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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.

Polymer film capacitors are ubiquitous in modern electronics and electric systems, but the relatively low working temperatures of polymer dielectrics limit their application in nextgeneration capacitors. The currently reported high-temperature polymer dielectrics rely on the construction of nanocomposites with wide band gap fillers and cross-linked networks to achieve high breakdown strength and high efficiencies. However, generating the optimal chain structure with intrinsic great high-temperature capacitive properties using a onecomponent polymer is still challenging. Herein, a giant discharged energy density in neat polymer has been demonstrated in a series of linear poly(arylene ether amide) (PNFA) at 150 °C, which greatly surpass all the current free-standing dielectric polymer films measured in 10 Hz. The maximum discharged energy density with efficiency above 90% of the PNFA is 2.7 J cm −3 , which is about 3 times that of the state-of-the-art commercial high-temperature polymer films. The architectures of the amorphous polymers have been identified by synchrotron Xray diffraction combined with density functional theory calculations. The origins of superior high-temperature capacitive properties are traced to the increased packing density by the curly-packed chain structure. In addition, the reported polymer could be produced using existing industrial-grade processes, which are economical and practical for large-scale applications.

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