Colloidal stability of polymer colloids with variable surface charge

Colloidal stability of two latexes with variable charge surface groups has been studied at a range of pH. Experimental log W vs log[electrolyte] plots were fitted using the DLVO theory, and values for the diffuse potential, p si(d) and the Hamaker constant, A, were obtained. Reasonable tendency was f ound for the diffuse potential of both latexes, decreasing when the surface charge decreased. However, the Hamaker constant, which was expected to be constant over the range of pH covered, also showed a decreasing behavior wi th decreasing charge. Several theories for the electric repulsive potential have been used to try to explain this paradoxing trend, although none of t hem was successful. Finally, two explanations are proposed, one based on co lon adsorption and the other on the hairy layer model, although the first o ne seems to be the most probable on the basis of thermodynamics considerati ons. (C) 1999 Academic Press.