Enhanced Concentration Fluctuations in Model Polyelectrolyte Coacervate Mixtures along a Salt Isopleth Phase Diagram
Vivek Prabhu, Yuanchi Ma, Samim Ali
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.
, Ma, Y.
and Ali, S.
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 September 22, 2023)