Unusual Hydration Properties of Choline Fluoride-Based Deep Eutectic Solvents

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Deep eutectic solvents (DES) are gaining traction as sustainable alternatives in various chemical applications.
• Understanding the hydration behavior of DES is crucial for optimizing their performance in aqueous mixtures.

Purpose of the Study:

• To investigate and compare the hydration properties of a fluoride-based DES (ethalineF) with a chloride-based DES (ethaline).
• To analyze the influence of water on the structural and interactive properties of these DES.

Main Methods:

• Density measurements of ethalineF and its mixtures with water across a temperature range (298–323 K).
• Calculation of excess properties (molar volumes, partial molar volumes) and viscosity deviations.
• Fitting experimental data using the Redlich-Kister equation.

Main Results:

• Negative excess molar volumes and viscosity deviations indicate strong solvation interactions in ethalineF/water and ethaline/water mixtures.
• Excess partial molar volumes suggest preferential solvation of water molecules by the DES.
• Disruption of DES interactions by water correlates with peak ionic conductivity.

Conclusions:

• Fluoride-based ethalineF exhibits distinct hydration behavior compared to chloride-based ethaline.
• The study provides insights into the structure-property relationships of DES in aqueous solutions.
• Findings are relevant for designing DES with tailored properties for specific applications, particularly those involving ionic conductivity.