拉伸对聚乙烯分子链导热性能影响的分子动力学模拟  

Effect of Stretching on the Thermal Conductivity of Single Polyethylene Chains by Molecular Dynamics Simulations

作　　者：林也平[1,2] 张梦赟[1,2] 高艳芳[1,2] 梅林玉[1,2] 付一政[1,2] 刘亚青[1,2] 

机构地区：[1]中北大学山西省高分子复合材料工程技术研究中心,太原030051 [2]中北大学材料科学与工程学院,太原030051

出　　处：《高分子学报》2014年第6期789-793,共5页Acta Polymerica Sinica

摘　　要：采用非平衡分子动力学(NEMD)方法模拟了沿主链方向被拉伸的PE分子链的热输运过程,研究了链长(L)和拉伸应变(ε)对其导热性能的影响,通过分析振动态密度(VDOS)与导热率的关系,进一步探讨了高分子链中热输运过程的微观机理.结果表明,随着L和ε的增大,PE分子链的导热率逐渐增大,且增加趋势逐渐变缓;VDOS图谱的高频峰反映原子的拉伸、弯曲振动等,其随ε的增大而减弱;低频峰与体系的热扩散有关,其随ε的增大先增强后减弱.Nonequlibrium molecular dynamics （NEMD） has been used to simulate the heat transport in single PE chains stretched along the main chain direction. The effects of chain length （L） and tensile strain （8） on thermal conductivity of single PE chains are investigated. Furthermore, the microscopic mechanism of heat transport in polymer chains is studied. The simulation results show that the thermal conductivity of PE increases with increasing L and ε, and the trend gets gently. This trend about L is understood to be a result of competition between ballistic phonon transport and diffusive phonon transport in a single polymer chain and limitation from the finite-size effects. The trend about ε is determined by the growing phonon mean free path and decreasing number density of atoms during drawing. The spectrum of vibrational density of states （VDOS） presents some high frequency peaks which represent different vibrations （stretching, bending, etc. ） in PE chains, and these high vibrations decrease with increasing ε. The low frequency peaks of spectrum of VDOS associated with low frequency modes of vibrations are strengthened at first and then weakened with increasing ε, known to be significant for thermal conduction due to their thermal diffusivity.

关 键 词：聚乙烯 链长 拉伸应变 非平衡分子动力学 导热率 振动态密度 

分 类 号：O632.12[理学—高分子化学]