Exotic Electrostatics: Unusual Features of Electrostatic Interactions between Macroions

TL;DR

This paper reviews advanced concepts in electrostatic interactions between macroions, highlighting phenomena like non-monotonic forces and effects of surface charge disorder that challenge traditional views.

Contribution

It introduces the concept of dressed counterions and analyzes the impact of quenched surface charge disorder on macroion interactions.

Findings

Non-monotonic interactions between macroions due to mixed coupling regimes.

Surface charge disorder can induce unexpected attractive forces.

Dressed counterions lead to complex electrostatic behaviors.

Abstract

We present an overview of our understanding of electrostatic interactions between charged macromolecular surfaces mediated by mobile counter- and coions. The dichotomy between the weak and the strong coupling regimes is described in detail and the way they engender repulsive and attractive interactions between nominally equally charged macroions. We also introduce the concept of dressed counterions in the case of many-component Coulomb fluids that are partially weakly and partially strongly coupled to local electrostatic fields leading to non-monotonic interactions between equally charged macroions. The effect of quenched surface charge disorder on the counterion-mediated electrostatic interactions is analyzed within the same conceptual framework and shown to lead to unexpected and extraordinary electrostatic interactions between randomly charged surfaces with equal mean surface charge densities or even between effectively neutral macroion surfaces. As a result, these recent developments challenge some cherished notions of pop culture.