Structural and dynamical changes observed when transitioning from an ionic liquid to a deep eutectic solvent.

Area of Science:

• Physical Chemistry
• Materials Science
• Spectroscopy

Background:

• Deep eutectic solvents (DES) are tunable solvent systems with unique properties.
• Understanding the molecular structure and dynamics of DES is crucial for their application.
• Ionic liquids and amides are common components in DES formation.

Purpose of the Study:

• To investigate the microscopic molecular structure and dynamics of a novel DES.
• To explore the transition from an ionic liquid to a DES with varying amide concentrations.
• To understand the local environment and interactions within the DES.

Main Methods:

• Linear and non-linear infrared spectroscopy using a vibrational probe.
• Concentration dependence studies.
• Small-angle X-ray scattering (SAXS) experiments.

Main Results:

• The vibrational probe senses a consistent local environment regardless of cation structure.
• Amide molecules transition from isolated to interacting as concentration increases.
• Slow dynamics of the vibrational probe are affected by amide addition, indicating changes in ionic cage dynamics.
• Two dynamical regimes were observed, suggesting a nanoscopically heterogeneous environment at high amide concentrations (>1:1 molar ratio).

Conclusions:

• The DES exhibits a nanoscopically heterogeneous structure at high amide concentrations.
• Amide-amide interactions become favored at higher molar ratios.
• The study provides molecular insights into DES formation and structure-property relationships.