Molecularly Engineered Dual‐Crosslinked Polymer Dielectrics for 200 °C Capacitive Energy Storage

Polymer films offer advantages for capacitors, but high‐temperature operation requires new dielectric materials. This study develops a molecular engineering strategy for poly(amide‐ester‐imide) (PAEI). Skeleton customization via amide groups and ultra‐long chains enhances the dielectric constant (ε r ) through optimized dipole alignment. Simultaneously, electrostatic interactions between PAEI and the organic semiconductor [6,6]‐phenyl‐C61 butyric acid methyl ester (PC61BM) promote hydrogen bonding, constructing a robust crosslinked network. Leveraging PC61BM's unique high electron affinity, the composite exhibits strong electron‐trapping capability, significantly reducing high‐temperature conduction loss (achieving an ultralow conductivity of 4.97 × 10 −13 S cm −1 at 200 °C). This synergistic effect suppresses carrier mobility by constructing deep electron traps. The resulting nanocomposite demonstrates breakthrough performance: ultralow conductivity and exceptional energy storage characteristics ( U e is 5.16 J cm −3 with η is 90.7% at 200 °C). Multiscale validation‐integrating DFT calculations, MD simulations, phase‐field simulations, and experimental characterization‐confirms that the molecularly engineered crosslinked network suppresses leakage current by trapping charges and restricting chain segment motion under coupled thermal/electrical stress. This work establishes a robust molecular blueprint for extreme‐condition dielectrics, demonstrating how nanoscale interfacial engineering bridges molecular design to macroscopic high‐temperature capacitive performance. The strategy provides a new pathway for next‐generation energy storage materials operating in harsh environments.