Macromolecular surface phases and the stability of colloidal dispersions

Abstract

The effect of adsorbing a flexible polymer onto the surface of a system of colloidal particles in dispersion is considered from the point of view of polymer solution theory. The analogy between the free energy of mixing of polymer and solvent and colloid and solvent is stressed and the appropriate interaction parameters are defined. It is shown that the stabilizing effect of polymer adsorption (“steric” stabilization) on the free energy of mixing of the entire system is mainly due to a reduction (by adsorption) of the polymer concentration in the bulk solution. “Steric” stabilization is only rarely the thermodynamically preferred effect. In many instances where it is effective it is due to the persistence of a metastable condition.