Effect of electrolytes on solution behaviour of water soluble macromolecules

Abstract

The action of particular electrolytes in altering the solution properties of non-ionic macro-molecules is well documented, although the origin of this effect is not clearly defined. In order to clarify this point, the heats of dilution of poly(vinyl pyrrolidone) in electrolytes that salt-in and salt-out were measured. These suggested that entropic factors were responsible for the salting-out effect of (NH₄)₂SO₄, a result that is compatible with negative adsorption of the ions from the polymer, caused by image forces. Viscosity data on highly hydrophilic polymers support this model.