Preparation and characterization of heat-resistant polyimide/titanium dioxide nanocomposite films containing triptycene side units by sol–gel processes

Abstract

Thermally stable polyimide/titanium dioxide (PI/TiO₂) hybrid nanocomposite films have been successfully synthesized through the in situ formation of TiO₂ within a PI matrix via sol–gel process. Poly(amic acid) (PAA) solutions are prepared from bis(4-aminophenoxy)phenyl triptycene and 3,3′,4,4′-benzophenone tetracarboxylic dianhydride in N-methyl-2-pyrrolidinone solvent. The different amounts of tetraethyl orthotitanate and actylacetone (acac) are incorporated into PAA matrix, and then thermally imidized to form PI/TiO₂. The chelating agent, acac, was applied to reduce the gelation rate of titanium alkoxide. Thermal decomposition temperatures with a 10% weight loss are in excess of 510°C, and char yields at 800°C under nitrogen atmosphere are higher than 69%. The chemical and morphological structures of the hybrid nanocomposites were characterized using Fourier transform infrared spectroscopy, x-ray diffraction, and transmission electron microscopy. The results show that the TiO₂ particles are well dispersed in the PI matrix with particle size between 10 and 30 nm in diameter.