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SynopsisA method was developed that, allowed comparison of the stifftiess of the chain i i i different polyelectrolytes from measurements of the intrinsic viscosity at different cotic.eiitrations of added monovalent (sodium) salt. The response to salt was quantitatively expressed as the slope of straight lines relating t.he intrinsic viscosity to the reciprocal of the square-root of the ionic strength. This slope increased considerably with increasing molecular weight of the polyelectrolyte, arid could serve to characterize the response to salt of different substances only when comparison was made a t a constant molecular weight.. An empirical parameter, B, which is the slope corresponding to an intrinsic viscosity of 1 .O a t an ionic strength of 0.1 ;\I could be correlated to the unperturbed dimensions of the molecules. A method of extrapolation, etiabliiig the determination of B from measurements of viscosity on only one sample of unknown molecular weight, was evaluat,ed.The empirically found correlation between B and some well established parameters of stiffness did not contrast predictions from the "fuzzy-sphere model" of Fixniaii, provided that reasonable assumptioiis regardiiig ion-binding and the interaction between polymer and solvent were made.

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