Low-dielectric-constant polyimide aerogel composite films with low water uptake

A polyimide aerogel (PIA) was used to synthesize low-dielectric-constant polyimide composite films. Unlike silica aerogel (SIA) composites, the PIA films were synthesized using polyimide. The resulting films maintained the original thermal and chemical properties of polyimide, which contribute to their homogeneity. The dielectric constant of the aerogel composite film was decreased to ∼2.4, a value similar to that of a SIA composite film. The increase in dielectric constant as a result of water adsorption exhibited by SIA films was counteracted by the hydrophobicity of the polyimide in the PIA film. The PIA composite film exhibited a 3% water uptake, compared with a 29% water uptake in the SIA film, indicating that the polyimide film is the preferred choice in wet conditions. The presence of a uniformly dispersed aerogel, a 1% thermal decomposition temperature of 589 °C and a glass transition temperature of 298 °C for the PIA composite film were confirmed by field emission scanning electron microscopy, thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) analysis, respectively. The TGA and DSC results demonstrated that the excellent thermal properties of polyimide were maintained in the PIA composite film.