Preparation of Silsesquioxane Particles via a Nonhydrolytic Sol−Gel Route

Abstract

A recently developed method of synthesizing organic−inorganic hybrid (nano)particles using a nonhydrolytic sol−gel route is reported. A range of silsesquioxane particles with diameters in the range ca. 0.1−2.0 μm has been prepared by reacting organotrichlorosilane precursors with dimethyl sulfoxide, used both as an oxygen donor and as a solvent, in the absence of a catalyst under nonaqueous conditions. Pure silica particles with diameters in the range ca. 100−400 nm have been produced by the same method using silicon tetrachloride as a precursor. Ethoxysilane, silanol, and, sometimes, paraformaldehyde groups are present in incompletely condensed species. The formation of silanol groups is insignificant in silsesquioxanes, but not in “unmodified” silicas. A major advantage of this approach is the absence of catalyst residues and, hence, color in the final product in comparison to the normal Lewis acid-catalyzed route.