Thermodynamic Insights into Polyelectrolyte Complexation: A Theoretical Framework

TL;DR

This paper develops a theoretical framework to understand the thermodynamics of polyelectrolyte complexation, emphasizing local dielectric effects and ion binding, which clarifies experimental and computational discrepancies.

Contribution

It introduces a novel theoretical approach that accounts for local dielectric variations and ion interactions, advancing understanding of polyelectrolyte complex thermodynamics.

Findings

Thermodynamic drive is affected by ion binding and free ion entropy.

Local dielectric constant influences global thermodynamic behavior.

Entropy gain is inversely proportional to local dielectric constant.

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.