Enhanced Concentration Fluctuations in Model Polyelectrolyte Coacervate Mixtures along a Salt Isopleth Phase Diagram

Published

December 8, 2021

Author(s)

Vivek Prabhu, Yuanchi Ma, Samim Ali

Abstract

A temperature (T) versus polymer concentration (cp) representation leads to non-overlapping coexistence curves prepared from different initial polymer concentrations along a salt isopleth of aqueous mixtures of charge-stoichiometric, oppositely-charged polydisperse polyelectrolytes. This effect was explained by an unequal salt concentration (cs) between equilibrating phases that improves the relationship between the common cs-cp representation to T- cp along a salt isopleth in terms of a T-cs-cp phase envelope. Further quantification of the cloud points and spinodal temperatures predicts regions of metastability and instability with critical point on a salt isopleth phase diagram. As the cloud point is approached, the correlation length for concentration fluctuations far exceeds the chain dimensions with evidence of a cross-over from mean-field to fluctuation regime. The effective critical exponents for the divergence in the osmotic compressibility, via scattered intensity to zero angle, and correlation length, gamma_eff and nu_eff, respectively deviates from the 3D Ising model. These static light scattering measurements illustrate that concentration fluctuations are enhanced by polyelectrolyte chain association near the lower critical solution temperature.

Citation

Macromolecules

Volume

54

Pub Type

Journals

Download Paper

https://doi.org/10.1021/acs.macromol.1c02001

Local Download

Keywords

polyelectrolyte, phase diagram, scattering, fluctuations

Citation

Prabhu, V. , Ma, Y. and Ali, S. (2021), Enhanced Concentration Fluctuations in Model Polyelectrolyte Coacervate Mixtures along a Salt Isopleth Phase Diagram, Macromolecules, [online], https://doi.org/10.1021/acs.macromol.1c02001, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933311 (Accessed October 14, 2025)