SOL-GEL DERIVED SILICA MEMBRANES WITH TAILORED MICROPOROUS STRUCTURES

The template effect of amphiphilic systems on the porous structure of silica gel layers has been studied. Membranes with a tailor-made microporosity and pore diameters of between 1 and 2 nm were obtained from these gels. Two different preparation methods have been used and their influence on the sol-to-gel transition of silicon alkoxide sols has been investigated. The first method entails the incorporation of non-ionic surfactants which modify the porous structure of gels. Ln this case, specific surface area, pore size and porous volume can be varied in the final material as a function of chain length and concentration of the surfactant. In the second method, self-assembled systems made of cationic surfactants develop during the gelation process and lead to an ordered gel structure. After elimination of the organic mesophase by heating, the membrane material exhibits an ordered microporosity with pore size directly related to the size of the surfactant molecules.