Polyimide/nano-TiO2 hybrid films having benzoxazole pendent groups: In situ sol–gel preparation and evaluation of properties

Abstract

Abstract Polyimide/titania (PI/TiO 2 ) nanocomposite films have been successfully fabricated through the in situ formation of TiO 2 within a PI matrix via sol–gel method. Poly(amic acid) (PAA), which is the precursor of PI, was successfully synthesized by mixing pyromellitic dianhydride (PMDA), with equimolar amount of a diamine monomer having a pendent benzoxazole unit and two flexible ether linkages in N , N -dimethylformamide (DMF) solvent. Tetraethyl orthotitanate [Ti(OEt) 4 ] and acetylacetone were then added to the resulted PAA. After imidization at high temperature, PI/TiO 2 hybrid films were formed. The structure and morphology of the hybrid nanocomposites with different titania contents (0 wt%, 5 wt%, 10 wt%, and 15 wt%) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The results indicate that the TiO 2 nanoparticles were homogeneously dispersed in the hybrid films. The thermogravimetric analysis of nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. Transmission electron microscopy showed that the nanoparticles with an average diameter of 25–40 nm were dispersed in the polymer matrix.