Repeptization Determined by Turbidity and Photon Correlation Spectroscopy Measurements: Particle Size Effects

The aggregation of four polystyrene latexes with similar surface charge and different diameter has been examined by small angle light scattering. The DLVO model including aggregation at the secondary minimum qualitatively agrees with the experimental dependence of colloidal stability on particle size. Repeptization experiments, where the flocs were redispersed by washing away the coagulating salt, were carried out using two different methods: dialysis-turbidity and dilution-photon correlation spectroscopy. It was found that for the larger latexes the aggregates fragment after dilution, while for the smaller latexes the aggregates do not fragment. These results correlate closely with the hypothesis that particles may be captured within the secondary minimum of the theoretical interaction energy curves. Copyright 1997 Academic Press. Copyright 1997Academic Press