Attractions in sterically stabilized silica dispersions : I. Theory of phase separation

Abstract

The presence of an attractive term in the interaction potential between colloidal particles will result in a phase separation (often a flocculation) on lowering the temperature. In this paper the attraction itself is assumed to increase on lowering the temperature in a manner similar to that observed in polymer solutions. A Van der Waals-like equation of state is introduced. For the osmotic pressure in this expression the Percus-Yevick (compressibility) relation is used. Phase diagrams are calculated by equating the thermodynamic potentials of solvent and colloidal particles in both phases. Both two and three component systems are dealt with. Polydispersity results in binodals which depend on initial concentration.