Interaction of spherical colloidal particles with planar surfaces

Abstract

The rate of deposition of spherical polystyrene latex particles on smooth plastic films has been determined with the rotating disc technique. When the particles were negatively charged and the film positively charged, the deposition rate was closely in agreement with the Levich theory of diffusion-controlled transport to a rotating disc. With negative particles and negative films, high electrolyte concentrations were required to produce measurable deposition and the kinetics could not be accounted for by the appropriate modification of the Derjaguin-Landau-Verwey-Overbeek theory of colloid stability for sphere-plate interaction (including a treatment for diffusion of particles in a linear potential field). Furthermore, the anomalous deposition in this system was not proportional to time or to concentration of sol, although the sol itself was substantially unaffected by electrolyte under the conditions of the experiment. The evidence strongly suggests that—even with this seemingly ideal model for studying sphere-plate interaction—anomalous deposition occurred preferentially on to areas of locally favourable potential or geometry (or both). This phenomenon may prove to be important in practical deposition systems.