Characterization and mesostructure control of mesoporous fluorinated organosilicate films

Abstract

Mesoporous fluorinated organosilicate films were synthesized from tetramethoxysilane and perfluoroalkylsilanes (RO)₃Si-R′ [R = Me, Et; R′ = (CH₂)₂CF₃, (CH₂)₂(CF₂)₅CF₃, or (CH₂)₂(CF₂)₇CF₃] under acidic conditions in the presence of cetyltrimethylammonium chloride (CTACl) by sol–gel spin-coating. Calcination at 350 °C allowed the removal of surfactants without destroying the other organic contents. X-Ray diffraction patterns of the fluorinated films with short perfluoroalkyl chains indicated that both hexagonal and cubic mesoporous fluorinated organosilicate films can be formed by varying the surfactant to silane mole ratio. On the other hand, the mesoporous fluorinated organosilicate films made from perfluoroalkylsilane with longer perfluoroalkyl chains, which acted as a surfactant, displayed a hexagonal mesostructure across a broad range of surfactant concentrations. Mesoporous fluorinated organosilicate films had higher hydrophobicity and lower refractive indices than mesoporous silica films.