Thermal Conductivity of Long Chain Polymer Liquids: Molecular Dynamics Study on Contribution of Inter- and Intramolecular Energy Transfer

In this paper, we discuss the molecular mechanisms which determine the thermal conductivity of long chain polymer liquids according to the results observed in molecular dynamics simulations. Linear chain n-alkane, which is a typical polymer molecule, was chosen as our target of studies and non-equilibrium molecular dynamics (NEMD) simulations of bulk liquid n-alkanes under a constant temperature gradient and heat flux inside the simulation system were performed. Saturated liquids of 6 different chain length n-alkanes at the same reduced temperature (0.7Tc) were studied and the contributions of inter- and intramolecular energy transfer, which have been defined as the components of heat flux by the authors' previous theoretical study, were observed. The results show that in n-alkane liquids, the contribution of intramolecular energy transfer to the total heat flux as compared with the contribution of intermolecular energy transfer at the same reduced temperature and saturated density increases as the molecular length increases. It is revealed that in long chain polymer liquids, thermal energy is mainly transferred in the space along firm intramolecular bonds.