Fabrication and characterization of poly(amide-imides)/TiO₂ nanocomposite gas separation membranes

Nanosized Ti0₂ rich domains were generated in-situ within poly(amide-imide) (PAl) and 6F-poly(amide-imide) (6FPAl) by a sol-gel process. The composite films showed a high optical transparency. The morphology of the Ti0₂ rich domains was observed by transmission electron microscopy (TEM). The Ti0₂ rich domains were well dispersed within the poly(amide-imide) and 6F-poly(amide-imide) matrices and were 5 nm to 50 nm in size. Limited study was also carried out for the fabrication of the P AI/Si0₂ and PAI/fi0₂-Si0₂ composites. It was found that nanosized Si0₂ rich domains were difficult to form within the poly(amide-imide) matrix, although the Si0₂ could be bonded with the Ti0₂, forming nanosized domains within the poly(amide-imide) matrix. The PAI/Ti0₂ composites showed an increased glass transition temperature, and an increased rubbery plateau modulus, in comparison to the unfilled poly(amide-imide). Wide Angle X- ray Diffraction (W AXD) study and Differential Scanning Calorimetry (DSC) analysis suggest that the Ti0₂ filled poly( amide-imide) have a lower crystallinity as compared to the unfilled poly(amide-imide). The dynamic mechanical properties in rubbery regions suggest that Ti0₂ domains function as physical crosslinks, increasing the rubbery plateau modulus with increasing Ti0₂ content. This behavior can be explained by the theory of rubbery elasticity. The actual formation of the nanosized Ti0₂ and Ti0₂-Si0₂ rich domains was explained in terms of hydrogen bonding effects between the polymer, the solvent and the inorganic components.