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.