~'-potentials of a silica suspension and three types of polystyrene latex suspensions with different surface charge groups were measured, as a function of the particle concentration (~) in the suspension over a wide range, using the colloid vibration potential (CVP) technique. The concentration dependence of the F-potential in silica suspension is explained well by Levine et al.'s [1] cell model theory, verifying the applicability of the cell model to the CVP in silica suspension. However, the ~'-potentia! of latex suspensions ordinarily decreases as the particle concentration increases, even after being corrected by the term of (1-r This tendency is especially noticeable in the systems that have particles with high surface charge densities. Furthermore, the conductivity measurements of these suspensions reveal that the conductivity of these systems, especially in their highly charged state, increases as the particle concentration is increased; opposite in tendency to silica suspensions. These new findings can be explained as follows: on the highly charged surface of a latex particle, a polyelectrolyte-like ("hairy") layer is present, which overlaps at some point. This permits interparticle surface conduction and results in the abnormal behavior of CVP in these systems.

No abstract