Boosting mechanical and insulating properties of PMIA films via interfacial supramolecular interactions and charge traps

Abstract

Poly (m-phenylene isophthalamide) (PMIA), renowned for its excellent thermal stability, insulating properties, and mechanical modulus, is an ideal candidate for insulation encapsulation in electrical and electronic devices. Nevertheless, the inherent conjugated structure facilitates charge transport at elevated temperatures, leading to a drastic increase in leakage current and posing the risk of breakdown failure. Herein, we report an interface engineering strategy for PMIA films to realize synergistic enhancement of mechanical and insulation properties by decoupling their trade-off. 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) is incorporated to construct a dual-functional interface. The supramolecular interactions at the PMIA/NTCDA interface promote a conformational evolution toward short-range order, substantially enhancing structural stability. Meanwhile, the interfacial charge traps arising from energy level alignment facilitate charge entrapping and immobilization, thereby reducing leakage current and improving breakdown strength. At an optimal doping concentration of 0.3 wt%, the composite film achieves breakdown strengths of 523.8 MV·m−1 and 496.5 MV·m−1 at 150 °C and 200 °C, respectively, corresponding to increases of 49.6% and 62.6% compared to pristine PMIA. Moreover, the composite film exhibits a Young’s modulus of 4.15 GPa and a tensile strength of 152.7 MPa, outperforming typical polymer-based films. This work offers a new perspective for designing high-performance polymers by overcoming the trade-off between insulation and mechanical properties.