Manuel Brunner1, Christopher J Garvey2, Gregory G Warr3, Rob Atkin4. 1. School of Molecular Sciences, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia. Electronic address: manuel.brunner@research.uwa.edu.au. 2. Lund Institute for Advanced Neutron and X-ray Science, 223 70 Lund, Sweden; Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany. Electronic address: christopher.garvey@mau.se. 3. School of Chemistry and University of Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: gregory.warr@sydney.edu.au. 4. School of Molecular Sciences, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia. Electronic address: rob.atkin@uwa.edu.au.
Abstract
HYPOTHESIS: Hybrid solvents based on cholinium amino acid ionic liquids ([Ch][AA] ILs) mixed with water are environmentally benign solvents with low toxicity. [Ch][AA] ILs are used in biomass pretreatment processes to dissolve targeted (macro)molecules such as lignin from lingnocellulose. Understanding how [Ch][AA] ILs dissolve polymers is therefore of great interest for the rational design of ILs towards industrial application. Variation of the IL anion and the water concentration are hypothesised to change the solvent properties of [Ch][AA] hybrid solvents. Therefore, we probe the solvent quality of [Ch][AA] aqueous solutions with different anions (glycinate, prolinate and argininate) and water concentration for the simple model solute poly(ethylene glycol) (PEG). EXPERIMENTS: Partial phase diagrams were produced to probe the salting-out effect of [Ch][AA] ILs towards PEG (Mw = 38 kDa). Small-angle neutron scattering experiments of deuterated PEG in hydrogenous [Ch][AA] aqueous solutions were performed to determine the polymer radius of gyration at infinite dilution (Rg,0) via Zimm-plots. Polymer concentration dependent apparent Rg values were obtained fitting an excluded volume polymer model onto the scattering data. Blends of hydrogenous and deuterated PEG under zero average contrast conditions were analysed to probe Rg at high polymer concentrations. FINDINGS: Hydrogen bond capacity of the anion is key to the salting-out effect of [Ch][AA] ILs on PEG. Rg,0 depends on anion species and water concentration. At IL:water = 1:30 (mole:mole) and 37 °C, cholinium argininate and cholinium glycinate are close to theta solvents while cholinium prolinate and dilute cholinium argininate (IL:water = 1:100) are between theta and good solvents.
HYPOTHESIS: Hybrid solvents based on cholinium amino acid ionic liquids ([Ch][AA] ILs) mixed with water are environmentally benign solvents with low toxicity. [Ch][AA] ILs are used in biomass pretreatment processes to dissolve targeted (macro)molecules such as lignin from lingnocellulose. Understanding how [Ch][AA] ILs dissolve polymers is therefore of great interest for the rational design of ILs towards industrial application. Variation of the IL anion and the water concentration are hypothesised to change the solvent properties of [Ch][AA] hybrid solvents. Therefore, we probe the solvent quality of [Ch][AA] aqueous solutions with different anions (glycinate, prolinate and argininate) and water concentration for the simple model solute poly(ethylene glycol) (PEG). EXPERIMENTS: Partial phase diagrams were produced to probe the salting-out effect of [Ch][AA] ILs towards PEG (Mw = 38 kDa). Small-angle neutron scattering experiments of deuterated PEG in hydrogenous [Ch][AA] aqueous solutions were performed to determine the polymer radius of gyration at infinite dilution (Rg,0) via Zimm-plots. Polymer concentration dependent apparent Rg values were obtained fitting an excluded volume polymer model onto the scattering data. Blends of hydrogenous and deuterated PEG under zero average contrast conditions were analysed to probe Rg at high polymer concentrations. FINDINGS:Hydrogen bond capacity of the anion is key to the salting-out effect of [Ch][AA] ILs on PEG. Rg,0 depends on anion species and water concentration. At IL:water = 1:30 (mole:mole) and 37 °C, cholinium argininate and cholinium glycinate are close to theta solvents while cholinium prolinate and dilute cholinium argininate (IL:water = 1:100) are between theta and good solvents.
Authors: László Almásy; Oleksandr P Artykulnyi; Viktor I Petrenko; Oleksandr I Ivankov; Leonid A Bulavin; Minhao Yan; Vasil M Haramus Journal: Molecules Date: 2022-04-15 Impact factor: 4.927