Nanostructured Mesoporous Silica Films

The lyotropic liquid crystalline phases of surfactants have been used as templates for the synthesis of mesoporous nanostructured materials. To achieve direct templating by liquid crystalline phases, surfactant concentrations in excess of 30 wt% in water are used. in the case of silicas and metallosilicates the materials are obtained as monolithic objects with typical dimensions greater than 5 mm. Here we report on the processing of thin films of nanostructured mesoporous silicas by dip coating from mixtures that contain high surfactant concentrations. We find that the addition of methanol to the reaction mixture facilitates the formation of uniform, crack-free films. By altering the surfactant to water ratio we were able to obtain films that had micellar cubic (I)), normal topology hexagonal (HI), or lamellar (Lα) organization. Calcination of these films afforded adherent films that in most cases retained the long-ranged architecture of the liquid crystalline phase. The methanol concentration of the dip-coating mixture was observed to have no effect on the structural parameters of the resulting calcined films.