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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O band and relative absorbance intensities of bands of CO group and imide ring (N). 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

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Silica-containing polyimide (PI-Si) crosslinked hybrid films are synthesized and applied to gas separation application. The PI-Si hybrid films are prepared from 4,4 0 -diaminodiphenyl ether (ODA), 3, 3 0 -oxydiphthalic anhydride (ODPA), p-aminophenyltrimethoxysilane (APTS), and phenyltrimetoxysilane (PTS). The monomer of monoamide APTS is used to modulate the block chain length of ODA-ODPA and then form bonding between PTS and ODA-ODPA phases. In the series of xASPI (where x indicates the molecular weight (in kg/mol) of PI block chain length of ODA-ODPA and ASPI denotes PI modified with APTS) hybrid films, the glass transition temperature (T g ) increases and a-relaxation damping peak intensity decreases with the increase of APTS content. Meanwhile, the gas permeabilities of O 2 and N 2 of xASPI films are slightly higher as compared with pure PI. The other series of (5AS-y-S)PI (5ASPI incorporates with PTS and y is the weight of PTS) hybrid films, the properties of T g , density, and a-relaxation damping peak intensity are decreased with increasing the PTS content. However, higher O 2 and N 2 gas permeabilities and O 2 /N 2 selectivity are achieved by increasing the PTS content in (5AS-y-S)PI hybrid films.

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