Unravelling Nanoconfined Films of Ionic Liquids

TL;DR

This paper presents an exactly solvable 1D Coulomb gas model to understand how ionic liquids behave under nanoconfinement, emphasizing the roles of key parameters and thermodynamic fluctuations in disjoining pressure.

Contribution

It introduces a novel analytical model that captures the effects of confinement and fluctuations on ionic liquids, aligning well with experimental observations without fitting parameters.

Findings

Disjoining pressure depends on two key dimensionless parameters.

Thermodynamic fluctuations are crucial in charged layer dynamics.

Model agrees qualitatively with experimental data.

Abstract

The confinement of an ionic liquid between charged solid surfaces is treated using an exactly solvable 1D Coulomb gas model. The theory highlights the importance of two dimensionless parameters: the fugacity of the ionic liquid, and the electrostatic interaction energy of ions at closest approach relative to thermal energy, in determining how the disjoining pressure exerted on the walls depends on the geometrical confinement. Our theory reveals that thermodynamic fluctuations play a vital role in the "squeezing out" of charged layers as the confinement is increased. The model shows good qualitative agreement with previous experimental data, with all parameters independently estimated without fitting.