DLVO AND NON-DLVO SURFACE FORCES AND INTERACTIONS IN COLLOIDAL DISPERSIONS

Some aspects of DLVO and non-DLVO forces in colloidal systems are over viewed. The influence of long range interactions on some kinetic prope rties of dispersions, as Brownian diffusion, is discussed. It is shown , both theoretically and experimentally, that the electrostatic repuls ion increases the collective diffusivity. The film stratification and oscillatory structure forces in colloidal suspensions are considered w ithin the framework of an uniform approach. The presence of small coll oidal species (e. g. micelles or polymer molecules) may lead to severa l maxima and minima in the disjoining pressure isotherm. The particula r case of interacting emulsion droplets is examined accounting for the interfacial deformability. The droplet deformation acts as a soft rep ulsion but affects also the remaining contributions ro the interaction energy due to changes of the droplet shape. A general procedure for c alculating the interdroplet interaction energy, as well as the equilib rium film radius and thickness in a doublet of droplets, is suggested. The energy of interaction between charged colloidal particles, due to correlations of the density fluctuations in the electric double layer is also studied. It is found that this effect may lead to attraction greater than the van der Waals contribution, especially when multivale nt counter ions are present.