Determination of intrinsic viscosity of polyelectrolyte solutions

Intramolecular hydrodynamic contribution ηintra/C to the reduced viscosity ηSP/C of polyelectrolyte solutions is derived as a function of polymer concentration C by separating the theoretically calculated intermolecular electrostatic contribution ηinter/C from the observed reduced viscosity, assuming an additivity, ηSP/C=ηintra/C+ηinter/C. The resulting intramolecular part ηintra/C reflects nearly the net effect of the polyion conformation; it increases monotonously with decreasing polymer concentration and levels off to a constant in sufficiently dilute concentrations. The leveling-off value of ηintra/C corresponds to the intrinsic viscosity [η]. From the estimated values of [η], the ionic strength I dependence of the polyion conformation has been visualized, resulting in a similarity between two relations, ηintra/C vs. C and [η] vs. I.