Preparation and physico-chemical characterization of large-mesopore silica thin films templated by block copolymers for membrane technology

Highly selective membranes with controlled porosity can be obtained by growing thin films of mesoporous oxides on an appropriate support. This can be achieved employing organic/inorganic mixed micellar solutions based on metal oxide precursors and commercial templates. In particular amphiphilic block copolymers are very attractive materials as soft-templating agents because they self-assemble into micelles whose morphology and size depend on block composition and solution parameters. Large-mesopore silica films with narrow pore size distribution and high porosity have been obtained by sol–gel reaction of a silicon oxide precursor (TEOS) and using polystyrene-block-poly(ethylene-oxide) (PS-b-PEO) copolymers as templates. In order to modulate size, shape and alignment of the pores, many variables were changed: block copolymer chain length, TEOS/block copolymer ratio, solvent ratio, additives (i.e. polystyrene homopolymer addition). The effect of the different parameters on the porous system was studied by microscopy techniques and gas-volumetric analyses. Final aim of this work is the preparation of silica membranes to be used as selective gates for controlled dosing and transport of chemical species in solution.