(608a) Effects of Charge Connectivity, Ion Binding, and Backbone Hydrophilicity on Polyelectrolyte Coacervation

We present our latest work on the modeling of polyelectrolyte coacervation by extending the standard Debye- Hückel theory of electrostatic correlation. Three physical effects known to be important are considered: charge connectivity, reversible ion binding, and backbone hydrophilicity. Charge connectivity is found to enhance the stability of the coacervate. Reversible ion binding is found to depend sensitively on the nature of charge connectivity, and its proper treatment relies on that of ionic self-energy. The backbone hydrophilicity is found to narrow the width of coacervation window. To examine this and the various competing models, we prepared nine experimental phase diagrams with varying molecular weights and degrees of backbone hydrophilicity. The data demonstrates that the molecular weight dependence of salt effects is substantially weaker than predicted by existing theories. Our theory, which incorporates all three effects above, successfully captured this trend and fits experimental phase diagrams nearly quantitatively.