Dynamics of Na+-polystyrene sulphonate in solution at low ionic strength

The dynamics of Na + -polystyrene sulphonate (Na + PSS) (MW=10 5 ) in water of low ionic strength was investigated by photon correlation spectroscopy. The cooperative diffusion coefficient D eff obtained from the first cumulant was measured in a concentration range of five decades. The lowest concentrations are in the dilute regime. In the semidilute regime, that is for concentrations greater than the overlap concentration c* approximately=3*10 -7 monomers AA -3 , the cooperative diffusion coefficient follows a power law D eff approximately c 0.52+or-0.02 which is in good agreement with theoretical predictions for polyelectrolytes. At very high concentrations, c>c** approximately=10 -5 monomers AA -3 , a new regime, which is called the concentrated regime, is observed which shows a constant D eff . This behaviour may be explained by a scaling law, which takes the electrostatic persistence length as the fundamental parameter.