Role of Molecular Polarity in Thermal Transport of Boron Nitride-Organic Molecule Composites

Understanding the role of fillers in the thermal transport of composite materials is of great importance to engineering better materials. The filler induces material interfaces within the composite, which influence the thermal transport between the matrix and themselves. The filler can also alter the molecular arrangement of the matrix in its vicinity, which may also impact the thermal transport ability. In this paper, molecular dynamics simulations are performed to study the thermal transport across the matrix-filler interfaces in hexagonal boron nitride (h-BN)-organic molecule composites. Four different organic molecules are studied as the matrixes. They include hexane (C₆H₁₄), hexanamine (C₆H₁₃NH₂), hexanol (C₆H₁₃OH), and hexanoic acid (C₅H₁₁COOH), which feature the same molecular backbone but increasingly different polar functional groups. The nominal local thermal conductivities of the hexane matrix with varying distances to the interface are calculated to demonstrate the influence of the filler on the thermal transport properties of the matrix. It is found that a more polar matrix exhibits a higher density in the near-interface region and a higher nominal local thermal conductivity, suggesting that the interfacial interaction can impact the local heat transfer ability of the matrix. In addition, the more polar matrix also leads to a larger interfacial thermal conductance with h-BN (hexane: 90.47 ± 14.49 MW/m² K, hexanamine: 113.38 ± 17.72 MW/m² K, hexanol: 136.16 ± 25.12 MW/m² K, and hexanoic acid: 155.17 ± 24.89 MW/m² K) because of the higher matrix density near the interface and thus more atoms exchanging energy with the filler. The results of this study may provide useful information for designing composite materials for heat transfer applications.