondensation of 3-Aminopropyltriethoxysilane and 3-Methacryloxypropyltrimetoxysilane: NMR Study

According to 1H, 13C, and 29Si NMR spectroscopy, in the hydrolytic copolycondensation of 3‑aminopropyltriethoxysilane and 3-methacryloxypropyltrimethoxysilane, side reactions of addition of amine groups to methacrylate groups (the Michael reaction), as well as partial hydrolysis and transesterification of ester bonds, occur along with the main process of the formation of oligomeric silsesquioxanes. Depending on the ratio of the starting alkoxysilanes, the oligomers are soluble in water (excess of 3-aminopropyltriethoxysilane) or in organic solvents (excess of 3-methacryloxypropyltrimethoxysilane). Mixed oligomers are capable of gelation at room temperature; the duration of the process increases and the content of the gel fraction decreases with an increase in the proportion of 3-methacryloxypropyltrimethoxysilane units in the oligomer molecules.