Electrostatic interactions in critical solvents

TL;DR

This paper explores how electrostatic forces in near-critical binary liquid mixtures with salt are affected by critical phenomena, revealing that critical Casimir effects dominate near the critical point.

Contribution

It demonstrates that ion-solvent coupling can reverse electrostatic forces and shows that critical Casimir effects remain universal despite salt presence.

Findings

Ion-solvent coupling can turn repulsive electrostatics into attractive forces.

Critical Casimir effect dominates near the critical point.

Salt does not alter the universal properties of the Casimir effect.

Abstract

The subtle interplay between critical phenomena and electrostatics is investigated by considering the effective force acting on two parallel walls confining a near-critical binary liquid mixture with added salt. The ion-solvent coupling can turn a non-critical repulsive electrostatic force into an attractive one upon approaching the critical point. However, the effective force is eventually dominated by the critical Casimir effect, the universal properties of which are not altered by the presence of salt. This observation allows a consistent interpretation of recent experimental data.