RELATIONSHIP BETWEEN SHORT-TIME SELF-DIFFUSION AND HIGH-FREQUENCY VISCOSITY IN CHARGE-STABILIZED DISPERSIONS

Experimental determination of both the shea-time self-diffusion coeffi cient and the high-frequency viscosity are reported for model charge-s tabilized dispersions. Despite the charged nature of the particles, we find that both quantities are insensitive to direct interparticle int eractions. Quantitative agreement between the experimental data and mi cromechanical hard sphere theory is observed for a range of particle s izes and added salt content. However, while the reciprocal of the shor t-time self-diffusion coefficient shows a similar concentration depend ence as the high-frequency viscosity, the two do not obey a generalize d Stokes-Einstein relation. The violation is due to subtle differences in hydrodynamic interactions between the two particle motions, in agr eement with theory and simulation. [S1063-651X(98)50310-8].