Trace water-induced anomalous diffusion in chlorinated imidazolium ionic liquids

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Ionic liquids (ILs) are tunable solvents with unique properties.
• Water content significantly impacts IL behavior.
• Understanding water's effect on IL diffusion is crucial for applications.

Purpose of the Study:

• To investigate the anomalous diffusion behavior of imidazolium-based ionic liquids in the presence of trace water.
• To elucidate the molecular mechanisms governing this non-monotonic diffusion change.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• Simulations focused on imidazolium-based ionic liquid-water mixtures.
• Hydrogen bond analysis was performed to assess network dynamics.

Main Results:

• Trace water induced a non-monotonic change in IL diffusion coefficients: an initial decrease followed by an increase.
• This anomalous trend correlated with weighted hydrogen bond lifetime.
• The stability of the hydrogen-bond network, not just bond number or energy, dictates the diffusion behavior.

Conclusions:

• The diffusion of ionic liquids in aqueous mixtures is complex and non-linear.
• Hydrogen bond lifetime is a key parameter for understanding water's influence on IL dynamics.
• Findings provide insights into designing IL-water systems for specific applications.