Customizing Adaptive Thermoplastic Polyimide Interfaces in Bismaleimide/Boron Nitride Composites: A Synergistic Approach to Achieving Insulation and Cyclic Durability

ABSTRACT In‐wheel motors work in high heat flux and frequent thermal shock environments, resulting in insulation failure and thermal stress cracking. Therefore, there is an urgent need for composite materials with high thermal conductivity, insulation, and interface stability. Bismaleimide resin has excellent heat resistance, but its brittleness and low thermal conductivity limit its application. The traditional thermal conductive filler has poor dispersion and poor interface adhesion. In order to solve this problem, thermoplastic polyimide (TPI) was grafted onto hexagonal boron nitride by in situ polymerization to construct a flexible interface. The TPI segment promotes directional filler assembly and continuous thermal pathways through viscoelastic stress. In addition, the lowest unoccupied molecular orbital energy difference of 2.071 eV inhibits carrier migration. The results show that the thermal conductivity of the composites increases by 2.7 times (0.607 W·m ⁻¹ ·K ⁻¹ ), the interfacial thermal resistance decreases (3.28 × 10 ⁻⁷ m ² ·K/W), and the breakdown strength increases (38.1 kV/mm). After thermal cycling, the breakdown strength only decreased by 3.8%, and the interfacial microcracks were effectively suppressed. This work provides a new strategy for the development of reliable insulating materials for high power electronic devices and advanced thermal management systems.