Segmental-Incompatibility-Enabled Non-Conjugated Nanodomains for Aggregation-State Regulation of Wide-Temperature Polyimide Energy-Storage Dielectrics

Addressing the issues of accelerated charge migration and diminished energy storage performance in polyimide (PI) under a high-temperature electric field, this study proposes an aggregation-state regulation strategy through the construction of non-conjugated nanodomains in PI-based copolymers. By introducing non-conjugated polydimethylsiloxane (PDMS) diamine into the PI backbone and leveraging the segmental incompatibility between aromatic PI and PDMS segments, a nanoscale “sea-island” phase-separated structure is generated based on the enthalpy-driven phase separation principle. This tailored heterogeneous structure weakens compact aromatic packing, reduces local electronic coupling between PI-derived segments, and suppresses long-range charge migration while simultaneously introducing deep trapping sites at heterogeneous interfaces, thereby synergistically regulating charge diffusion behavior of the PI-PDMS copolymer. The resultant PI-PDMS film exhibits outstanding performance over a wide-temperature range: a dielectric constant of 4.41 with low loss of <0.015 at 100 Hz, a discharged energy density of 16.2 J/cm 3 with efficiency of > 90% at 950 MV/m and 25°C, and 6.6 J/cm 3 with efficiency of > 90% at 600 MV/m and 200°C. This research establishes a fresh paradigm for the design of high-performance polymer dielectrics through aggregation-state regulation.