Opposite Effects Induced by Cholinium-Based Ionic Liquid Electrolytes in the Formation of Aqueous Biphasic Systems Comprising Polyethylene Glycol and Sodium Polyacrylate.

Sandra C Bernardo,Mara G Freire,Jorge F B Pereira,Emanuel V Capela,Sónia P M Ventura,João A P Coutinho

doi:10.3390/molecules26216612

Abstract

Cholinium-based ionic liquids ([Ch]-based ILs) were investigated as electrolytes in the formation of aqueous biphasic systems (ABS) composed of polyethylene glycol (PEG) and sodium polyacrylate (NaPA) polymers. Both enhancement and decrease in the liquid-liquid demixing ability induced by electrolytes in PEG-NaPA aqueous biphasic systems were observed. It is shown that the ILs that most extensively partition to the PEG-rich phase tend to act as inorganic salts enhancing the two-phase formation ability, while those that display a more significant partition to the NaPA-rich phase decrease the ABS formation capacity. The gathered results allowed us to confirm the tailoring ability of ILs and to identify, for the first time, opposite effects induced by electrolytes on the PEG-NaPA ABS formation ability. The distribution of the electrolyte ions between the coexisting phases and the polyelectrolyte ion compartmentalization are key factors behind the formation of PEG-NaPA-based ABS.

Highlights

Liquid-liquid extractions by means of aqueous biphasic systems (ABS) have been extensively explored in the last decades to recover, purify and/or concentrate a large number of biocompounds [1,2,3]
To evaluate the polyethylene glycol (PEG) molecular weight (MW) influence on the formation of PEG-NaPA-ionic liquids (ILs) ABS, the phase diagrams composed of PEG polymers with different MW
The remaining phase diagrams for systems containing the different [Ch]-based ILs combined with PEGs of different MW are given in Figure S1 in the Supplementary Material

Summary

Introduction

Liquid-liquid extractions by means of aqueous biphasic systems (ABS) have been extensively explored in the last decades to recover, purify and/or concentrate a large number of biocompounds [1,2,3]. The most commonly used polymer/-polymer pair for ABS formation is polyethylene glycol (PEG)-dextran [9,12], but dextran is more expensive in comparison with the polymers used and leads to highly viscous aqueous solutions, imposing some limitations of operability when the large-scale application of ABS is envisaged [13,14,15]. To overcome these shortcomings, polyelectrolytes have been investigated as phase-forming agents of ABS [16,17,18]. Polyelectrolyte aqueous solutions usually exhibit lower viscosity than non-ionic polymer solutions [10,18]

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Results

Conclusion