Simulation Study On The Influence Of Chain Configuration On Thermal Conductivity Of Polyethylene

In recent years,due to the miniaturization and functionalization of electronic devices,thermal management materials have received increasing attention.For thermal management materials that require light,soft,and insulation,thermally conductive polymers have the advantage that metals and ceramics cannot be replaced.Generally,the intrinsic thermal conductivity of polymer materials is low.However,the study found that the stretched polyethylene chain has ultra-high thermal conductivity.There is an important relationship between the conformational state of the molecular chain and the thermal conductivity.However,it is difficult for experimental techniques to study the microstructure of molecular chains.Computer simulation technology can construct molecular chains of different conformations,and can quantitatively analyze the influence of their microscopic states on physical properties.This article uses molecular dynamics methods to study the relationship between polyethylene chain motion,polyethylene crystallization and its thermal conductivity.At the same time,in order to expand the calculation scale,this paper also established CG potential field parameters suitable for calculating the thermal conductivity of polyethylene.First,this paper establishes a one-dimensional polyethylene model and studies the effects of different chain lengths,stretch ratios,main chain rigidity and temperature on the thermal conductivity of polyethylene chains.The results show that as the chain length continues to increase,the thermal conductivity will gradually increase.And as the stretching ratio increases,the polyethylene chain will gradually straighten and the thermal conductivity will increase.The rigidity of the main chain will also greatly affect the thermal conductivity of the chain.The stronger the rigidity of the main chain,the higher the thermal conductivity.Temperature will affect the severity of the vibration of the polyethylene chain.The higher the temperature,the stronger the vibration and the greater the phonon scattering,resulting in a decrease in thermal conductivity.Then,the crystallization model of polyethylene was established in this paper,and the effects of crystallinity,the angle between the unit cells and the interface between crystalline and amorphous regions on the thermal conductivity of crystalline polyethylene were studied.The results show that the crystallinity will affect the thermal conductivity of crystalline polyethylene.The higher the crystallinity,the greater the thermal conductivity.However,the angle between the unit cells is the most important factor affecting the thermal conductivity.The angle of the unit cells is parallel to the direction of thermal conduction,and crystalline polyethylene will have high thermal conductivity.And the interface between crystalline and amorphous regions will also affect the thermal conductivity of crystalline polyethylene.Finally,the molecular dynamics and Inverse Boltzmann methods were used to construct a CG potential field parameter that can calculate the thermal conductivity of polyethylene.The accuracy of the new potential field parameters was verified from the aspects of density,bond and angle distribution functions,radial distribution functions,and thermal conductivity.This established the basis for expanding the calculation scale and simplifying the model.In this paper,the relationship between the molecular chain conformation and thermal conductivity of polyethylene is systematically studied,and the influence of the crystalline state on thermal conductivity is analyzed.The established coarse-grained potential field helps to further study the thermal conductivity of large-sized polyethylene systems.