Year: 2026
Type: preprint
Abstract: In most theories of electrolyte and polyelectrolyte solutions, the solvent is treated implicitly as a dielectric continuum. While this approximation has enabled major advances, it neglects coupling between ionic and dipolar degrees of freedom. Using molecular dynamics simulations and the mean-spherical approximation, we show that this coupling qualitatively alters electrostatically driven phase behaviour. At finite ion concentrations, many-body ion-dipole correlations reverse the temperature dependence of effective electrostatic interactions, leading to upper-critical solution temperature (UCST) behaviour in direct contrast to the lower-critical solution temperature (LCST) behaviour predicted by implicit-solvent electrostatic theories. This phase reversal arises from ion-induced suppression of local dipolar screening, a collective effect inaccessible to pairwise implicit-solvent descriptions.
Source: arXiv (Cornell University)
Authors: Walker, Pierre J., Wang, Zhen-Gang
Institution: California Institute of Technology
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221769428