TY - JOUR

T1 - Peek inside the water mixtures of ionic liquids at molecular level: Microscopic properties probed by epr spectroscopy

AU - Ivanov, Mikhail Yu

AU - Polienko, Yuliya F.

AU - Kirilyuk, Igor A.

AU - Prikhod’ko, Sergey A.

AU - Adonin, Nicolay Yu

AU - Fedin, Matvey V.

N1 - Funding Information: This work was supported by Russian Science Foundation (grant No. 19-13-00071). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2021/11/1

Y1 - 2021/11/1

N2 - Many ionic liquids (ILs) can be mixed with water, forming either true solutions or emulsions. This favors their applications in many respects, but at the same time might strongly alter their physicochemical properties. A number of methods exist for studying the macroscopic properties of such mixtures, whereas understanding their characteristics at micro/nanoscale is rather challenging. In this work we investigate microscopic properties, such as viscosity and local structuring, in binary water mixtures of IL [Bmim]BF4 in liquid and glassy states. For this sake, we use continuous wave and pulse electron paramagnetic resonance (EPR) spectroscopy with dedicated spin probes, located preferably in IL-rich domains or distributed in IL-and water-rich domains. We demonstrate that the glassy-state nanostructuring of IL-rich domains is very similar to that in neat ILs. At the same time, in liquid state the residual water makes local viscosity in IL-rich domains noticeably different compared to neat ILs, even though the overwhelming amount of water is contained in water-rich domains. These results have to be taken into account in various applications of IL-water mixtures, especially in those cases demanding the combinations of optimum micro-and macroscopic characteristics.

AB - Many ionic liquids (ILs) can be mixed with water, forming either true solutions or emulsions. This favors their applications in many respects, but at the same time might strongly alter their physicochemical properties. A number of methods exist for studying the macroscopic properties of such mixtures, whereas understanding their characteristics at micro/nanoscale is rather challenging. In this work we investigate microscopic properties, such as viscosity and local structuring, in binary water mixtures of IL [Bmim]BF4 in liquid and glassy states. For this sake, we use continuous wave and pulse electron paramagnetic resonance (EPR) spectroscopy with dedicated spin probes, located preferably in IL-rich domains or distributed in IL-and water-rich domains. We demonstrate that the glassy-state nanostructuring of IL-rich domains is very similar to that in neat ILs. At the same time, in liquid state the residual water makes local viscosity in IL-rich domains noticeably different compared to neat ILs, even though the overwhelming amount of water is contained in water-rich domains. These results have to be taken into account in various applications of IL-water mixtures, especially in those cases demanding the combinations of optimum micro-and macroscopic characteristics.

KW - Emulsions

KW - EPR spectroscopy

KW - Green chemistry

KW - Ionic liquids

KW - Nanostructure

KW - Viscosity

KW - Electron Spin Resonance Spectroscopy/methods

KW - Hydrogen Bonding

KW - Micelles

KW - Hydrophobic and Hydrophilic Interactions

KW - Water/chemistry

KW - Ionic Liquids/chemistry

UR - http://www.scopus.com/inward/record.url?scp=85118251100&partnerID=8YFLogxK

U2 - 10.3390/ijms222111900

DO - 10.3390/ijms222111900

M3 - Article

C2 - 34769336

AN - SCOPUS:85118251100

VL - 22

JO - International Journal of Molecular Sciences

JF - International Journal of Molecular Sciences

SN - 1661-6596

IS - 21

M1 - 11900

ER -