Phase behaviour of colloids suspended in a near-critical solvent: a mean-field approach

Abstract

Colloids suspended in a binary solvent may, under suitable thermodynamic conditions, experience a wide variety of solvent-mediated interactions that can lead to colloidal phase transitions and aggregation phenomena. We present a simple mean-field theory, based on free-volume arguments, that describes the phase behaviour of colloids suspended in a near-critical binary solvent. The theory predicts rich phase behaviour: we find colloidal gas, liquid and crystal phases, a colloidal gas–liquid critical line and a colloidal solid–solid critical line. We compare our results with those of our recent simulation study of the same model in two dimensions. Our simple theory accounts for the main features of the phase diagrams found in simulations and sheds new light on the origin of colloidal aggregation lines in near-critical solvents.

Acknowledgements

It is a great pleasure to contribute to this Special Issue in honour of Jean-Pierre Hansen. R. Evans first met Jean-Pierre in 1977 in Aleria, Corsica; we were both teaching at a NATO Summer School on liquids. Jean-Pierre's lectures on ‘correlation functions and their relationship with experiments’, delivered with his trademark gusto and clarity at a small chalkboard, made a lasting impression on all who attended. This included the escapee from the nearby penitentiary who quickly decided he should give himself up. Jean-Pierre's seminars, research articles, reviews and, in particular, his books have been a continuous source of inspiration for R. Evans and countless others in our field. M. Dijkstra and R. van Roij first met Jean-Pierre in the early 1990s during a three-month work visit (M. Dijkstra) to ‘his’ Laboratoire de Physique at the Ecole Normale Supérieure in Lyon, France, and later at a NATO school on phase transitions in complex fluids in Varenna, Italy. Jean-Pierre's immense knowledge on any aspect of liquids and soft matter has impressed us ever since. M. Dijkstra and R. van Roij still benefit from the excellent scientific guidance Jean-Pierre offered to us when we were young postdocs in Oxford (1995) and Lyon (1997), respectively. Jean-Pierre's handwritten manuscripts (without any erasements) and the unimaginably broad content of ‘The Book’ (which keeps revealing new details with every read), as well as his charming personality, his broad interest in architecture, paintings and politics, and the exquisite dinner parties in Trambly and Oxford, are but a few of the lasting impressions he made on us. We wish Jean-Pierre and Martine all the very best in the coming years.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

J.R. Edison and M. Dijkstra acknowledge financial support from a Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) VICI grant.