Aggregation in sulfate latex suspensions: The role of charge for stability predictions

Abstract

It is commonly reported that the classical aggregation theory by Derjaguin, Landau, Verwey and Overbeek (DLVO) fails to predict quantitatively the dependence of colloid stability on the electrolyte concentration of the solution and on the particle size. A connection of such problems to the typical surface charge density of model particles was indicated by a recent study of pH-dependent aggregation. The present investigation compares the mobility and aggregation behavior of differently charged sulfate latex particles, measured by electrophoresis and dynamic light scattering. We find a much closer agreement of observed and predicted stability for particles of very low surface charge. A new picture of the limitations of DLVO-theory follows from the analysis of theoretical energy profiles when combined with results from direct force measurements, and is strongly supported by our present findings.