Attractive forces in sterically stabilized colloidal suspensions: From the effective potential to the phase diagram

Abstract

The potential of mean force for macroparticles at infinite dilution is computed for several models of solvent-solvent and solvent-macroparticle interactions by using the reference hypernetted chain (RHNC) integral equations with Rosenfeld's density functional theory bridge functions. The phase diagram of the associated effective fluid is obtained from the RHNC free energy for the fluid branch and the perturbation theory for the solid one. The computation of the effective potential and of the fluid branch is tested by comparison with Monte Carlo simulation. The important modifications with respect to the pure hard spheres that were previously reported are confirmed. The possibility of inverting the relative stability of the fluid-fluid and the fluid-solid transitions by appropriate combination of the interaction parameters is shown. The importance of a fine description of the interactions is illustrated in the example of the role of the range of the solvent-solvent interaction potential.

When mixtures of hard-sphere-like colloids do not behave as mixtures of hard spheres

“…The accuracy of this method has been positively checked against the simulation data of Refs. [17,23] for situations typical of solvent-colloid mixtures. We performed a similar test with interaction parameters corresponding to the pseudobinary mixtures considered in the literature as "HS-like."…”

“…[15,17]: for the fluid phase, the very accurate RHNC integral equations [24] were used with the bridge function of Malijevski and Labik [25] as unique input (see Ref. [26] for details).…”

“…First, it is generally difficult to anticipate in this case the complex interplay of non-HS contributions (see Refs. [14][15][16][17] for a discussion of true molecular solvent/colloid binary mixtures). Second, the fundamental features of the phase diagram of pure HS mixtures are critically dependent on the specific characteristics of the HS depletion well.…”

Multicomponent adhesive hard sphere models and short-ranged attractive interactions in colloidal or micellar solutions

“…In general, the indirect, solvent-mediated, solute-solute interactions depend on both the solute-solvent and solvent-solvent ones, and thus may be very difficult to evaluate [6,7,20,28,29]. We will now report several very simplified cases.…”

“…Several other studies of depletion forces, which go beyond the entropic HS approach by taking into account more refined representions of the solute-solvent and solvent-solvent interactions, are also available in the recent literature [6,7,20,28,29].…”