Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
Membranes (Basel). 2015 Mar 10;5(1):99-119. doi: 10.3390/membranes5010099.
We study the permeation dynamics of helium and carbon dioxide through an atomistically detailed model of a polymer of intrinsic microporosity, PIM-1, via non-equilibrium molecular dynamics (NEMD) simulations. This work presents the first explicit molecular modeling of gas permeation through a high free-volume polymer sample, and it demonstrates how permeability and solubility can be obtained coherently from a single simulation. Solubilities in particular can be obtained to a very high degree of confidence and within experimental inaccuracies. Furthermore, the simulations make it possible to obtain very specific information on the diffusion dynamics of penetrant molecules and yield detailed maps of gas occupancy, which are akin to a digital tomographic scan of the polymer network. In addition to determining permeability and solubility directly from NEMD simulations, the results shed light on the permeation mechanism of the penetrant gases, suggesting that the relative openness of the microporous topology promotes the anomalous diffusion of penetrant gases, which entails a deviation from the pore hopping mechanism usually observed in gas diffusion in polymers.
我们通过非平衡分子动力学（NEMD）模拟研究了氦气和二氧化碳通过本征微孔聚合物 PIM-1 的原子细节模型的渗透动力学。这项工作首次对高自由体积聚合物样品中的气体渗透进行了明确的分子模拟，证明了如何从单个模拟中一致地获得渗透性和溶解度。特别是溶解度可以获得非常高的置信度和在实验误差范围内。此外，模拟还使我们能够获得关于渗透分子扩散动力学的非常具体的信息，并提供类似于聚合物网络的数字断层扫描的气体占据详细图。除了直接从 NEMD 模拟中确定渗透性和溶解度外，结果还揭示了渗透气体的渗透机制，表明微孔拓扑的相对开放性促进了渗透气体的异常扩散，这需要偏离通常在聚合物中观察到的气体扩散的孔跳跃机制。
