Hybrid films of poly(ethylene oxide-b-amide-6) containing sol-gel silicon or titanium oxide as inorganic fillers: effect of morphology and mechanicalproperties on gas permeability

In this work we describe the preparation of hybrid organic-inorganic films using the sol-gel process. Poly(ethylene oxide-b-amide-6), PEBAX, was used as an organic matrix. Silicon oxide or titanium oxide were prepared by hydr olysis and polycondensation of tetraethoxysilane, TEOS, or titanium tetrais opropoxide, TiOP, respectively. Hybrid films were characterized by electron microscopy, stress-strain tests and their gas permeability and selectivity properties were evaluated. Small angle X-ray scattering was used to invest igate structural heterogeneity caused by the presence of SiO2 or TiO2 parti cles in the organic matrix. For films containing silicon oxide as an inorga nic filler, gas permeability decreased as a function of the inorganic compo nent content. When titanium oxide was used as a filler, gas permeability wa s considerably lower than that measured for films containing silicon oxide (80/20 PEBAX/inorganic precursor compositions). In these cases, the morphol ogies were very similar, but films containing titanium oxide were much more rigid. For CO2/N-2 and CO2/H-2 separation factors up to 52.9 and 7.1, resp ectively, were obtained for 80/20 PEBAX/TiOP films. For higher titanium oxi de contents, gas permeability increased. In these cases, a TiO2 agglomerati on was observed and the barrier performance decreased. Permeability and sel ectivity properties are discussed as a function of morphological and mechan ical properties of these films. (C) 2000 Elsevier Science Ltd. All rights r eserved.