As a common two-dimensional carbon material, graphene has been widely doped into polymers to prepare high-performance dielectric materials. However, the shortcomings of graphene, such as large specific surface area and poor dispersion, limit its further application. Therefore, in this work, to solve the problem regarding the uniform dispersion of graphene in the matrix, in situ polymerization was used to prepare graphene/polyimide films, in which 1,4-diiodobutane was used as a reduction agent to prevent the aggregation of graphene oxide (GO) during imidization. High dielectric constant composite films were obtained by adjusting the ratio of 1,4-diiodobutane in GO. The results show that the resulting graphene/polyimide composite film possessed a dielectric constant of up to 197.5, which was more than 58 times higher than that of the polyimide (PI) film. Furthermore, compared to the pure PI film, the composite films showed better thermal stability and mechanical properties. Thermal performance tests showed that the 1,4-diiodobutane added during the preparation of the composite film was thermally decomposed, and there was no residue. We believe our preparation method can be extended to other high dielectric composite films, which will facilitate their further development and application in high power density energy storage materials.

Polyimide (PI) is widely used in the field of microelectronics because of its excellent thermal, mechanical, optical, and electrical properties. With the development of electronics and information industry, PI as a dielectric material needs to possess low dielectric loss. PI/carbon quantum dots (PI/CQDs) composite films with low dielectric loss were prepared by introducing CQDs into PI matrix. At 25°C and 1 kHz voltage, the dielectric loss of pure PI film is about 0.0057. The dielectric loss of PI/CQDs composite film is about 0.0018, which is about 68% lower than that of pure PI film. The dielectric loss of PI/CQD composite film is greatly reduced while the mechanical properties and thermal properties of PI/CQDs composite film roughly remain unchanged. Due to the cross-linking structure formed between CQDs and PI molecular chain, the relative movement of PI molecular chain is hindered.