The Importance of a Surface Sis-O-Si Bond between Alkylchlorosilanes and Silica in Defining the Distribution of Water on the Surface

摘要

The surface treatment of siliceous materials with organochlorosilanes has widespread usage in diverse areas as self-assembled monolayers1, chromatography2'3 and xerography.4'5 While the properties imparted by the organosilane are most often dictated by the organo groups, it is generally recognized that the formation of a surface Sis-O-Si bond would be important for obtaining highly robust films. However, a surface Si,-O-Si bond with every adsorbed organosilane may not be needed. A robust film could be attained with few surface bonds between the siloxy network and the surface hydroxyl groups. In this paper, we show that the presence of a covalent bond with the surface SiOH group is a necessary condition to alter the triboelectric properties of the silica. We believe that the surface bonds alter the distribution of water on the surface and the results are explained in terms of a leaky dielectric model in which the charge is dissipated by the formation of a contiguous water layer on the silica. The contiguous water layer is disrupted by the presence of the surface Sia-O-Si bonds.