Counter diffusion self assembly synthesis of ordered mesoporous silica membranes in straight pore supports

Ordered mesoporous silica membranes in macroporous supports were synthesized by a novel acid catalyzed counter diffusion self assembly method. Mesoporous silica was grown in the pores of the support using tetrabutylorthosilicate and cetyltrimethylammonium bromide as the silica source and surfactant, respectively. The supports used were straight pore, track-etch polycarbonate membranes. Hydrophobic supports with a pore diameter of 5 μm and hydrophilic supports with a pore diameter of 8 μm were used. The grown silica plugs had a highly ordered structure as seen by XRD and TEM studies, with a high surface area of around 990 m2/g and a pore diameter of 2.7 nm. SEM studies and oxygen permeation experiments at constant transmembrane pressure were conducted to assess membrane quality. There was a two order magnitude decrease in the permeance after counter diffusion self assembly growth, showing that good quality membranes were synthesized. The use of hydrophobic supports, support placement and evaporation controlled self assembly are the key factors for the successful formation of these membranes by the CDSA approach.