Observations upon the dynamic structure factor of interacting spherical polyelectrolytes

Experimental studies are reported on the light-scattering spectrum of 0.038 μ carboxylate-modified polystyrene latex spheres in deionized water. In concentrated suspensions, the long-time decay of the two-particle dynamic structure factor is given by a power law (t−α) form, not by a slow exponential. Nonlinear least squares fits found α≂1.2–1.5, smaller values of α corresponding to higher sphere concentrations. The reduction of the mutual diffusion coefficient of 0.15 μ spheres in mixtures of 0.15 and 0.038 μ spheres was examined, and is interpreted in terms of the dynamic friction modification to the drag coefficients. Multiple scattering artifacts were shown to be absent with homodyne coincidence spectroscopy.