In this study, silver–polydopamine–hexagonal boron nitride (h-BN@Ag) particles were prepared using mussel chemistry and reducibility of catechol. The modified method was simple and eco-friendly. In addition, we prepared h-BN@Ag/polyimide (PI) composite films via in situ polymerization, the scraper method, and thermal imidization. Owing to the good dispersion of the h-BN@Ag filler particles in the PI matrix and the bridging role of the Ag nanoparticles, the thermal conductivities of the h-BN@Ag/PI composite films were higher than that of the pure PI film. The thermal conductivity of the h-BN@Ag/PI film with the filler content of 10 wt% was 0.382 W (m·K)−1, which was 108% higher than that of pure PI films (0.184 W (m·K) −1). Furthermore, the composite films presented extremely low dielectric permittivity and loss tangent. Moreover, the heat resistance index of the composite films (304.6°C) was higher than that of pure PI (294.3°C). Thus, h-BN@Ag/PI composite films could be promising electronic packaging materials.

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In this study, a polyimide gel material with a high spatial network structure was synthesized. The pyrolysis process increased the material’s porous structure and specific surface area to improve the specific capacitance. The effects of pyrolysis temperature on morphology, structure, thermal, mechanical, and electrochemical properties were studied. The gel material is in the frozen state of the molecular chain from the frozen state to the moving state before 400°C. At the same time, pore structure formation with a weight loss rate of 11.9% in the decomposition state at 400°C–600°C, showing the breakage of the molecular chain and the decomposition of the polymer. With the increase of carbonized temperature, the pore structure becomes more compact while the pore size becomes smaller due to the reconstruction of the polymer structure. Meanwhile, due to the stable formation of carbon skeleton and the increase of carbon amount, the PI gel carbonized material’s thermal conductivity was improved to 1.458 [Formula: see text], which was 330% higher than that of pure PI gel (0.339 [Formula: see text]). Furthermore, the carbonized materials exhibit a specific capacitance of 66.17 [Formula: see text] and show good redox reversibility, apparent concentration polarization and good ion diffusion effect during charging and discharging, suggesting it is a promising electrode material for supercapacitors.