Cosolvent control of upper and lower critical solution temperature behavior in polyelectrolyte complexes

Complex coacervate solutions composed of a blend of oppositely charged polyelectrolytes exhibit liquid-liquid phase separation upon heating or lower critical solution temperature [1,2], as found in many water-soluble uncharged polymers. It was shown that cosolvents mixtures can non-monotonically control the critical salt concentration and explained by a cross-over in electrostatic-driven and solvophobic-driven phase separation for aqueous mixture with ethylene glycol or N-methylformamide[3]. Such solvent mixtures offer an approach to tune the processability and phase separated structure of polyelectrolytes mixtures for membrane and coacervate particle applications. This presentation will discuss the effect of cosolvent mixtures on the associative and segregative phase separation of charge stoichiometric mixtures of sodium poly(acrylic acid)/quaternary poly(N,N-dimethylamimoethyl methacrylate chloride) (NaPA/qPDMAEMACl) that exhibit both lower and upper critical solution temperatures, respectively. Cloud point curves, nuclear magnetic resonance, and static and dynamic laser light scattering are used to quantify the miscibility envelope, polymer concentrations in each phase and evolution of structure that will be compared to neutral and charged polymer systems.



[1] Y. Ma, S. Ali, and V.M. Prabhu, Macromolecules 54, 11338 (2021).

[2] A. Ylitalo, C. Balzer, P. Zhang, and ZG Wang Macromolecules 54,11326 (2021).

[2] Y. Ma, R.J.S. Ivancic, J. Obrzut, D.J. Audus, V.M. Prabhu, Soft Matter 20, 7512 (2024).