CH4在PVDF中渗透行为及机理的分子模拟研究

采用巨正则蒙特卡洛法（GCMC）和分子动力学法（MD）相结合的方法模拟研究了典型气体CH₄在聚偏氟乙烯（PVDF）中的吸附扩散行为，探讨了温度及压力对气体吸附扩散能力的影响，分析了CH₄在PVDF中的吸附位点及扩散轨迹。模拟结果表明，CH₄在PVDF中的溶解系数、渗透系数随温度的升高先增大后减小，随压力的升高而增大；扩散系数和自由体积分数均随温度和压力的升高而增大；吸附过程中，CH₄在PVDF内呈现有选择性地聚集吸附，且多吸附于模拟晶胞中的低势能区；随后，PVDF内的CH₄分子在以空穴形式存在的自由体积之间进行扩散，温度越高、压力越大，扩散能力越强。

Molecular Simulation of Permeation Behavior and Mechanism of CH_( 4) in PVDF

The adsorption and diffusion behavior of CH₄ in poly(vinylidene fluoride)(PVDF)was studied by a combination of molecular dynamics(MD)and Grand Canonical Monte Carlo(GCMC)simulations.The effects of temperature and pressure on the adsorption and diffusion capabilities of CH₄ were discussed,and the adsorption sites and diffusion paths of CH₄ in PVDF were analyzed.It was found that the solubility coefficient and permeability coefficient of CH₄ in PVDF increased at first and then tended to decrease with an increase in temperature.However,these two parameters always increased with an increase in pressure.As the temperature and pressure increased,the diffusion coefficient and fractional free volume increased.The simulated results indicated that the CH₄ molecules exhibited a selectively aggregated adsorption in PVDF,and they were mostly absorbed in the low potential region of the simulated cell.The CH₄ molecules in PVDF diffused within the free volumes in the form of cavities.The higher temperature and greater pressure can result in a better diffusion capability.