Homogeneous Polyimide/Silica Nanohybrid Films Adapting Simple Polymer Blending Process: Polymeric Silsesquiazane Precursor to Inorganic Silica

Homogeneous polyimide (PI)/silica nanohybrid films were prepared using acetoxy group functionalized PI and silsesquiazane (SSQZ) as a silica precursor. During the heat treatment at 250 °C in a nitrogen atmosphere, the SSQZ was converted to silica. At the same time, the acetoxy groups of PI were converted into hydroxyl groups and formed covalent bonds with silica to make the resulting hybrid film homogeneous. FE-SEM and AFM analysis showed no evidence of macro-phase separation. As a result, the hybrid films exhibited improved thermal and mechanical properties, including 5% weight loss temperature, residual amount at 1,000 °C, coefficient of thermal expansion, and pencil hardness. The optical properties of the films also improved with showing a similar optical transmittance and lower yellow index.