Polarities of Sol−Gel-Derived Ormosils and of Their Interfaces with Solvents

The effective polarities of a series of organically modified sol−gel silicas and of their interfaces were probed using the solvatochromic dye E T (30) (2,6-diphenyl-4-(2,4,6-triphenyl- N -pyridino)phenolate). The series of materials was obtained by copolymerizing, in various proportions, of methyltrimethoxy-, vinyltrimethoxy-, propyltrimethoxy-, isobutyltrimethoxy- and phenyltrimethoxysilanes with tetramethoxysilane. The various doped Ormosils are solvatochromic toward organic solvents such as various alcohols and toluene. Trends in the polarity variation as a function of the monomer type, of its proportion, and of the solvent at the interface were identified and are discussed. These materials can be used as solvent sensors.