Influence of dipolar solvent fluctuations on polyelectrolyte thermodynamics and complex coacervation

Area of Science:

• Thermodynamics of polymer solutions
• Physical chemistry of polyelectrolytes
• Dielectric effects in polar solvents

Background:

• Understanding polyelectrolyte solution behavior is crucial for various applications.
• Existing theories often overlook the microscopic dielectric effects of polar solvents.
• Polymer semiflexibility and solvent polarity are key factors influencing phase separation.

Purpose of the Study:

• To develop a self-consistent polyelectrolyte field theory.
• To investigate the impact of solvent polarity and polymer semiflexibility on thermodynamic behavior.
• To explain the insolubility of uncharged species and the solubility of charged species in polar solvents.

Main Methods:

• Incorporation of a microscopic treatment of the solvent dipolar field.
• Inclusion of Born solvation energies for charged species.
• Application of quadratic-order concentration fluctuation corrections.

Main Results:

• The theory reveals an inhomogeneous dielectric medium at microscopic scales.
• A significant free-energy contribution explains the insolubility of uncharged species.
• Phase diagrams for oppositely charged polyelectrolyte solutions exhibit phase re-entrant behavior.

Conclusions:

• The developed theory accurately captures polyelectrolyte solution behavior.
• It provides a framework for understanding phase separation driven by solvent-dielectric properties.
• The findings align with recent experimental observations in polyelectrolyte systems.