Polyelectrolyte Complex Coacervation across a Broad Range of Charge Densities
AE Neitzel and YN Fang and BY Yu and AM Rumyantsev and JJ de Pablo and MV Tirrell, MACROMOLECULES, 54, 6878-6890 (2021).
Polyelectrolyte complex coacervates of homologous (co)polyelectrolytes with a near-ideally random distribution of a charged and neutral ethylene oxide comonomer were synthesized. The unique platform provided by these building blocks enabled an investigation of the phase behavior across charge fractions 0.10 <= f <= 1.0. Experimental phase diagrams for f = 0.30-1.0 were obtained from thermogravimetric analysis of complex and supernatant phases and contrasted with molecular dynamics simulations and theoretical scaling laws. At intermediate to high f, a dependence of polymer weight fraction in the salt-free coacervate phase (w(P,c)) of w(P, c) similar to f(0.37 +/- 0.01) was extracted; this trend was in good agreement with accompanying simulation predictions. Below f = 0.50, w(P, c) was found to decrease more dramatically, qualitatively in line with theory and simulations predicting an exponent of 2/3 at f <= 0.25. Preferential salt partitioning to either coacervate or supernatant was found to be dictated by the chemistry of the constituent (co)polyelectrolytes.
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