SYNTHESIS AND CHARACTERIZATION OF INORGANIC GELS IN A LYOTROPIC LIQUID-CRYSTAL MEDIUM .2. SYNTHESIS OF SILICA-GELS IN LYOTROPIC CRYSTAL PHASES OBTAINED FROM CATIONIC SURFACTANTS

Microporous silica materials with tailored porosity are synthesized by the sol-gel process using lyotropic liquid-crystal phases as template s. The starting isotropic sol is obtained by mixing tetramethoxysilane , water and an alkyltrimethylammonium bromide. The polymerization of t he silica network and the formation of the amphiphilic mesophase are s imultaneous and cooperative. After thermal elimination of the surfacta nt molecules, an ordered porous texture is maintained in the silica ma terial. The pore size is related to the size of the templating unit an d modulated by the length of the alkyl chain of the used surfactant. I n this paper, the various steps of the synthesis are studied and the p orous texture of the final material is characterized and discussed in terms of templating effects.