Thermal conductivity of straight-chain polytetrafluoroethylene: A molecular dynamics study

Abstract

The thermal conductivity of straightened polytetrafluoroethylene (PTFE) was calculated by performing reverse non-equilibrium molecular dynamics simulations (RNEMD). The heat conduction of chainlike PTFE affected by chain length, temperature, strain as well as multiple-chain interaction was investigated, respectively. The results showed that the increase of thermal conductivity of PTFE by straightening is effective. The bulk thermal conductivity of chainlike PTFE has been increased by three orders of magnitude compared with that of the amorphous PTFE. The size effect of single-chain PTFE is significant and the thermal conductivity tends to be stale with increasing chain length. And the decrease of temperature-dependent thermal conductivity fits into the trend inversely proportional to temperature (T−1). Furthermore, the thermal conductivity of PTFE under tensile stress increases firstly and then decreases, which also appears in other some of low dimensional materials. And the thermal conductivity of multiple-chain PTFEs will be less than that of single-chain PTFE due to van der Waals interaction. But the decrease is not obvious owing to the strong electronegativity of the fluorine atom which makes the attraction between the molecular chains much less than the repulsive force. In addition, the amorphous PTFE was also constructed and stress-dependent thermal conductivity was studied. The results showed that the increase of thermal conductivity of amorphous systems benefits from the formation of the crystal region and chainlike region. This work theoretically provides the data and insights of chain-like PTFE.