Fabrication of h-BN nano-sheet composite and evaluation of microcosmic physical interfaces effect on thermal diffusion

Polymeric materials possessing high thermal conductivity are expected in many fields. The effective way considered, is the incorporation of fillers into the polymer matrix, which cannot approach the expectation. In this study, the main challenge for promotion of thermal conductivity of the polymer composite is experimentally proved to be coming from microcosmic physical interfaces between BN particles and their surrounding polymer matrix. To figure out how the physical interface affects on the thermal diffusion behavior of composites, the boron nitride (BN) @polyaniline (PANI) core-shell nano sheets (BN@PANI) with different shell thicknesses are fabricated employing in situ polymerization at first, and then thermally degrading PANI in the composite producing the microcosmic physical interfaces with different thicknesses between polyimide (PI) matrix and BN fillers. The thermal diffusion properties are then evaluated. The thermal diffusivity is further shown to be gradually decreasing with increasing thickness of microcosmic physical interfaces. The results provide a strong evidence for why the thermal conductivity of the composite is difficult to meet expectations, and have precisely explained why the microscale composite possesses higher thermal conductivity than nanoscale composite. This study clearly evidences the role of microcosmic physical interfaces on the thermal conductivity of composites, and provides a powerful hint for preparing composites with optimal thermal properties in future.