Gas permeation properties of poly(amide-6-b-ethylene oxide)–silica hybrid membranes

The organic–inorganic hybrids of poly(amide-6-b-ethylene oxide) (PEBAX®) and silica were prepared via in situ polymerization of tetraethoxysilane (TEOS) using the sol–gel process and their gas transport properties were studied. The nanodispersed inorganic network produced in the organic matrix was characterized by solid-state 29Si NMR, Fourier transform infrared (FT-IR), dynamic light scattering (DLS) and field emission scanning electron microphotography (FE-SEM). Wide angle X-ray diffraction (WAXD) patterns and differential scanning calorimetry (DSC) thermograms of PEBAX® and hybrid materials revealed that the incorporation of silica induced the structural modification of polymer chains. Gas permeation measurements were accomplished at various temperatures with He, CO2, O2 and N2. These hybrid membranes exhibited higher gas permeability coefficients and permselectivities than PEBAX®, particularly at an elevated temperature. Activation energy of CO2 permeation through the hybrid membranes decreased due to the large contribution of heat of sorption while that of N2 increased resulting from the increase of tortuosity and restricted chain mobility. All these results were explained by the increase of sorption ability of hybrids, attributed to the strong interaction between CO2 molecules and SiO2 domains, additional sorption sites in polyamide block in PEBAX® and the organic/inorganic interphase.