STRUCTURES AND PHASE-TRANSITIONS IN COLLOIDAL DISPERSIONS FROM THEORY AND SIMULATION

Equilibrium properties of uncharged colloidal dispersions with particles interacting via harsh short-ranged repulsive forces and strong short-ranged attractive forces are determined by means of an approach in which colloids are treated as supramolecular versions of simple fluids. The interparticle interactions are represented by short-ranged square-well potentials. Structure factors and phase diagrams for the dispersions are determined analytically by mapping the square-well potential onto the adhesive-hard-sphere model by equating the respective second virial coefficients. Theoretical predictions are compared with molecular simulation results for the conditions relevant to real colloidal dispersions. Our results show that the adhesive-hard-sphere model can describe accurately structure factors and phase diagrams of nonionic microemulsions and inverted micellar systems containing AOT surfactant dispersed in oil. Both upper-critical and lower-critical consolute points in colloidal dispersions dominated by short-ranged attractive forces can be described using the same formalism.