Dynamics of Na+-Polystyrene Sulfonate in Solution at Low Ionic Strength

Abstract

The dynamics of Na+-Polystyrene-Sulfonate (Na+-PSS) of molecular weight 105 in water of low ionic strength was investigated by photon correlation spectroscopy. The cooperative diffusion coefficient obtained from the first cumulant was measured in a concentration range of five decades. Concentrations range from the dilute (c > c*) to the semi dilute (c* > c > c**)3 to the concentrated regime. The overlap concentration is c*≈ 10–4 g/cm3 which corresponds to 3 x 10–7 monomers/Å3 It is in good agreement with the overlap concentration calculated for fully extended rodlike molecules. In the dilute regime, the diffusion coefficient is smaller than the one of a gaussian coil. This may be explained by the assumption of a rodlike shape of the molecule. In the semi dilute regime the cooperative diffusion coefficient follows a power law Deff ≈ c 0.52 ± 0.02 in good agreement with theoretical predictions for polyelectrolytes.KeywordsPhoton Correlation SpectroscopyFluid MechanicsScaling BehaviorConcentrate RegiScreening LengthThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.