Interface Heat Conductance Performance Of Graphene/polymer: A Molecular Dynamics Simulation

In recent years, the rapid development of electronic information industry provides thermal conductive polymer materials with larger development space, and continuously puts forward new requirements to the performance of thermal conductance. Interfacial thermal resistance is considered to be the main factor limiting the further improvement of thermal conductivity of filled polymer materials. Therefore, improving the interface thermal conductance and exploring the micro thermal conduction mechanism has become the key to further improve the thermal conductivity of polymer materials. The non-equilibrium molecular dynamics(NEMD) simulation is used to study the effect of the graphene filler size, number of layers and functions(-H、-OH)and polymer density, side group on the performance of interface thermal conductance of graphene/polymer composites, The effective medium theory(EMT) was used to link the thermal conductivity of the composite with the overall thermal conductivity of the composites. The influence of the interface thermal conductance, the length of the filler and the volume fraction of the filler on the thermal conductivity of composite was predicted. And further to explore the microstructure of interface thermal conduction mechanism, in order to improve polymer composites interface thermal conductance and to provide theoretical prediction and guidance.The results shows that interface thermal conductance increases with the increase of the size and functionalization degree of graphene. This is because that with the increase of graphene size, the long wavelength phonons is excited and promote the heat transfer at the interface. VPS analysis find new vibration modes appeared in lower frequency domain(<2THz) and produced a greater degree of coupling vibration with vibration modes of polymer carbon atom, then increased the interfacial heat transfer capability. With the increase of the degree of functionalization, the result of VPS shows that graphene carbon atom vibration mode produced rearrangement and caused greater area of overlap with the vibration of carbon atoms of polymer, and the out-of-plane vibration of graphene carbon atoms play main roles in interfacial heat transfer. In the same degree, the interface thermal conductance value of-OH functionalized graphene system is greater than that of H atoms functionalized graphene system. When the flow is perpendicular to the graphene plane, interface thermal conductance firstly decrease with the increase of the number of layers and then tends to be stable. Heat flow parallels to the graphene plane, interface thermal conductance increases with the increase of the number of layers. VPS shows that the out-of-plane vibration of graphene atoms rearranges obviously with the increase of the number of layers and plays a leading role in the process of interfacial heat transfer.The effects of polymer density and different side groups(-CH3,-OH,-Cl) on the thermal conductance of the interface were syudied. It is found that interface thermal conductance increases with the increase of the polymer density. The RDF between carbon atoms of graphene and carbon atoms of polymer increases with the increase of the density. VPS shows that the vibration mode of polymer carbon atoms shifts to the higher frequency domain with the increase of the density and produces larger area of overlap with the vibration mode of graphene carbon atom. The presence of side group can cause internal rotation of the molecule chain to be blocked, leads to a decrease in mean square displacement(MSD) of the polymer chain, then the movement ability of the molecular chain is decreased. VPS results shows that the polar groups promote the transfer of heat flux at the interface to a certain extent.