REVISIT TO THE INTRINSIC-VISCOSITY MOLECULAR-WEIGHT RELATIONSHIP OF IONIC POLYMERS .2. VISCOSITY BEHAVIOR OF SALT-FREE AQUEOUS-SOLUTIONS OF SODIUM POLY(STYRENESULFONATES)

The reduced viscosity of aqueous solutions of sodium poly(styrenesulfonates) of a narrow molecular weight distribution was measured with the utmost care in the absence of a coexisting salt. The possibility of adsorption of the macroions on the glass wall of the viscometer capillary was confirmed to be negligible. The shear rate dependence was quite substantial, particularly at low polymer concentrations. The reduced viscosity was extrapolated to zero shear rate. The general feature of the concentration dependence was that the extrapolated viscosity increased with increasing polymer concentration and decreased after passing a maximum, as was reported earlier by several authors. For the exponent a of the relation [η] = KMα ([η], intrinsic viscosity; M, molecular weight; and K, a constant), 1.6-1.2 was obtained for samples having molecular weights of 3.7 X 105-1.7 X 106, when use was made of the intrinsic viscosity at zero shear rate. This appears to indicate that the macroions are not fully stretched out like a rod even at the infinite dilution, if the viscosity-molecular weight relation may be used for ionic flexible macromolecules. © 1990, American Chemical Society. All rights reserved.