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arXiv 2005.12811cond-mat.soft
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复合电解质中两性离子膜的相互作用

Interactions between Zwitterionic Membranes in Complex Electrolytes

Sahin Buyukdagli, Rudolf Podgornik

摘要:

我们研究了两性离子膜在由一价和多价离子组成的混合电解质中的静电相互作用。我们表明,一价盐的存在是一个有限的静电力存在的膜上的必要条件。因此,源自表面偶极子的平均场膜压表现出非均匀的盐依赖性,其特征在于,在稀盐条件下增强,在中间盐浓度下降低。在添加多价阳离子的亚摩尔盐溶液中,这些阳离子与表面偶极子的相反电荷的单独的相互作用,使膜间的压力更排斥在低的膜分离距离和强烈的吸引力在中间距离,导致在一个不连续的类似电荷结合的过渡,然后由膜结合过渡。通过扩展我们的形式主义,占与大盐浓度相关的校正,我们表明,膜的高表面偶极子密度浸入摩尔盐溶液中可能会发生膜结合过渡,即使没有多价阳离子。因此,膜工程的表面极化力的调谐可以是一个有效的方式来调整偶极膜在浓盐溶液中的平衡配置。

英文摘要:

We investigate the electrostatic interactions of zwitterionic membranes immersed in mixed electrolytes composed of mono- and multivalent ions. We show that the presence of monovalent salt is a necessary condition for the existence of a finite electrostatic force on the membrane. As a result, the mean-field membrane pressure originating from the surface dipoles exhibits a non-uniform salt dependence, characterized by an enhancement for dilute salt conditions and a decrease at intermediate salt concentrations. Upon addition of multivalent cations to the submolar salt solution, the separate interactions of these cations with the opposite charges of the surface dipoles makes the intermembrane pressure more repulsive at low membrane separation distances and strongly attractive at intermediate distances, resulting in a discontinuous like-charge binding transition followed by the membrane binding transition. By extending our formalism to account for correlation corrections associated with large salt concentrations, we show that membranes of high surface dipole density immersed in molar salt solutions may undergo a membrane binding transition even without the multivalent cations. Hence, the tuning of the surface polarization forces by membrane engineering can be an efficient way to adjust the equilibrium configuration of dipolar membranes in concentrated salt solutions.

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