Web Release Date: August 5,
Rheology of Sulfonated Polystyrene Solutions
Received December 30, 1997 Revised Manuscript Received June 5, 1998 Abstract: We report the apparent viscosity of aqueous solutions of a well-characterized synthetic
polyelectrolyte, the sodium salt of polystyrene sulfonate. Using two rheometers we measure the apparent
viscosity over more than five decades of shear rate to determine the Newtonian viscosity and the onset
of shear thinning, which is inversely proportional to the relaxation time. We study five decades of
polyelectrolyte concentration, from the dilute to the entangled regimes, and three decades of added salt
(NaCl) concentration, on a single polyelectrolyte sample. Much of the viscosity data in the literature are
shown to be in the shear thinning regime and are not indicative of the Newtonian viscosity. Our data
for viscosity and longest relaxation time are qualitatively consistent with a recent scaling theory. There
are systematic deviations from this simple theory, including the failure of the well-established Fuoss
law, which is shown to be obeyed by the apparent viscosity only at higher shear rates.
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