Molecular dynamics simulation of the thermal conductivity mechanism of polydimethylsiloxane composites filled by multilayer hexagonal boron nitride

To design polydimethylsiloxane (PDMS)-based nanocomposites with high thermal conductivity, multiscale simulations were adopted to study the effect of the modified hexagonal boron nitride (h-BN) and the layer number of h-BN on the interface improvement of nanocomposites. The results indicate that 6-aminocaproic acid (ACA) effectively improves the interfacial thermal conductivity of the composites. The interaction energy between h-BN modified by ACA (ACA@h-BN) and PDMS is enhanced compared to that of an unmodified h-BN/ PDMS composite system. It's interesting that the change rate of thermal conductivity (delta) delta ) decreases first and then increases with the increase in the layer number of ACA@h-BN, and gradually increases to a value more equal to that of the single-layer system when the layer number of ACA@h-BN reaches 5. The interfacial thickness increases from 1.93 & Aring; to 2.60 & Aring; as the layer number of ACA@h-BN increases from 1 to 6, which is beneficial to improve the thermal conductivity. However, the matching coefficient (M) M ) of the phonon vibration power spectrum between PDMS and ACA@h-BN decreases from 0.024 to 0.011 as the layer number of ACA@h-BN increases from 1 to 6, which impairs the thermal conductivity. The decrease in M dominates the delta in the composites filled by h-BN with 1-3 layers. The thermal conductivity is more affected by the specific gravity of ACA@h-BN than M in the composites filled by h-BN with 4-6 layers. It is proposed that the ideal single-layer ACA@h-BN can be replaced to some extent by the ACA@h-BN with 5 layers to improve the thermal properties of the composites. This work is expected to provide theoretical support for interface modification of nano- composites, and preparation of high-thermal conductivity composites.