Phase-transition phenomena in colloidal systems with attractive and repulsive particle interactions

Abstract

We discuss certain aspects of phase transitions in colloidal systems with attractive or repulsive particle interactions. The colloidal systems studied are dispersions of spherical particles consisting of an amorphous silica core, coated with a variety of stabilizing layers, in organic solvents. The interaction may be varied from (steeply) repulsive to (deeply) attractive, by an appropriate choice of the stabilizing coating, the temperature and the solvent. In systems with an attractive interaction potential, a separation into two liquid-like phases which differ in concentration is observed. The location of the spinodal associated with this demixing process is measured with pulse-induced critical light scattering. If the interaction potential is repulsive, crystallization is observed. The rate of formation of crystallites as a function of the concentration of the colloidal particles is studied by means of time-resolved light scattering.