Effect of Water on a Hydrophobic Deep Eutectic Solvent

Area of Science:

• Materials Science
• Physical Chemistry

Background:

• Deep eutectic solvents (DESs) are emerging as versatile solvents.
• Both hydrophilic and hydrophobic DESs absorb ambient water, forming ternary mixtures.
• Understanding water's impact on DES properties is crucial for their application.

Purpose of the Study:

• To investigate the effects of low water content on a hydrophobic DES (tetrabutyl ammonium chloride:decanoic acid, 1:2 mole ratio).
• To elucidate the molecular mechanisms behind water-induced property changes.
• To assess the implications for DES applications.

Main Methods:

• Multinuclear NMR spectroscopy
• Molecular modeling and simulations
• Physicochemical characterization techniques

Main Results:

• Low water content induces dynamic nanoscale phase segregation.
• Water reduces viscosity and fragility, increases self-diffusion and conductivity.
• Water disrupts hydrogen bonding, enhancing ion pairing and local dynamics.
• Simulations reveal structural changes with varying component ratios.

Conclusions:

• Water significantly alters DES physical properties, often beneficially for applications.
• An acidic aqueous nanophase with high halide concentration is formed, posing potential chemical risks.
• Careful consideration of water content is necessary for optimal DES utilization.