A Model for Salt Effects on Semidilute Polyelectrolyte Solutions: Equilibrium and Dynamics

Polyelectrolyte (PE) solutions are endowed with both viscous and elastic properties that differ significantly from uncharged polymer solutions. Owing to their universal existence and functionalities in biology and industry, PE solution physics have been widely studied yet are often restricted to specific assumptions, such as the presence of a theta solvent, rod/flexible chain configurations or weakly/strongly charge conditions. Here, we will present a theoretical model based on mean-field theory, which provides new insights and scaling laws for the chain conformation, relaxation time and viscosity of semidilute PE solutions in good solvents. By considering the elastic, excluded volume, and electrostatic energies due to the PE charges and double layer, our theoretical predictions agree well with experiments and offer interpretations for previously unexplained viscoelastic behavior of PE solutions in either high polymer density regimes or conditions with added salt. New criteria for the overlap concentration and other special regimes with varying salt concentrations and polymer density will also be discussed.