Effect of Polymer Chain Rearrangement in the Interfacial Area Caused by Chemical Bonding on Thermal Diffusion

There is a strong demand for polymers with high thermal conductivity; however, traditional composite fabrication methods frequently fall short of achieving the desired performance, primarily due to limitations at the polymer–filler interface. In this work, we experimentally demonstrate that molecular chain rearrangement in the interfacial region originates from chemical bonding between nanoparticles and the surrounding polymer matrix, which plays a crucial role in thermal transport. To examine this effect, we prepared boron nitride (BN)/polyimide (PI) composites in situ using fillers of unmodified BN as well as BN grafted with amino, carboxyl and hydroxyl groups. The thermal diffusivity of these composites was systematically evaluated, and the results show that chemical bonding promotes both improved phonon transport and optimised polymer chain distribution, leading to a peak in thermal diffusivity at moderate filler contents. This study highlights the essential role of interfacial chemical bonding and chain rearrangement in determining the thermal properties of polymer composites and provides useful guidance for designing materials with enhanced thermal conductivity.