Thermodynamic studies of micelles, microemulsions and emulsions

Abstract

In the last twenty years or so, systematic studies of thermodynamic properties of colloidal systems have been undertaken in our laboratory. The properties investigated went from free energies, to volumes and enthalpies, to heat capacities, compressibilities and expansibilities. The aim of such work was to generate precise data, especially in the transition zones, which could be fitted by quantitative models, in order to gain information on the various factors which affect the stability of these systems. The systems studied were binary and ternary micellar systems, mixed micellar systems, aqueous organic mixtures which tend to form microaggregates, microemulsions and emulsions. All these systems can be understood, and in many cases treated semi-quantitatively, through very simple concepts: changes in hydration of hydrophobic solutes and surfactants, hydrophobic interactions and association, changes in micellar equilibria induced by factors such as temperature, pressure and additives, etc. The present overview will briefly cover all these various aspects with special emphasis on some of our recent work on more complex systems such as emulsions.