Characterization of modified silica powders by Fourier transform infrared spectroscopy and cross-polarization magic angle spinning NMR

Silica gel and Cab-O-Sil were chemically modified (silylated) with 3-aminopropyltriethoxysilane and 3-methacryloxypropyltrimethoxysilane under carefully controlled conditions. Subsequently the products were investigated by elemental analysis, Fourier transform IR spectroscopy, and 13C and 29Si cross-polarization magic angle spinning NMR (CP-MAS NMR). The influence of the reaction conditions of the silylation and the effect of subsequent heat treatment and water addition were studied. The resulting differences shed new light on the combined effects of reaction conditions and silica surface structures on the course of the reactions. Some assignments of 29Si NMR signals to specific structures were confirmed, while in one case a reassignment was proposed