Synergistic enhancement of high-temperature dielectric energy storage in polyisopren-imide based polymers via fluorination and dual physical-chemical crosslinking

High-temperature applications demand polymer dielectrics with a high glass transition temperature ( T g ), wide bandgap, and high dielectric constant for superior energy storage performance. However, inherent trade-offs among these key parameters in existing polymers lead to soaring leakage currents and increased energy losses at elevated temperatures, severely limiting further performance enhancement. To address this issue, this paper uses polyisopren-imide (PNI) as the matrix material, attempting to decouple the T g , bandgap, and dielectric constant using fluorination modification and the creation of physical-chemical double-crosslinked networks. First, electron-withdrawing fluorine atoms were incorporated into PNI to form FPNI 50 , enhancing the polymer's bandgap and thereby inhibiting charge excitation and reducing leakage current. Subsequently, dicyclopentadiene (DCPD) was employed as a chemical crosslinking agent to construct a covalent-bonded crosslinked network (FPNI 50 D 5 ) which effectively restricted molecular chain mobility and reduced dielectric loss. Finally, 4,4-dihydroxy dicyclohexane (BCHD) was introduced to form physical crosslinking via hydrogen bonding between hydroxyl groups and fluorine atoms. BCHD, featuring high polarity and a wide bandgap (8.84 eV), enhances the dielectric constant of the polymer while simultaneously suppressing carrier transition. Consequently, the FPNI 50 D 4.5 B 0.5 achieves complete decoupling of T g (250.4 °C), bandgap (4.229 eV), and dielectric constant (4.01), while exhibiting outstanding high-temperature energy storage performance. At 150 °C and an electric field strength of 600 MV/m, it delivers an energy storage density of 6.5 J/cm 3 with an efficiency of 90 %. The performance not only surpasses that of the pure polymer PNI but also demonstrates strong competitiveness among reported polymer composites.