Highly Thermally Conductive Polymer Composite Originated from Assembly of Boron Nitride at an Oil-Water Interface

Thermally conductive polymer packaging material is of great significance for the thermal management of electronics. Inorganic thermally conductive fillers have been demonstrated as a convenient approach to achieve this goal by sacrificing the lightweight and processability of the polymer. To address this problem, an effective 3D boron nitride (BN) network was constructed as a heat conduction pathway in a polystyrene (PS) matrix based on an oil-water interface assembly in this work. Styrene oil droplets were stabilized by BN sheets in the water phase to form Pickering emulsions, and then in situ polymerization was trigged to synthesize PS microspheres with ultrathin BN layer-covered surfaces (PS@BN microspheres). Composite substrates were fabricated through hot-compressing the PS@BN microspheres to form BN networks based on the original microsphere template. Benefited from the network structure, the maximum thermal conductivity of the composite substrate reached 0.94 W/mK at 33.3 wt % BN, which is 626% folds of that of pure PS. It was also demonstrated that the storage modulus and thermal stability of the composite substrate were dramatically improved by the BN network. The reported composite substrate and its fabrication strategy are promising in the development of thermal management of electronics.