(468f) Time-Ionic Strength Superposition - a Unified Description of Chain Relaxation Dynamics in Polyelectrolyte Complexes

Chain relaxation dynamics and viscoelastic response of polyelectrolyte complexes (PECs) are routinely modulated by addition of salt. In this presentation, we will show that the concentration of intrinsic ions that accompany the oppositely charged polyelectrolyte chains presents a useful, yet relatively unexplored parameter for tuning the PEC viscoelastic response. Dynamic shear responses of PECs prepared with varying polyelectrolyte and added salt concentrations will be shown to collapse onto a universal master curve following a time-ionic strength superposition (TISS). The TISS master curve will be shown to enable a unified description of the PEC viscoelastic response in terms of the solution ionic strength, that accounts for both the intrinsic and the added ions, and highlight the dynamic similarities between PECs and semi-dilute polymer solutions. The sticky electrostatic associations among the oppositely charged chains, however, contribute additional relaxation modes in the PECs. We will demonstrate that the timescales of these additional relaxation modes are described quantitatively by a modified sticky Rouse model that accounts for the influence of solution ionic strength on the electrostatic screening and chain friction.