Strategies for optimizing interfacial thermal resistance of thermally conductive hexagonal boron nitride/polymer composites: A review

Abstract With the continuous development of high‐end electronic information technologies such as 5G communications, thermal management is an urgent issue in the electronic and circuit industries due to the miniaturization, functionalization and integration. Recently, polymer‐based composites with the fillers of hexagonal boron nitride (h‐BN) have been regarded as promising candidates resulting from their excellent thermal conductivity (TC), good insulation and remarkable comprehensive properties. However, the high surface inertness of h‐BN itself, incompatibility with matrix and other fillers and mismatch of phonon‐spectrum will bring about the matrix/filler and filler/filler interfacial thermal resistance (ITR), which will greatly decline the TC of the composites, and limit their thermal management ability. Therefore, how to design, regulate and improve the interfacial states in composites and eventually enhance the TC is a current challenge. Researchers have made great effort to reduce the ITR of the composites to improve their TC. However, a comprehensive summary and analysis of researches on the improvement methods of the interface states in composites in the past 3 years is still lacking. In this work, the commonly used mechanism models, and simulation methods for calculating and predicting TC was summarized. From perspectives of Synthesis of h‐BNNs, modification, orientation, bridging and three‐dimensional structures construction, we reviewed strategies for improving the interface states in composites, and focused on the ITR regulation and TC improvement. The improvement effects of various methods on TC were compared. The development trend of high TC composite materials was prospected. Highlights Crystallinity, defect, size, flatness, thickness of hexagonal boron nitride nanosheets (BNNSs) affect interfacial thermal resistance (ITR). Nature of interaction between adjacent layers of BNNS need exploited. Interface and defect are root cause of extra phonon scattering. Shape, density, surface area, distribution and compatibility reduce ITR. Theory, model, simulation methods need developed on different levels.