Solid-state silicon-29 and carbon-13 NMR spectroscopy using cross-polarization and magic-angle-spinning techniques to characterize 3-chloropropyl and 3-aminopropyl-modified silica gels

Abstract

Solid-state silicon-29 and carbon-13 NMR spectroscopy, using cross-polarization and magic-angle-spinning techniques (CP-MAS), have been utilized to characterize 3-chloropropyl and 3-aminopropyl-modified silica and derivatives. The results have been supplemented with data obtained from elemental analysis. Using silicon-29 NMR solid-state spectroscopy, it has been found possible to discriminate three different types of surface bonds, i.e., covalent linkages between the organosilane moiety and one, two, or three silanol groups. For the 3-aminopropyl modification additional structural information was obtained from solid-state carbon-13 NMR. The change in chemical shift of the β-methylene carbon reflects environmental influences. Methoxy resonances, originating from adsorbed methanol molecules and/or unhydrolyzed methoxysilane functions, were identified in both types of modified silicas.