Effects of inorganic component content on water absorbability and dielectric properties of the doped polyimide film

In this article, nano-doped polyimide/Silica (PI/SiO₂) film was successfully prepared by the hydrolysis and condensation of methyl-triethoxysilane (MTEOS) that served as the precursor of the inorganic moiety and produced the nano-particle of silica in-situ in the polyamic acid (PAA) solution through sol-gel process. The chemical structure of the film was characterized by FTIR. The water absorbability and the dielectric properties including dielectric constant E and dielectric loss t_g of the films were investigated with SiO₂ content. And E and t_g θ of the films were, further, compared heforeafter the films were immersed in deionized water for 24 hours respectively. On the other hand, a certain kind of coupling agent was added in order to improve the compatibility. It turned out that the properties of the nano-doped materials were not only relative to the inorganic component content of the system, but also to the morphology of the phases and the character of interface. The water absorbability of the films decreased with SiO₂ content. And E and t_g θof the films after immersed in water increased than those of the films before the immersion.