Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents

Area of Science:

• Physical Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Deep eutectic solvents (DESs) are gaining attention for their unique properties.
• The role of glass formation and dipolar reorientational motions in DESs is often underestimated.
• These dynamics significantly impact room-temperature physiochemical properties.

Purpose of the Study:

• To investigate the effects of glass formation and dipolar dynamics on ionic conductivity in DESs.
• To explore the relationship between these dynamics and the mechanical properties of DESs.
• To analyze three carboxylic acid-based natural DESs: oxaline, maline, and phenylaceline.

Main Methods:

• Broadband dielectric spectroscopy
• Rheological spectroscopy
• Analysis over a wide temperature range

Main Results:

• Evidence of glass transition observed in the temperature dependence of dipolar reorientational and structural dynamics for all three DESs.
• Motional decoupling observed between different dynamics.
• Walden rule breakdown near the glass-transition temperature in maline and oxaline.
• Power-law relationship between dc conductivity and dipolar relaxation time in maline and phenylaceline.

Conclusions:

• Glass-forming properties of DESs critically influence orientational dipolar motions and rheological properties.
• These dynamics also affect dc conductivity at room temperature, highlighting technical relevance.
• Findings provide fundamental insights into DES behavior and potential for applications.