Exceptional high-temperature capacitive performance of PEI dielectric films via intermolecular forces from trifluoromethyl and hydroxyl

Aromatic polymers, such as polyetherimide (PEI), have attracted significant attention as potential dielectrics for energy storage in high-temperature-resistant film capacitors. However, the conjugated structure of these polymers facilitates electric charge transport, leading to an exponential increase in conduction loss and a dramatic deterioration in energy storage performance at elevated temperatures and high electric fields. In this study, we propose modulating the molecular chain conformation and intermolecular forces synergistically to significantly enhance the high-temperature capacitance performance of PEI-based dielectric films. Copolymerizing the amide group 6FAP (2,2-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane) into the PEI backbone, constructing a strong intermolecular hydrogen network, which suppresses the π-π conjugation effect and ameliorates the negative effects in increased the free volume. Experimental findings suggest that intermolecular hydrogen bonds can elevate the energy level of deep traps, impeding carrier migration and enhancing the capture process. Meanwhile, the spatial hindrance and electron-induced effects of trifluoromethyl (-CF 3 ) enhance dipole-oriented polarization. Consequently, a synergistic enhancement in breakdown field strength and dielectric constant is observed in PEI-6FAP films, accompanied by discharge energy density of 5.93 J/cm 3 (efficiency>90 %) at 150 °C. This work provides a prospective paradigm for modulating the molecular structure of PEI films and further validates the promising application of PEI dielectric film capacitors in elevated temperature conditions.