Interactions of neutral semipermeable shells in asymmetric electrolyte solutions

TL;DR

This study investigates how neutral semi-permeable shells interact in electrolyte solutions, revealing that ionic permeation leads to charge separation, which influences the electrostatic interactions and stability of the shells.

Contribution

It introduces a theoretical analysis of neutral semi-permeable shells' interactions in asymmetric electrolytes, highlighting the effects of ion valency on attraction and repulsion.

Findings

Low valency electrolytes cause repulsive interactions stabilizing shells.

Polyvalent ions induce attractive forces leading to aggregation.

Charge separation inside shells affects disjoining pressure.

Abstract

We study the ionic equilibria and interactions of neutral semi-permeable spherical shells immersed in electrolyte solutions, including polyions. Although the shells are uncharged, only one type of ions of the electrolyte can permeate them, thus leading to a steric charge separation in the system. This gives rise to a charge accumulation inside the shell and a build up of concentration- dependent shell potential, which converts into a disjoining pressure between the neighboring shells. These are quantified by using the Poisson-Boltzmann and integral equations theory. In particular, we show that in case of low valency electrolytes, interactions between shells are repulsive and can be sufficiently strong to stabilize the shell dispersion. In contrast, the charge correlation effects in solutions of polyvalent ions result in attractions between the shells, with can lead to their aggregation.