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Restructuring a Deep Eutectic Solvent by Water: The Nanostructure of Hydrated Choline Chloride/Urea
1Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, United States.
Journal of Chemical Theory and Computation
|April 1, 2020
Summary
Water significantly alters the nanostructure of deep eutectic solvents (DES), even at low hydration levels. Molecular dynamics simulations reveal two competing nanostructures whose balance shifts with water content, impacting DES properties.
Area of Science:
- Green Chemistry
- Materials Science
- Physical Chemistry
Background:
- Deep eutectic solvents (DES) are tunable, sustainable solvents with diverse applications.
- Understanding the impact of hydration on DES nanostructure is crucial due to their hygroscopic nature.
Purpose of the Study:
- To investigate the nanostructural changes in choline chloride-urea DES with varying water content.
- To develop a method for analyzing the local association modes within hydrated DES.
Main Methods:
- Molecular dynamics simulations using a newly parametrized force field.
- Convex constrained analysis of radial distribution functions.
Main Results:
- Water addition alters DES nanostructure even at low hydration.
- Two dominant, competing nanostructures were identified, with their prevalence changing with hydration.
- Water forms distinct clusters with DES components, including linear structures with chloride.
- At high hydration (>50 wt%), the mixture resembles an aqueous electrolyte.
Conclusions:
- The nanoscale structural evolution with hydration directly influences macroscopic DES properties.
- Understanding these hydration-induced structural changes is key to optimizing DES as solvents and for interactions with additives.
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