EVANESCENT WAVE SCATTERING STUDIES ON LATEX-GLASS INTERACTIONS

The intensity of light scattered by polystyrene latex particles was measured as a function of the penetration depth of the evanescent wave and compared to the predicted values based on the distribution of particles near the glass surface calculated from the appropriate DLVO theory. This was done for various electrolyte concentrations corresponding to the ratio of particle radius to double layer thickness in the range 0.34-9.7. The agreement between theory and experiment was excellent. A photon correlation spectroscopic optical constant b was also measured as a function of the penetration depth. For all but the highest electrolyte concentration used, b scaled with the scattered light intensity. The deviation at the highest salt concentration was tentatively attributed to the slowing down of the diffusion, which is expected at small sphere-wall separations. The feasibility of monitoring the deposition of submicroscopic latex particles using this technique was also investigated, with promising results.