Transport Mechanism of Acetamide in Deep Eutectic Solvents

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Engineering

Background:

• Deep eutectic solvents (DESs) are promising alternatives to ionic liquids in various applications.
• High viscosity and poor conductivity limit the industrial use of DESs.
• Understanding the molecular origins of transport properties is crucial for DES improvement.

Purpose of the Study:

• To investigate the nanoscopic diffusion mechanism of acetamide in a DES.
• To elucidate the molecular reasons behind the transport properties of DESs.
• To develop a validated diffusion model for acetamide-based DES (ADES).

Main Methods:

• Neutron scattering experiments.
• Molecular dynamics (MD) simulations.
• Construction and validation of a diffusion model.

Main Results:

• A diffusion model revealed two processes: long-range jump diffusion and localized diffusion.
• Acetamide diffusion in ADES is significantly slower than in molten acetamide.
• Localized diffusion geometry is similar, but dynamics are slower in ADES.
• Both diffusion types exhibit Arrhenius temperature dependence in ADES.

Conclusions:

• Hydrogen bond-mediated complexation between acetamide and ionic species restricts long-range diffusion.
• Complex formation is the primary cause of high viscosity in ADES.
• Complexation also explains the reduced freezing point and inhibited crystallization of ADES.