Develpment of highly selective silica membranes obtained by using PS-b-PEO as templates

Highly selective membranes with controlled morphology can be obtained by growing thin mesoporous oxide films on an appropriate support. This can be achieved employing organic/inorganic mixed micellar solutions based on the use of proper templates. Amphiphilic block copolymers are very attractive materials for soft-templating. When mixed with organic solvents selective for one of the blocks, they can self-assembly into micelles with the insoluble blocks constituting the micellar core and the soluble ones the corona. The silica porous membranes described in this contribution were obtained by sol-gel reaction of a silicon oxide precursor (TEOS) and using polystyrene-block-poly(ethylene-oxide) (PS-b-PEO) copolymers as templates. Morphology and size of the self-assembled micelles and of the final porous oxide depend both on composition parameters (such as the length and nature of the polymer blocks) and on solution parameters (such as the hydrophilic/hydrophobic balance between solvents and cosolvents). This contribution focuses on the effect of composition parameters, namely the chain length of each polymer block, the stoichiometric ratio of the monomers, and the polymer/silica ratio. By changing these parameters silica structures with narrow pore size distribution and pore shapes ranging from spheres to channels were obtained. The final goal of this research will be the preparation of silica membranes with controlled and high porosity to be applied in the field of microfluidic analyses (e.g. Lab-on-a-chip devices) and as selective gates in microchip-based technologies for separation, detection and dosing of molecular or ionic species, charged nanoparticles and biomolecules.