THEORIES OF PHASE BEHAVIOR OF COLLOIDAL SUSPENSIONS

Abstract

Colloidal suspensions are ubiquitous in nature. They also occur in many processes of industrial and technological interest. However, an understanding of the basic microscopic interactions and the rich phase behavior exhibited by colloidal suspensions is still lacking. In the present paper we give a short overview of the different statistical-mechanical approaches that have been proposed to account for the phase behavior and phase transitions occurring in systems made up of spherical colloidal particles immersed in a fluid matrix of structureless solvent particles. Effective interactions in these systems are seen to be invariably of a very short-ranged nature, and particular emphasis is put on different models that very accurately approximate these interactions. A central theme of this review is the effect of correctly incorporating the correlation structure of the colloidal system into the statistical-mechanical treatment, and how this feature very decisively affects the quality of the theoretical predictions for the colloid thermodynamics and phase behavior. Based on the importance of the correlation structure, theories relying on perturbative expressions are seen to fail to a higher or lesser extent when applied to systems of particles interacting via short-ranged potentials, and a critical discussion is provided on different proposals to overcome these difficulties. In particular, a recently proposed self-consistent nonperturbative theory is reviewed, and some of its more recent applications are shown.