Infrared investigation of the silicon oxide phase in [perfluoro-carboxylate/sulfonate (bilayer)]/[silicon oxide] nanocomposite membranes

[Perfluoro-organic]/[silicon oxide] hybrids were formed by conducting sol-gel reactions of tetraethylorthosilicate within a perfluoro(carboxylate/sulfonate) bilayer membrane in the Co⁺² form. FTIR and ²⁹Si solid-state NMR spectroscopies were used to probe general aspects of molecular structure within the silicon oxide phase as a function of its relative content. The internal gel structure is considerably unconnected in terms of the population of Si O Si groups in cyclic vs. linear substructures and degree of Si atom coordination about bonded SiO₄ units. In situ (HO)_xSiO_2[1-1/4x] intrastructure become increasingly less connected and more strained with regard to bonding geometry with increasing percent silicon oxide. Structural differences are seen between the silicon oxide component incorporated in carboxylate and sulfonate layers. These inorganically modified perfluorinated ionomers have potential as fast-proton conducting membranes for fuel cells and as permselective membranes in liquid pervaporation cells. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 595–606, 1998