Silica-Based Mesostructured Materials Induced by Surfactant Assemblies in the Two-Dimensionally Limited Space of a Layered Polysilicate Kanemite

Silica-based mesostructured materials derived from a layered polysilicate kanemite were prepared by reactions with gemini-type diammonium (C _16-3-16, C_16-5-16, C_16-3-1) surfactants. The surfactants were assembled in the two-dimensionally limited space between the silicate layers of kanemite, leading to the formation of lamellar, 2-d hexagonal, and disordered mesophases. Lamellar phases were formed by using C_16-3-16 and C_16-5-16 surfactants. An acid treatment of the lamellar C_16-5-16-silicate complex induced the transformation into a 2-d hexagonal phase, whereas the C_16-3-16-silicate complex retained its lamellar structure after the treatment. A disordered phase was obtained through the reaction of kanemite with C_16-3-1 surfactants whose assembly shows a larger surface curvature. The formation of layered surfactant-silicate intermediates under various conditions and the transformation to other mesophases lead to the conclusion that the formation of ordered and disordered mesostructured materials derived from kanemite simply depends on the surfactant assemblies in the two-dimensionally limited space.