Probing Conformation Effects on Structure and Dynamics of Unentangled Polyelectrolyte Solutions using Neutron Scattering

Polyelectrolytes are essential components of many biological systems as they form interpenetrating networks that make muscle tissues and influence mechanical properties. Understanding the structure and dynamics of polyelectrolyte chains under various conditions is key to decouple their complex transport phenomena. Here, we examine the effects of chain conformation, varied through ionic strength, on the structure and dynamics of sodium polystyrene sulfonate in aqueous solutions. The solution viscosities follow the predicted scaling with concentration η~c^1/2 and η~c^5/4 in the low and high salt limits, respectively. The dynamics of chains with similar structural properties behave similarly, and we observe two scaling regimes of the relaxation rate as a function of wavevector that reflect segmental and collective chain dynamics at small and large length scales, respectively. We compare our data across the existing predictions of Rouse (weak hydrodynamic interactions, > ξ) and Zimm (strong hydrodynamics, < ξ). The Rouse-Zimm scaling predictions, however, are not capable of quantitatively describing our relaxation rates or collapsing our scattering data, suggesting that the electrostatic interactions on polyelectrolyte chains influence the underlying assumptions of traditional models.