Preparation And Characterization Of Nitrile-Containing Polyimides And Their Barium Titanate Composite Films

For recent 40 years, polyimides have been developed rapidly and widely applied in many high performance fields, such as aerospace, microelectronics, and elsewhere. Owing to their excellent heat-resistant property, mechanical and dielectric properties, polyimides are one of the most valuable engineering plastics. Introduction of functional groups into molecular chain of polyimides can effectively modify the performance of polyimdes. A series of nitrile-containing polyimides and its composite with barium titanate were prepared and characterized.Firstly, monomer 2,6-Bis(4-aminophenoxy)benzonitrile was synthesized from 4-aminophenol and 2,6-dichlorobenzonitrile. A series of nitrile-containing polyimides were prepared from monomer 2,6-Bis(4-aminophenoxy)benzonitrile with several kinds of dianhydride, for example, PMDA, BTDA, 6FDA, BSAA and BTDA. The structure and properties of polyimides were characterized with FTIR, NMR, TGA, DMTA, et al. The results showed that the nitrile-containing polyimides exhibited outstanding thermal and oxidative stability. With the introduction of nitrile group, the relative dielectric constant of polyimides increased, so nitrile-containing polyimides can be used as the material of film capacitor.Secondly, barium titanate nanoparticles were prepared via direct precipitation method. And silicane coupling agent was used to modify the surface of barium titanate nanoparticles. Then a series of nitrile-containing polyimides/BaTiO3 nanocomposite films were prepared with different barium titanate content. The results indicated that the nitrile-containing polyimides/BaTiO3 nanocomposite films maintained a well thermal and oxidative stability. Their dielectric constant increased obviously and the dielectric loss stayed at a relative low level.