Discontinuous change from thermally- to geometrically- dominated effective interactions in colloidal solutions

TL;DR

This study investigates how the effective interaction between colloids changes abruptly from being dominated by thermal fluctuations to geometric factors, depending on the nature of the cosolute clusters, revealing a discontinuous transition.

Contribution

It demonstrates that the effective potential range is governed by thermal correlation length in reversible clusters, contrasting with irreversible cluster behavior, and highlights the non-continuous nature of this transition.

Findings

Effective potential range depends on thermal correlation length.

Discontinuous change from thermal to geometric dominance.

Irreversible cluster case is a singular limit.

Abstract

We report numerical results for the effective potential arising between two colloids immersed in a self-assembling cosolute which forms reversible clusters. The potential is evaluated at cosolute state points with different densities and temperatures but with the same connectivity properties. We find that the range of the resulting effective potential is controlled only by the cosolute thermal correlation length rather than by its connectivity length. We discuss the significant differences with previous results focused on cosolute forming irreversible clusters and we show that irreversible bond case represents a singular limit which cannot be accessed in equilibrium by continuously increasing the bond lifetime.