Molecular dynamics simulation of diffusion behavior of benzene/water in PDMS-calix[4]arene hybrid pervaporation membranes
Molecular dynamics simulation of diffusion behavior of benzene/water in PDMS-calix[4]arene hybrid pervaporation membranes
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DOI：
10.1021/ie0708935
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发表时间：
2008-07-02
影响因子：
4.2
通讯作者：
Jiang, Zhongyi
中科院分区：
文献类型：
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作者：
Li, Ben;Pan, Fusheng;Jiang, Zhongyi
以含杯[4]芳烃(CA)的聚二甲基硅氧烷(PDMS)膜渗透汽化脱除稀溶液中的苯为模型体系，采用分子动力学(MD)模拟方法研究了小分子渗透剂在橡胶-聚合物杂化膜中的扩散行为。在我们之前的实验研究中，苯(NPRb)和分离因子(苯/水)通过PDMS-CA杂化膜的归一化渗透速率并不遵循通常的单调或单峰/谷变化，而是伴随着最小值和最大值。采用分子动力学模拟方法，对PDMS和CA在纯膜和杂化膜中的非键相互作用能、均方位移量、自由体积特性以及苯和水的扩散系数进行了分析。模拟结果表明，MSD和自由体积分数(FFV)值与相互作用能密切相关。苯和水在“无限稀释”和饱和状态下的扩散系数呈现相同的变化趋势，但饱和状态下的扩散系数略大。此外，还观察到扩散系数不仅与FFV有关，还受CA与渗透剂之间的相互作用的影响。总体而言，中间结果与实验结果吻合较好。
Molecular dynamics (MD) simulation was employed to investigate diffusion behavior of small penetrants in rubbery-polymer-based hybrid membranes, using pervaporative removal of benzene from its dilute solution by poly(dimethylsiloxane) (PDMS) membranes filled with calix[4]arene (CA) as the model system. In our previous experimental investigation, the normalized permeation rate of benzene (NPRb) and separation factor (benzene/water) through PDMS-CA hybrid membranes did not follow the usual monotonous or single peak/valley change, but accompanied minimum and maximum values instead. In the present study, nonbonding interaction energy between PDMS and CA, mean-square displacement (MSD), free volume characteristics, and diffusion coefficients of benzene and water in pure PDMS and hybrid membranes were analyzed by molecular dynamics simulation. The simulation results revealed that MSD and fractional free volume (FFV) values were closely dependent on interaction energy. Diffusion coefficients of benzene and water at "infinite dilution" and saturated condition displayed the same changing tendency, although the values at saturated condition were a bit larger. Moreover, it was observed that diffusion coefficients were not only related to FFV but also affected by the interaction between CA and the penetrants. Overall, the MID results agreed well with the experimental results.