Reaction of alkylchlorosilanes with silica at the solid/gas and solid/liquid interface

This paper describes the reaction of trichloromethylsilane (TCMS) with a silica surface which contains varying quantities of adsorbed water. The reactions have been studied using IR spectroscopy at both the solid/gas interface and the solid/liquid interface. The studies at the solid/liquid interface have been enabled by the design of a cell which permits an in situ study of the reaction as well determining which of the observed species are actually adsorbed on the surface and which are in the solution phase. It is concluded that TCMS does not react directly with the surface silanols of a dehydrated silica at room temperature. At the solid/gas interface, the TCMS is hydrolyzed by surface water and methyltrisilanol is formed. The methyltrisilanol is adsorbed on the surface and does not polymerize or form a siloxane bond with the surface silanols. At the solid/liquid interface, however, the methyltrisilanol condenses to form a polymeric layer which becomes adsorbed on the surface.