Polyimide film containing sulfone groups with high dielectric properties

Polyimide dielectric film are highly demanded in the modern electronics industries and power systems at high temperature, but its low energy storage density severely limits their applications. In this paper, a kind of polyimide dielectric film was fabricated by copolymerization of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and 2-(4-amino-phenyl)-5-amino benzimidazole (BIA) with the introduction of 4,4′-diamino phenyl sulfone (DDS). With the increase of DDS contents, the dielectric constant of polyimide film could be improved to 4.45, and the dielectric loss angle remained below 5*10−3 within frequency of 1 Hz–103 Hz. The simulated molecular structure showed that the introduction of the sulfone groups could increase the chain spacing with larger free volume fraction, which facilitates a synergistic increase in dielectric constant while reducing dielectric loss. A high energy density of 3.27 J/cm3 at 380 MV/m at room temperature could be achieved by loading a small amount of 15mol% DDS. In addition, the film keeps good dielectric properties at high temperatures with the dielectric loss of 0.026 at 150 °C and 1 kHz. And the film can also maintain a high breakdown strength with an energy density of 1.14 J/cm3 at 260 MV/m and the efficiency of 74% at 150 °C, indicating its good potential for polymer film capacitors at high temperature.