Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published March 13, 2018 | public
Journal Article

Polyelectrolyte Chain Structure and Solution Phase Behavior


Using a recently developed renormalized Gaussian fluctuation (RGF) field theory that self-consistently accounts for the concentration-dependent coupling between chain structure and electrostatic correlations, we study the phase behavior of polyelectrolyte solutions, with a focus on the effects of added salts and chain structure. For solutions of a single polyelectrolyte species plus salt, the RGF theory predicts the existence of a loop in the phase boundary at Bjerrum lengths (inverse temperature) below (above) the critical value of the salt-free system. This loop behavior can occur at electrostatic interaction strengths lb/b at which the loop no longer exists for the TPT-1 theory, and at fixed lb/b the loop can persist for infinitely long chains, in contrast to theories using a fixed-Gaussian structure (fg-RPA). For systems of oppositely charged (but otherwise symmetric) chains, we again find that the fg-RPA greatly overpredicts the driving force for phase separation, especially at higher charge fractions (but still below the critical Manning charge density). In general, stiff chains have a narrower two-phase region than intrinsically flexible chains, although intrinsically flexible chains can still experience a local stiffening which persists in semidilute solution; for higher charge fractions the local stiffening of flexible chains is crucial for reproducing qualitatively correct thermodynamics and phase diagrams. For fully charged flexible chains, we find that phase diagrams are quite similar to those for semiflexible rods and that it is possible to capture the coacervate phase diagrams of the full self-consistent calculations using a constant, renormalized chain stiffness.

Additional Information

© 2018 American Chemical Society. Received: December 19, 2017; Revised: January 29, 2018; Publication Date (Web): February 20, 2018. The authors thank Pengfei Zhang for helpful discussions. K.S. also gratefully acknowledges support by the NSF-GRFP Grant DGE-1745301 and the Jacobs Institute for Molecular Engineering for Medicine. The authors declare no competing financial interest.

Additional details

August 19, 2023
October 18, 2023