Influence of dipolar solvent fluctuations on polyelectrolyte thermodynamics and complex coacervation

We present a self-consistent polyelectrolyte field theory that reveals the impact of solvent polarity and polymer semiflexibility on polyelectrolyte solution thermodynamic behavior. Our approach incorporates a microscopic treatment of the solvent dipolar field and focuses on the importance of the charge separation distance in the dipole solvent. Consequently, this leads to an inhomogeneous dielectric medium at microscopic length scales and a significant free-energy contribution that manifests as the insolubility of uncharged species in a polar solvent. We then add the Born solvation energies of each charged species to account for their inherent solubility. Using this updated theory, which incorporates quadratic-order concentration fluctuation corrections, we generate phase diagrams for oppositely charged polyelectrolyte solutions that display phase re-entrant behavior for weakly charged polyelectrolytes and capture phase behavior consistent with recent experimental findings.