Rational Design of Soluble Polyaramid for High‐Efficiency Energy Storage Dielectric Materials at Elevated Temperatures

Abstract High‐temperature polymer dielectrics are in great demand for harsh‐environment applications. Maintaining high‐energy storage density and low loss at elevated temperatures remains a major challenge for polymer dielectrics. In this work, a new type of polymer dielectric material is designed, which exhibits comparable dielectric properties in the start‐of‐the‐art dielectric nanocomposites and a superior potential for scale up. A soluble, glassy state polymer with a polarizing group is designed by introducing a weakly polar group into the polyaramid (PA) backbone to dilute the hydrogen bonding of the PA parent species. This increases the mobility of the molecular dipole within the polymer in the glassy state, thereby increasing its dielectric constant while maintaining the high‐temperature performance. The result of this design is a polymer with a glass transition temperature of 251 °C, a dielectric constant of up to 4.5, and a dielectric loss of 1%, while maintaining 2.1 J cm −3 energy density and 86.8% efficiency at 200 °C. This polymer, with its excellent, intrinsic, electrical‐energy‐storage properties can also be adapted for a roll‐to‐roll capacitor film production. Breaking intermolecular hydrogen bonds to enhance the electrical‐energy‐storage properties of polymers is an excellent path for designing polymer dielectrics with high‐temperature capabilities.