(523b) Reproducible Measurements of Linear Viscoelasticity of Polyelectrolyte Coacervates in the Low-Frequency Region, Including Emergence of a Low-Frequency Plateau

We here report quantitative linear viscoelastic characterization of polyelectrolyte coacervates (PECs) formed by mixing opposite charged polyelectrolytes and apply superpositions for different ionic strengths, temperatures, and hydration levels. Some of these superpositions fail in the low frequency region due to emergence of a low-frequency plateau or a decreasing slope of storage moduli as a function of frequency. Since some moduli measurements in the low frequency region reported in the literature and in our work are close to the torque limit of the rheometer, we carefully assess the accuracy and reproducibility of rheological data as a function of frequency and establish methods for distinguishing reliable linear rheological data for these materials that are free from artifacts due to geometry, strain level, deformation history, sample preparation and aging histories. The effect of salt concentrations, polymer chain length, aging and temperature on the low-frequency region will also be discussed.