A Two-Component Model for the Phase Behavior of Dispersions Containing Associative Polymer

A statistical mechanical theory is developed to predict the flocculation or phase separation of a colloidal dispersion by associating polymer. The system is modeled as a binary mixture of hard colloid spheres and Gaussian polymer chains with adhesive end groups or “stickers”. Interaction potentials are derived in terms of the sticker-sticker and sticker-colloid adhesion energies and the number of Gaussian segments in a coil. These pair potentials then determine equilibrium phase behavior via the Barker-Henderson perturbation theory. Phase diagrams illustrate the effects of polymer properties on the extent of fluid-fluid phase separation. in the weak sticker limit, volume restriction flocculation is predicted; however, increasing sticker-colloid adhesion stabilizes the system.