用分子理论方法测量接枝纳米孔中的电渗流特性
Measuring the characteristics of electroosmotic flow in a polyelectrolyte grafted nanopore by molecular theory approach
摘要：
在本文中，我们提出了一个分子理论分析的离子和电位分布，电离度的聚乙烯（PE）刷，速度分布，体积流量，离子选择性，离子传导和平流的电渗流在聚酸（PA）/聚碱（PB）接枝纳米孔。生成的构象由旋转异构态模型用于执行的自由能功能的系统，包括从介电常数，电解质的pH值，接枝密度弱PE刷，离子分区和离子大小的变化所产生的玻恩能量的影响的最小化。然后，在考虑流体/壁面滑移的情况下，求解Navier-Stokes-Brinkman方程，得到速度场。此外，数值解的准确性进行检查，通过比较目前的离子电导率与现有的实验数据的纳米孔接枝与4PVP刷用作合成质子门控离子通道的结果。本方法的应用使我们能够描述的电渗流在PE接枝的纳米孔的电流体动力学特性的不同因素，包括电解质的pH值，本体盐浓度和PE刷的接枝密度。我们表明，感兴趣的量的依赖性基本上依赖于聚合物链的类型。例如，增加电解质的pH导致PA/PB刷中带电位点的程度增加/减少，并且PA/PB接枝纳米孔的离子选择性的大小随电解质的pH的变化存在最小/最大点。然而，对于两种类型的PA和PB接枝的纳米孔，离子传导和平流大致是本体盐浓度和PE层的低范围接枝密度的上升函数。
英文摘要：
In this paper, we present a molecular theory analysis of ions and potential distribution, degree of ionization of polyelectrolyte (PE) brushes, velocity profile, volumetric flow rate, ionic selectivity, ionic conduction and advection by electroosmotic flow in poly-acid (PA)/poly-base (PB) grafted nanopores. The generated conformations by the Rotational Isomeric State model are used in performing the minimization of the free energy functional of the system including the effects of the Born energy arising from the variation of permittivity, pH of the electrolyte, grafting density of weak PE brushes, ion partitioning and ionic size. Then, the velocity field is obtained in the process of solving the Navier-Stokes-Brinkman equation by considering the interfacial fluid/wall slippage. Also, the accuracy of the numerical solutions is examined by comparing the present results of ionic conductivity with the existing experimental data for a nanopore grafted with 4PVP brushes used as a synthetic proton-gated ion channel. The application of the present methodology enables us to describe the electrohydrodynamic characteristics of electroosmotic flow in PE grafted nanopores in terms of different factors including the pH of the electrolyte, bulk salt concentration and the grafting density of PE brushes. We show that the dependency of the quantities of interest are essentially rely on the type of the polymer chains. For instance, increasing the pH of the electrolyte results in an increase/decrease of the degree of charged sites in the PA/PB brushes, and there exists a minimum/maximum point in the variation of magnitude of the ion selectivity of PA/PB grafted nanopore with the pH of the electrolyte. However, for both types of PA and PB grafted nanopores, ionic conduction and advection are approximately the ascending function of the bulk salt concentration and low range grafting density of the PE layer.
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