Design of Intrinsic Polyimides via a Restricted Dihedral‐Rotation Structural Strategy for Superior High‐Temperature Capacitive Applications

ABSTRACT With the advancement of high‐temperature electrical insulation technology, the limited energy‐storage capacity of the intrinsic polyimide (PI) matrix severely restricts application in harsh environments. This limitation primarily stems from their intrinsic structures, which hinder the coordinated optimization of suppressed charge‐transfer complexes (CTC), high glass‐transition temperature ( T g ), and dielectric constant ( ε r ). In this work, intrinsic PI dielectrics with restricted dihedral‐rotation structure were successfully constructed by employing ─Cl, ─CH 3 , and ─CF 3 . Such a structure effectively regulates molecular chain rigidity, thereby maintaining a high T g while preventing film failure induced by excessive internal stress. Additionally, highly electronegative substituents, together with restricted dihedral‐rotation structure, synergistically suppress CTC, thereby further enhancing breakdown strength ( E b ). Notably, ─Cl substituent compensates for the reduction in ε r resulting from CTC suppression, thereby enhancing the ε r and ultimately yielding outstanding discharged energy density ( U d ) of 11.47 J/cm 3 @150°C and 9.46 J/cm 3 @200°C. Furthermore, HBPDA/6FClTP exhibits outstanding power density and long‐term stability, with the fabricated high‐temperature‐resistant stacked‐film capacitor device showing excellent capacitance stability. This chemical modification strategy effectively achieves synergistic optimization of CTC suppression, T g , and ε r , thereby providing valuable guidance for the development of scalable, high‐performance polymer capacitors.