Influence of water in the reaction of γ-aminopropyltriethoxysilane with silica gel. A Fourier-transform infrared and cross-polarisation magic-angle-spinning nuclear magnetic resonance study

Abstract

Silica gel has been modified with γ-aminopropyltriethoxysilane under varying conditions, controlling the influence of water in the different modification stages. Diffuse reflectance infrared Fourier-transform (DRIFT) spectra revealed the influence of surface water in the reaction stage and of air humidity in the curing stage. These results were confirmed and refined by 29Si and 13C cross-polarisation magic-angle-spinning nuclear magnetic resonance (CPMASNMR) spectroscopy. Combining the results of both techniques, four modification structures present on the silica surface are proposed, depending on the conditions used.