Translational diffusion coefficient of sodium poly(2-acrylamido-2-methylpropanesulfonate) in aqueous sodium chloride

Dynamic light scattering measurements have been made on 9 samples of sodium poly(2-acrylamido-2-methylpropanesulfonate), an intrinsically flexible, linear poly-electrolyte, ranging in weight-average molecular weight from 2.9x10(4) to 1.5x10(6) with 0.05 and 0.5 M aqueous NaCl at 25 degrees C as the solvents. The measured translational diffusion coefficients or hydrodynamic radii R-H are analyzed on the basis of the wormlike chain with excluded volume. The quasi-two-parameter theory for the hydrodynamic-radius expansion factor with the known expression for the translational friction coefficient of an unperturbed wormlike chain describes the molecular weight dependence of R-H in the aqueous salts with a degree of accuracy very similar to that known for nonionic flexible polymers in good solvents.