Molecular Regulation of Polyethersulfone Dielectric Composites for Enhanced Dielectric Constant and Energy Storage Performance

In the design of polyether sulfone (PESU)‐based dielectric composites, a molecular regulation strategy was adopted in order to synergistically improve key physical parameters, for instance, energy storage performance and breakdown strength of polymer‐based dielectrics. Pyromellitic dianhydride (PMDA) contains multiple polar carbonyl groups within a rigid conjugated planar skeleton, which can introduce polar sites and charge‐trapping centers within the PESU matrix, making it a promising candidate for high‐performance dielectric energy storage films. Herein, three PMDA/PESU composite films were prepared via the solution blending method, and the PMDA content was adjusted to tailor the interfacial interaction and component compatibility of PESU‐based dielectrics. The gel permeation chromatography (GPC) results verify that the PESU molecular backbone remains intact after PMDA incorporation, without obvious molecular chain scission. The results indicate that the 15 wt% PMDA/PESU composite exhibits relatively superior overall performance, with a relative permittivity of approximately 5.9, a breakdown field strength of 566 kV/mm, and a discharged energy density increased to 8.6 J/cm 3 , superior to the pure PESU dielectric composite. Structural characterization reveals that at this ratio, PMDA and PESU show good compatibility, forming a uniform and dense composite structure. In conclusion, this work provides a feasible molecular regulation approach for designing high‐performance polymer dielectrics, and the resultant 15 wt% PMDA/PESU composite holds great potential for advanced film capacitor applications.