Thermodynamic Framework for Water in Deep Eutectic Solvents and Ionic Liquids

Area of Science:

• Electrochemistry
• Physical Chemistry
• Materials Science

Background:

• Water content critically influences deep eutectic solvents (DESs) and ionic liquids (ILs) properties.
• Traditional methods of controlling water content lack precision in describing molecular interactions.
• Total water content alone is insufficient for understanding reactivity in DES- and IL-water mixtures.

Purpose of the Study:

• To highlight water activity as a superior descriptor for DES- and IL-water mixtures.
• To establish a thermodynamically rigorous approach for quantifying water's influence.
• To link measurable properties to molecular interactions in these solvent systems.

Main Methods:

• Conceptual analysis of water's role in nonaqueous solvents.
• Thermodynamic principles applied to solvent mixtures.
• Correlation of physical properties with molecular interactions.

Main Results:

• Water activity provides a more rigorous quantification of water's influence than total water content.
• Water activity directly relates to measurable physical properties (vapor pressure, density, viscosity, conductivity, electrochemical stability).
• Water activity correlates with solvent structure and thermodynamic excess properties.

Conclusions:

• Water activity is a critical parameter for tuning and understanding DESs and ILs.
• This descriptor enhances the prediction and control of solvent behavior.
• It offers a pathway to optimize solvent performance in various applications.