Coacervates from a polyelectrolye and a small polyion: preparation, phase behavior and theoretical modeling

MARIO TAGLIAZUCCHI

Dresden

Conferencia; Meeting of the DPG (Deutsche Physikalische Gesellschaft); 2023

Deutsche Physikalische Gesellschaft

A mixture of oppositely charged polyelectrolytes, under the properexperimental conditions, can undergo liquid-liquid phase separation.The resulting polymer-rich phase is usually known as polyelectrolytecoacervate. This work reports liquid coacervates composed of a smallpolyanion (ferricyanide) and branched poly(ethyleneimine) (BPEI), apolycation. The phase diagram of the system was measured as a function of the concentration of both components at fixed pH = 6 anda concentration of added NaCl of 0.5 M. The salt resistance of thecoacervate was studied and it was found that the coacervate is stableup to [NaCl] = 1.35 M. The phase diagram and salt-resistance experiments were modeled with a statistical-thermodynamics formalism thatmodels the association of the oppositely charged species as a pseudochemical-equilibrium. The model fits very well the experimental dataand was used to analyze the differences between polymer-polymer andpolymer-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 NaClwas increased from 0 to 1.2 M.