Strong Coupling Electrostatics in the Presence of Dielectric Inhomogeneities

TL;DR

This paper investigates how dielectric inhomogeneities affect electrostatic interactions between charged membranes in the strong-coupling regime, revealing that dielectric mismatch can switch membrane interactions from attraction to repulsion.

Contribution

It extends strong-coupling theory to account for dielectric discontinuities and validates findings with Monte Carlo simulations, highlighting the impact on membrane interactions.

Findings

Dielectric mismatch causes counterion crowding in the membrane gap.

Membrane interactions switch from attractive to repulsive with increased dielectric mismatch.

Theoretical predictions align with simulation results at high coupling and mismatch.

Abstract

We study the strong-coupling (SC) interaction between two like-charged membranes of finite thickness embedded in a medium of higher dielectric constant. A generalized SC theory is applied along with extensive Monte-Carlo simulations to study the image charge effects induced by multiple dielectric discontinuities in this system. These effects lead to strong counterion crowding in the central region of the inter-surface space upon increasing the solvent/membrane dielectric mismatch and change the membrane interactions from attractive to repulsive at small separations. These features agree quantitatively with the SC theory at elevated couplings or dielectric mismatch where the correlation hole around counterions is larger than the thickness of the central counterion layer.