Role of water structure in the interpretation of colloid stability

Some studies of the stability of model colloidal systems have shown marked deviations from the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. These deviations have been interpreted in terms of structuring of the water next to the particles. To test this postulate it was decided to establish whether the fastest flocculation rates of a model system in the form of monodisperse polyvinylacetate sols were solely diffusion controlled as predicted by classical Smoluchowski theory. The flocculation rates of these sols in the presence of excess electrolyte were measured as a function of temperature using light-scattering methods and a Coulter counter. The experimental rates were lower than those predicted by the theory tending to confirm the initial postulate. Further evidence of this phenomenon has been gained from a study of relaxation times of the water in the system, as a function of temperature and particle concentration, using spin echo n.m.r. techniques.