Nuclear Magnetic Resonance Studies of the Hydrolysis and Molecular Motion of Aminopropylsilane

The hydrolysis and dynamics of silane coupling agents have been probed using nuclear magnetic resonance (NMR) spectroscopy. The hydrolysis of γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane were studied using proton NMR spectroscopy. The rates of hydrolysis were dependent on the water and silane coupling agent concentration as well as their chemical nature. The methoxy-substituted silane hydrolyzed much faster than the ethoxy-substituted one. The molecular motion of γ-aminopropylsilane-d2 immobilized on a silica surface and as the bulk polymerized siloxane were characterized by 2H solid-echo NMR techniques. It was found that the motion of the silane coupling agent on silica was more restricted than in the condensed polymer. Deuterium oxide exchange experiments also showed that the motion of deuterons on the amino group is much faster than those of the deuterons on the methylene group in silane coupling agents. © 1990