STABILITY DIAGRAMS FOR COLLOIDAL DISPERSIONS WITH ATTRACTIVE INTERACTIONS - AN ANALYTICAL APPROXIMATION

We show that a single-parameter, adhesive-hard-sphere (AHS) model can be used to estimate, analytically, the stability diagrams for colloidal dispersions interacting through fairly long-range attractive forces. The use of the model is illustrated for polymer-induced depletion interactions. Analytical expressions are given for the static structure factors, pressures and chemical potentials in terms of the adhesiveness parameter of the AHS model. The adhesiveness parameter is obtained as a function of the relevant parameters appropriate for the actual interaction forces using the second virial coefficient (which can be measured experimentally using scattering techniques). It is shown that both upper-critical and lower-critical stability domains can be predicted, in addition to static structure factors. The results presented are consistent with the predictions based on more elaborate statistical mechanical theories.