Synthesis. structure and properties of polyimide-silica hybrid composites based on biphenyltetracarboxylic dianhydride

摘要

A simple and efficient way of synthesizing nanocomposite films using a dispersion technique is reported, with the resulting films having improved mechanical and thermal properties. Nano-SiO2 was used in a biphenyltetracarboxylic dianhydride-based poly(amic acid) precursor and found to be dispersed up to 7 wt% without any additives. The composites were cast to make 10 μm solid films to establish structure and property relationships between liquid and solid film. The structures of the liquid composite materials were studied using NMR and Fourier transform infrared spectroscopy. Solid film properties such as tensile strength, contact angles and thermal behaviour were evaluated for comparison. The properties of the composite films were found to be enhanced compared to polyimide film itself. Atomic force microscopy and macroscale mechanical measurements showed that composite films with more dipolar bonding interactions have higher elastic moduli and are more deformable. They yield higher adhesion energies, and therefore composite coatings offer greater adhesion. There was a limitation in the film formation beyond 5 wt% of silica.