High dielectric constant polyimide for high-temperature film capacitor by tuning macroconjugated molecule

Polymer film capacitors do not meet the increasing demand of high-temperature (> 125 °C) applications with the rapid development of new energy. In particular, few polymer dielectrics can operate at high temperatures (> 250  °C). In order to develop high-temperature-resistant polymer dielectrics, a novel polyimide containing porphyrin units (PI-a) was prepared by using this diamine polymerized with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BTDA). PI-a possesses high dielectric constant up to 9.04; however, its highly rigid backbone and low molecular weight affect other properties and applications. Here, high-performance polyimide dielectrics were developed by a highly scalable and low-cost strategy. The PI-a and PI-b which was prepared with 4,4′-diaminodiphenyl ether (ODA) and BTDA are mixed by proper design to improve dipolar polarization and intermolecular interactions among polymer chains. Consequently, such polyimide blend with the ratio of PI-a 40% displays an intrinsic giant permittivity of 6.68, low dielectric loss (< 0.05), the highest energy storage density (2.87 J cm −3 ), and possesses excellent mechanical property and excellent thermal stability. These obtained polyimide blends can extend applications of film capacitors at high temperature.