Critical casimir forces and colloidal phase transitions in a near-critical solvent: A simple model reveals a rich phase diagram

John R. Edison, Nikos Tasios, Simone Belli, Robert Evans, René Van Roij, Marjolein Dijkstra

Research output: Contribution to journalArticle (Academic Journal)

27 Citations (Scopus)

Abstract

From experimental studies, it is well known that colloidal particles suspended in a near-critical binary solvent exhibit interesting aggregation phenomena, often associated with colloidal phase transitions and assumed to be driven by long-ranged solvent-mediated (SM) interactions (critical Casimir forces), set by the (diverging) correlation length of the solvent. We present the first simulation and theoretical study of an explicit model of a ternary mixture that mimics this situation. Both the effective SM pair interactions and the full ternary phase diagram are determined for Brownian disks suspended in an explicit two-dimensional supercritical binary liquid mixture. Gas-liquid and fluid-solid transitions are observed in a region that extends well away from criticality of the solvent reservoir. We discuss to what extent an effective pair-potential description can account for the phase behavior we observe. Our study provides a fresh perspective on how proximity to the critical point of the solvent reservoir might influence colloidal self-assembly.

Original languageEnglish
Article number038301
JournalPhysical Review Letters
Volume114
Issue number3
DOIs
Publication statusPublished - 21 Jan 2015

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