Theory of phase equilibria in polymer stabilized colloidal suspensions

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Abstract
The results of calculations describing the observed phase behaviour of polymer stabilized colloidal dispersions based on the Gibbs-Bogolyubov variational approach are presented. The effective pairwise additive macroparticle interaction is assumed to be a superposition of Yukawa potentials. Hardspheres are chosen as the reference system for the disordered phases, while an Einstein model is taken to be a suitable reference system for the ordered phases. In sterically stabilized colloidal dispersions, temperature variations in the range of the repulsive steric interaction between macroparticles are allowed. Additional insight into the temperature dependence of the adsorbed polymer layer thickness is obtained by comparing the results of the variational approach with those obtained using the phenomenological Flory-Huggins theory of phase separation. In order to describe the observed reversible depletion flocculation, the double Yukawa model potential permits changes in the depletion attraction with free polymer concentration.