SKM 2023 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 24: Complex Fluids and Soft Matter I (joint session DY/CPP)
CPP 24.11: Talk
Tuesday, March 28, 2023, 12:45–13:00, MOL 213
Coacervates from a polyelectrolye and a small polyion: preparation, phase behavior and theoretical modeling — Lucy Coria-Oriundo1, Eugenia Apuzzo2, Santiago Herrera1, Marcelo Ceolín2, Gabriel Debais1, Fernando Battaglini1, and •Mario Tagliazucchi1 — 1Universidad de Buenos Aires, Bs.As., Argentina — 2Universidad Nacional de la Plata, Bs.As., Argentina.
A mixture of oppositely charged polyelectrolytes, under the proper experimental conditions, can undergo liquid-liquid phase separation. The resulting polymer-rich phase is usually known as polyelectrolyte coacervate. This work reports liquid coacervates composed of a small polyanion (ferricyanide) and branched poly(ethyleneimine) (BPEI), a polycation. The phase diagram of the system was measured as a function of the concentration of both components at fixed pH = 6 and a concentration of added NaCl of 0.5 M. The salt resistance of the coacervate was studied and it was found that the coacervate is stable up to [NaCl] = 1.35 M. The phase diagram and salt-resistance experiments were modeled with a statistical-thermodynamics formalism that models the association of the oppositely charged species as a pseudo-chemical-equilibrium. The model fits very well the experimental data and was used to analyze the differences between polymer-polymer and polymer-small ion coacervates. Finally, the diffusion coefficient of ferricyanide within the coacervated (measured with cyclic voltammetry) was shown to increase 10 times when the concentration of added NaCl was increased from 0 to 1.2 M.