物理化学学报 >> 2016, Vol. 32 >> Issue (10): 2523-2530.doi: 10.3866/PKU.WHXB201606292

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气体在无定型聚异戊二烯中扩散的分子动力学模拟

鲁相1,*(),陈循1,汪亚顺1,谭源源1,高木子源2   

  1. 1 国防科学技术大学机电工程与自动化学院,装备综合保障技术重点实验室,长沙410073
    2 阿尔伯塔大学化学与材料工程系,埃德蒙顿T6G0X6,加拿大
  • 收稿日期:2016-04-28 发布日期:2016-09-30
  • 通讯作者: 鲁相 E-mail:luxiang9014@126.com
  • 基金资助:
    国家自然科学基金资助项目(51375487,51205402)

Molecular Dynamics Simulation of Gas Transport in Amorphous Polyisoprene

Xiang LU1,*(),Xun CHEN1,Ya-Shun WANG1,Yuan-Yuan TAN1,Zi-Yuan GAOMU2   

  1. 1 Laboratory of Science and Technology on Integrated Logistics Support, College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha 410073, P. R. China
    2 Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G0X6, Canada
  • Received:2016-04-28 Published:2016-09-30
  • Contact: Xiang LU E-mail:luxiang9014@126.com
  • Supported by:
    The project was supported by the National Natural Science Foundation of China(51375487,51205402)

摘要:

采用分子动力学模拟方法研究了多个温度下氧气、氮气及甲烷在无定型顺式1,4-聚异戊二烯中的扩散系数。在模拟过程中,使用COMPASS力场作为分子力场。应用COMPASS力场的势能函数,聚合物的密度及玻璃化转变温度的计算结果与实验值有较好吻合。在278-378 K的温度范围内,通过3或1.5 ns时长的正则系综动力学模拟,计算了不同温度下氧气、氮气及甲烷的扩散系数。结果表明,根据爱因斯坦关系式计算得到的扩散系数与实验结果比较接近。对气体扩散系数与温度的关系进一步研究,发现在278-378 K温度范围内,甲烷的扩散系数随温度变化的半对数曲线图是非线性的,而氧气和氮气的扩散系数随温度变化的半对数曲线图是线性的。本文研究结果有助于理解温度对气体扩散的影响机制,并为高温下气体在天然橡胶中扩散系数的测定及天然橡胶热氧老化建模分析提供依据。

关键词: 气体, 扩散系数, 聚异戊二烯, 分子动力学, 分子模拟

Abstract:

Molecular dynamics (MD) simulations were performed to study the transport properties of gases (oxygen, nitrogen, and methane) in amorphous cis-1,4-polyisoprene over a wide range of temperatures. The COMPASS force field was used as the molecular mechanics force field in the simulations. Experimental values of density and glass transition temperature were successfully reproduced using the atomistic potentials determined by COMPASS. Diffusion coefficients were determined from long NVT simulation times (up to 3 or 1.5 ns) in the temperature range of 278-378 K. The diffusion coefficients calculated fromthe Einstein relationship agree well with available experimental data. Further studies on the temperature dependence of diffusion coefficients indicate that curvature is observed in the Arrhenius plot of diffusivity versus inverse temperature for methane, but the plots are linear over the investigated temperature range for oxygen and nitrogen. These simulation results are useful to understand the temperature dependence of diffusion coefficients, and provide a basis for the determination of diffusion coefficients at high temperatures and the modeling of thermo-oxidative degradation of polyisoprene.

Key words: Gas, Diffusion coefficient, Polyisoprene, Molecular dynamics, Molecular simulation

MSC2000: 

  • O641