abstract
New polyethylene glycol (PEG)/ionic liquid aqueous biphasic systems (ABS) are presented. Distinct pairs of PEG polymers and ionic liquids can induce phase separation in aqueous media when dissolved at appropriate concentrations. Phase diagrams have been determined for a large array of systems at 298, 308 and 323 K. A comparison of the binodal curves allowed the analysis of the tunable structural features of the ionic liquid (i.e., anionic nature, cationic core, cationic alkyl side chain length and functionalisation, and number of alkyl substituents in the cation) and the influence of the molecular weight of the PEG polymer on the ability of these solutes to induce an ABS. It was observed that contrary to typical ABS based on ionic liquids and inorganic salts, in which the phase behaviour is dominated by the formation of the hydration complexes of the ions, the interactions between the PEG polymers and ionic liquids control the phase demixing in the polymer-type ABS studied herein. It is shown that both the ionic liquids and PEG polymers can act as the salting-out species; that is, it is an occurrence that is dependent on the structural features of the ionic liquid. For the first time, PEG/ionic liquid ABS are reported and insight into the major interactions that govern the polymer/ionic liquid phase behaviour in aqueous media are provided. The use of two different nonvolatile and tunable species (i.e., ionic liquids and PEG polymers) to form ABS allows the polarities of the phases to be tailored. Hence, the development of environmentally friendly separation processes that make use of these novel systems is envisaged.
keywords
HUMAN-SERUM ALBUMIN; 2-PHASE SYSTEMS; PHYSICOCHEMICAL PROPERTIES; MUTUAL SOLUBILITIES; REACTION MEDIA; TEMPERATURE; EXTRACTION; PARTITION; IMIDAZOLIUM; WATER
subject category
Chemistry
authors
Freire, MG; Pereira, JFB; Francisco, M; Rodriguez, H; Rebelo, LPN; Rogers, RD; Coutinho, JAP
our authors
Jorge Fernando Brandão Pereira
PhD Student
Mara Guadalupe Freire Martins
Coordinating ResearcherGroups
G4 - Renewable Materials and Circular Economy
G5 - Biomimetic, Biological and Living Materials
acknowledgements
The authors are grateful to Fundacao para a Ciencia e a Tecnologia for the postdoctoral scholarship SFRH/BPD/41781/2007 (M.G.F.) and the PhD scholarship SFRH/BD/60228/2009 (J.F.B.P.). M.F. and H.R. acknowledge the Ministerio de Ciencia e Innovacion of Spain for support through the FPI program (BES-2007-16693) and the