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Morphology, thermal properties, hydrophobicity and O2/N2 gas separation performance of 4,4′-oxydiphthalic anhydride-based polyimide/titania hybrids



Two 4,4′-oxydiphthalic anhydride (ODPA)-based polyimide (PI)/titania hybrid films with different morphologies were prepared through an in situ sol-gel process. The precursor, poly(amic acid) (PAA), was synthesized using ODPA, diamine of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) or 4,4′-diaminodiphenyl ether (ODA) and a suitable amount of dimethylformamide solvent. A mixture of tetraethylorthotitanate (Ti(OEt)4) and acetylacetone with molar ratio of 1:4 was then added to the PAA solution and mixed thoroughly. Following curing, PI/titania hybrid membranes with different crosslinkages and Ti(OEt)4 contents were prepared. PI hybrids with the longer BAPP diamine present different morphologies and property changes related to the Ti(OEt)4 content from those of hybrids with the shorter ODA diamine. The morphologies of the two ODPA-based PI/titania hybrids were studied with reference to the disruption of imide ring formation. Different crosslinked structures produced were identified using Fourier transform infrared analysis from the frequency shift of the C[DOUBLE BOND]O band and relative absorbance intensities of bands of C[DOUBLE BOND]O group and imide ring ([BOND]N[DOUBLE BOND]). Thermal properties, O2/N2 gas separation performance, contact angle, storage modulus, glass transition temperature and decomposition temperature of the PI hybrids were all found to be functions of the Ti(OEt)4 content, crosslinked structure and PI type. Copyright © 2012 Society of Chemical Industry