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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.
The heat transport process of PE molecular chains stretched in the main chain direction was simulated by the non-equilibrium molecular dynamics (NEMD) method. The influence of chain length (L) and tensile strain (ε) on the thermal conductivity of PE was studied. The microscopic mechanism of heat transport in polymer chains was further investigated by analyzing the relationship between the density of states (VDOS) and the thermal conductivity. The results show that the thermal conductivity of PE chains gradually increases with the increase of L and ε , And the increasing trend gradually becomes slower. The high-frequency peak of VDOS spectrum reflects the tensile and flexural vibration of atoms, which decreases with the increase of ε. The low-frequency peak is related to the thermal diffusion of the system, which increases and then decreases with the increase of ε .