The role of complex formation in the flocculation of negatively charged sols with anionic polyelectrolytes

Summary Flocculation of negatively charged colloids by anionic polyelectrolytes, resulting from the adsorption of polymers on the colloid surface and from bridging of polymer chains between solid particles, is only possible if an appropriate concentration of electrolyte is present in the solution. Complex formation in the immediate vicinity of the sol surface between the counter cation and the functional groups of the polyelectrolyte plays a major role in the attachment of anionic polyelectrolytes to negative hydrophobic sols.Stability constants for Cu(II) polyacrylate and for the Ca complexes of a polyacrylic acid, hydrolyzed polyacrylamide and polystyrene sulfonate have been determined, and the effect of solution variables upon flocculation of AgBr/Br^– sols by anionic polyelectrolytes have been investigated. Ca⁺² ions affect the adsorption of polystyrenesulfonate on a negatively polarized mercury surface, as reflected in measurements of the differential capacitance; the presence of complex bound functional groups apparently changes the structure and orientation ability of the adsorbed polymer.With 5 figures in 10 details and 2 tables