Effective interactions and phase behaviour for a model clay suspension in an electrolyte

TL;DR

This paper develops an improved model for the effective interactions between charged disc-like clay particles in electrolytes, incorporating charge renormalization and anisotropy, and explores their phase behavior through simulations.

Contribution

It introduces a novel pair potential for charged discs that includes non-linear effects and anisotropy, advancing the theoretical understanding of clay suspension phases.

Findings

Constructed a pair potential incorporating charge renormalization and anisotropy.

Discussed phase behavior of Laponite dispersions based on the new model.

Presented Monte Carlo simulation results on mesostructure.

Abstract

Since the early observation of nematic phases of disc-like clay colloids by Langmuir in 1938, the phase behaviour of such systems has resisted theoretical understanding. The main reason is that there is no satisfactory generalization for charged discs of the isotropic DLVO potential describing the effective interactions between a pair of spherical colloids in an electrolyte. In this contribution, we show how to construct such a pair potential, incorporating approximately both the non-linear effects of counter-ion condensation (charge renormalization) and the anisotropy of the charged platelets. The consequences on the phase behaviour of Laponite dispersions (thin discs of 30 nm diameter and 1 nm thickness) are discussed, and investigation into the mesostructure via Monte Carlo simulations are presented.