Chain Topology Engineering in Amphiphilic Block Copolymers: Crosslinking‐Induced Nanodomain Refinement for Ultrahigh Energy Density under Extreme Conditions

An amphiphilic block copolymer is constructed via self‐assembly‐induced nanoscale microphase separation. A crosslinker with dual electron‐withdrawing groups (─CF3/─O─) is introduced to refine the PEA phase domain. The crosslinking film achieves record‐high energy densities of 11.07 J cm−3 (150 °C/700 MV m−1) and 6.45 J cm−3 (200 °C/600 MV m−1) with an efficiency of >90%. Abstract The growing demand for high‐performance capacitors in extreme environments drives the development of polymer dielectrics with high energy capability and thermal stability. Here, an amphiphilic block copolymer constructed via self‐assembly‐induced nanoscale microphase separation is presented, in which fluorinated polyimide (FPI) and flexible polyetheramine (PEA) segments form thermally entropy‐driven domains. Density‐of‐state model reveals significant electronic heterogeneity of the resultant copolymer, in which FPI exhibits an energy gap of 3.49 eV while PEA demonstrates a wide gap of 7.31 eV, resulting in an interfacial offset of 5.28 eV that inherently restrains the migration of charge carriers. A trifunctional crosslinker with dual electron‐withdrawing groups (─CF3/─O─) is introduced to refine the PEA phase domain that decreases to 13.7 nm from an initial long period of 19.2 nm. The crosslinking system achieves record‐high energy densities of 11.07 J cm−3 (150 °C/700 MV m−1) and 6.45 J cm−3 (200 °C/600 MV m−1) with an efficiency of >90%, which is attributed to the diminished hopping distance of charge carriers under high‐temperature electric field. The received copolymer film retains 1.56 J cm−3 and an efficiency of 94% with fluctuation of <5% after 105 charge–discharge cycles at 200 °C and 300 MV m−1. By synergizing amphiphilic energy‐level engineering with entropy‐driven phase refinement, this strategy establishes a robust material platform for a high‐temperature capacitor, balancing ultrahigh energy storage and dielectric reliability. An amphiphilic block copolymer is constructed via self-assembly-induced nanoscale microphase separation. A crosslinker with dual electron-withdrawing groups (─CF 3 /─O─) is introduced to refine the PEA phase domain. The crosslinking film achieves record-high energy densities of 11.07 J cm −3 (150 °C/700 MV m −1 ) and 6.45 J cm −3 (200 °C/600 MV m −1 ) with an efficiency of >90%. Abstract The growing demand for high-performance capacitors in extreme environments drives the development of polymer dielectrics with high energy capability and thermal stability. Here, an amphiphilic block copolymer constructed via self-assembly-induced nanoscale microphase separation is presented, in which fluorinated polyimide (FPI) and flexible polyetheramine (PEA) segments form thermally entropy-driven domains. Density-of-state model reveals significant electronic heterogeneity of the resultant copolymer, in which FPI exhibits an energy gap of 3.49 eV while PEA demonstrates a wide gap of 7.31 eV, resulting in an interfacial offset of 5.28 eV that inherently restrains the migration of charge carriers. A trifunctional crosslinker with dual electron-withdrawing groups (─CF 3 /─O─) is introduced to refine the PEA phase domain that decreases to 13.7 nm from an initial long period of 19.2 nm. The crosslinking system achieves record-high energy densities of 11.07 J cm −3 (150 °C/700 MV m −1 ) and 6.45 J cm −3 (200 °C/600 MV m −1 ) with an efficiency of >90%, which is attributed to the diminished hopping distance of charge carriers under high-temperature electric field. The received copolymer film retains 1.56 J cm −3 and an efficiency of 94% with fluctuation of <5% after 10 5 charge–discharge cycles at 200 °C and 300 MV m −1. By synergizing amphiphilic energy-level engineering with entropy-driven phase refinement, this strategy establishes a robust material platform for a high-temperature capacitor, balancing ultrahigh energy storage and dielectric reliability. Advanced Science, Volume 12, Issue 42, November 13, 2025.