(659d) Organic- Inorganic Hybrid Membranes for Gas Separations

The role of a rigid mesoporous substrate on the permselectivity of polymeric membranes was explored by casting thin films of polymers from solution onto commercially available mesoporous alumina supports. Two different polymers, polystyrene and polydimethylsiloxane (PDMS), were used. A 5 wt% solution of the polymer in chloroform solvent was cast onto a glass slide and contacted with the surface of a Whatman Anodisc membrane having a nominal pore size of 20 nm. Excess polymer was removed with solvent before the coated membrane was dried. Single-gas permeation experiments were performed using hydrogen, helium, nitrogen and propane. Interestingly, the selectivity of the gas pairs H2/He, He/N2, N2/C3H8 was increased after modification with polystyrene, indicating the size-selective nature of this glassy polymer. In contrast, the PDMS-modified membranes showed selectivity for C3H8 over N2, indicating the solubility-selective nature of this polymer. Furthermore, the inorganic-organic composite membranes showed better permselectivity properties than pure PDMS. We use various surface characterization techniques to study these new membrane materials and explain their increased performance.