title: Controlling the Formation of Ionic-Liquid-based Aqueous Biphasic Systems by Changing the Hydrogen-Bonding Ability of Polyethylene Glycol End Groups.
abstract: The formation of aqueous biphasic systems (ABS) when mixing aqueous solutions of polyethylene glycol (PEG) and an ionic liquid (IL) can be controlled by modifying the hydrogen-bond-donating/-accepting ability of the polymer end groups. It is shown that the miscibility/immiscibility in these systems stems from both the solvation of the ether groups in the oxygen chain and the ability of the PEG terminal groups to preferably hydrogen bond with water or the anion of the salt. The removal of even one hydrogen bond in PEG can noticeably affect the phase behavior, especially in the region of the phase diagram in which all the ethylene oxide (EO) units of the polymeric chain are completely solvated. In this region, removing or weakening the hydrogen-bond-donating ability of PEG results in greater immiscibility, and thus, in a higher ability to form ABS, as a result of the much weaker interactions between the IL anion and the PEG end groups.
authors.affiliation: Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487 (USA). jfbpereira@fcfar.unesp.br.|Department of Bioprocess and Biotechnology, School of Pharmacy, UNESP-São Paulo State University, 14801-902-Araraquara, SP (Brazil). jfbpereira@fcfar.unesp.br.
authors.forename: Jorge F B
authors.initials: JF
authors.lastname: Pereira
authors.affiliation: Chemistry Department, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal).
authors.forename: Kiki A
authors.initials: KA
authors.lastname: Kurnia
authors.affiliation: Chemistry Department, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal).
authors.forename: Mara G
authors.initials: MG
authors.lastname: Freire
authors.affiliation: Chemistry Department, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal).
authors.forename: João A P
authors.initials: JA
authors.lastname: Coutinho
authors.affiliation: Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487 (USA). robin.rogers@mcgill.ca.|Chemistry Department, McGill University, Montreal, QC H3 A 0B8 (Canada). robin.rogers@mcgill.ca.
authors.forename: Robin D
authors.initials: RD
authors.lastname: Rogers
mesh_terms: D006860:Hydrogen Bonding; D052578:Ionic Liquids / Q000737:chemistry*; D015394:Molecular Structure; D011092:Polyethylene Glycols / Q000737:chemistry*; D012995:Solubility; D014867:Water / Q000737:chemistry
chemical_list: D052578:Ionic Liquids; D014867:Water; D011092:Polyethylene Glycols
keywords: aqueous biphasic systems; hydrogen bonding; ionic liquids; polyethylene glycol; polymers