Thermodynamic Insights into Polyelectrolyte Complexation: A Theoretical Framework

Abstract: In this study, we propose a theoretical framework to investigate the interactions between flexible polymer chains, specifically polyelectrolytes (PEs). By calculating the system's free energy while considering position-dependent mutual interactions and chain conformations, we gain insights into the local dielectricity as PEs overlap. Our analysis reveals that the thermodynamic drive for complex coacervation is influenced by factors such as the number of ions bound to the polymer backbone and the entropy associated with free ions, challenging earlier assumptions about the relationship between entropy gain and electrostatic temperature. We demonstrate that global thermodynamic behavior is strongly influenced by local factors like dielectric constant, providing clarity on discrepancies between experimental and computational studies. Additionally, we found that entropy gain is inversely proportional to the local dielectric constant, assuming a constant electrostatic temperature. Our findings highlight the importance of considering polymer-specific parameters when exploring the thermodynamic behavior of charged polymer complexation.