Properties of sol-gel derived silica membranes

Silica membrane materials have been produced by sol-gel processing using tetraethyl orthosilicate as a precursor and oxyethylated fatty alcohols and alkyl phenols as templates. Using low-temperature nitrogen adsorption-desorption, we have studied the adsorption properties and microstructure of silica membranes templated around colloidal surfactant crystals. The results demonstrate that the pore structure of the membranes differs significantly from that of their bulk analogs. The silica membranes have type IV isotherms and an H1 hysteresis loop, characteristic of cylindrical mesopores. The I + IV type mixed isotherms of the bulk analogs are dominated by features of type I with an H2 or H4 hysteresis, characteristic of monodisperse bottle-shaped or slit-like mesopores, respectively.