Polymer solution dynamics may be inferred from light scattering spectra of dissolved optical probe particles. We compare a variety of probes in solutions of several polymers. In the "overlapping" concentration/molecular weight regime, the Stokes-Einstein equation fails by up to a factor of 2, while the probe diffusion coefficient D follows a scaling law D / Do = exp( -aM" C V Rfj) (c, M, and R are the polymer concentration, molecular weight, and the probe radius, respectively). Experimentally, r = 0.8 ± 0.1, v = 0.6-1.0, and /) = -0.1 to 0, contrary to the theoretical predictions r = 0 and /) = 1. With very high molecular-weight polymers, we observe a further "entangled" regime, characterized by huge (10 4 ) failures of the Stokes-Einstein equation and the appearance of "fast" modes in the scattering spectrum.
The diffusion coefficient D of polystyrene latex spheres in bovine serum albumin:water was studied as a function of protein concentration c for 0 < c < 200 g/liter. The Stokes-Einstein equation for D fails by as much as 25 to 50%, D being larger than predicted from the sphere radius R and the solution viscosity. Probe particles with R as large as 0.62 um were used. D fits well to the form D = Doexp(-acO for a = 0.004 to 0.008 and v = 0.96 to 0.99. Serum albumin is a globular protein, so chain entanglement cannot cause these non-Stokes-Einsteinian effects, which are presumably due to sphere:albumin interactions. Polystyrene spheres in semidilute polyethylene oxide:water (G. S.
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