Viscoelastic Relaxation Behavior of Polyelectrolyte Complexes from Coacervate to Precipitate

The relaxation dynamics of polyelectrolyte complexes slows down while transitioning from coacervate to precipitate upon decreasing salt concentration. However, knowledge of such changes over full relaxation spectrum is still limited. This presentation will describe the relaxation behavior of complexes probed over a wide timescale by measuring viscoelastic spectra and zero-shear viscosities at varying temperatures, salt concentrations and molecular weights using a set of model polyelectrolytes. Our studies show that the complexes exhibit time-temperature superposition (TTS) at all salt concentrations, while the range of overlapped-frequencies for time-temperature-salt superposition (TTSS) strongly depends on the salt concentration and gradually shifts to higher frequencies as the complex approaches precipitate phase. Further understanding of this transition using the sticky Rouse model and simulations studies will be presented.