Chain Stiffness and Excluded-Volume Effects in Polyelectrolyte Solutions: Characterization of Sodium Poly(2-acrylamido-2-methylpropanesulfonate) in Aqueous Sodium Chloride

Fourteen samples of sodium poly(2-acrylamido-2-methylpropanesulfonate) ranging in weight-average molecular weight from 1.7×103 to 1.4×106 have been studied by static light scattering (or sedimentation equilibrium) and viscometry to characterize the polyelectrolyte in 0.05 and 0.5 M aqueous NaCl at 25 °C. The measured intrinsic viscosities (except for the two lowest molecular weights) and radii of gyration in the respective solvents are consistently described by combinations of the theories for unperturbed wormlike chains and excluded-volume effects (in the quasi-two-parameter scheme) with the parameter sets: q (the total persistence length) = 1.5 nm, ML (the linear mass density) = 900 nm−1, d (the chain diameter) = 1.6 nm, and B (the excluded-volume strength) = 3 nm in 0.5 M aqueous NaCl and q=3.0 nm, ML=900 nm−1, d=1.7 nm, and B=6.2 nm in 0.05 M aqueous NaCl. It is shown that the end effect on the electrostatic persistence length hardly affects the estimation of q in the aqueous salts.