Sol-gel polymerization of bridged polysilsesquioxanes to afford membranes for gas separations

Preparing defect-free, thin films and membranes are key issues in developing a number of energy related technologies, including thin film photovoltaics, membranes for carbon dioxide separation, and hydrogen purification. Hybrid organic-inorganic materials are attractive due to their thermal stability and high degree of functionality. One class of hybrid, the bridged polysilsesquioxanes, combines organic and inorganic phases at molecular length scales. We are investigating development of thin films of bridged polysilsesquioxanes with amine groups as carbon dioxide selective membranes. To create these membranes, we polymerize dilute solutions of the bridged monomers to afford relatively monodispersed, hybrid particles (> 10 nanometers) that are larger than the pores in a mesoporous zirconia support. Ultrathin films are formed by allowing the hybrid organic-inorganic colloid to foul the porosity of the support. In this paper, we will describe the sol-gel chemistry of the bridged monomers, their characterization during sol-gel polymerization by dynamic light scattering and scanning electron microscopy, and our studies of film formation on zirconia supports.