Synthesis of submillimeter-thick films of surfactant templated mesoporous silica

Submillimeter-thick mesoporous silica films using tetraethoxysilane (TEOS) as a silica source and the hexagonal mesophase of cetyltrimethylammonium ch loride as a template were prepared by solvent evaporation method. The effec ts of H2O/TEOS molar ratio and drying temperatures on the macroscopic morph ology and mesostructure were investigated. Higher H2O/TEOS ratio and higher drying temperature gave a more transparent and smooth-surfaced product. Wi th increasing H2O/TEOS ratio, the order of the mesostructure in the product film was reduced, resulting from the slow formation of surfactant mesostru cture and fast silicate gelation. The pore size showed an increase with inc reasing H2O/TEOS ratio, suggesting mediation by the water layer between the micellar surface and the silicate. The drying temperature affected the rat e of silicate condensation and the solvent evaporation, both factors that i nfluenced the mesostructuralization of surfactant molecules. A high drying temperature facilitated the gelation of silicate rather than the evaporatio n of solvent, resulting in a less ordered mesostructure. (C) 2001 Elsevier Science B.V. All rights reserved.