FLOCCULATION OF DISPERSIONS BY PREFERENTIAL ADSORPTION OF SOLVENTS FROM POLYMER-SOLUTION

An attempt was made to account for the adverse effect of the preferential adsorption of solvents onto particles from polymer solution (negative adsorption of polymer) on the stability of a dispersion in terms of osmotic attraction. The change in the energy of osmotic attraction on collision of solvated particles in a solution of macromolecules was calculated as a function of an osmotic pressure of the media, the thickness of the solvation layers, and the size of solute molecules, based on the assumption that the adsorption is irreversible and the adsorbed layers are impenetrable. The result showed that the energy of osmotic attraction is of the same order of magnitude as that of the electrostatic repulsion, indicating that the flocculation caused by the negative adsorption of polymers is mainly due to the osmotic attraction. Copyright © 1979 John Wiley & Sons, Inc.