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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, and Marjolein Dijkstra
Phys. Rev. Lett. 114, 038301 – Published 21 January 2015
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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.

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  • Received 12 September 2014

DOI:https://doi.org/10.1103/PhysRevLett.114.038301

© 2015 American Physical Society

Authors & Affiliations

John R. Edison1, Nikos Tasios1, Simone Belli2, Robert Evans3, René van Roij2, and Marjolein Dijkstra1,*

  • 1Soft Condensed Matter, Utrecht University, Princetonplein 5, 3584 CC Utrecht, Netherlands
  • 2Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, Netherlands
  • 3H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom

  • *m.dijkstra1@uu.nl

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Issue

Vol. 114, Iss. 3 — 23 January 2015

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