Different Hydrogen Bond Changes Driven by Surface Segregation Behavior of Imidazolium-Based Ionic Liquid Mixture at...

Area of Science:

• Physical Chemistry
• Materials Science
• Computational Chemistry

Background:

• Ionic liquids (ILs) are tunable solvents with unique interfacial properties.
• Understanding IL mixture behavior at interfaces is crucial for applications.
• Surface segregation in IL mixtures influences their bulk and interfacial characteristics.

Purpose of the Study:

• To investigate the interfacial behavior of a binary ionic liquid mixture ([C2C1Im][BF4] and [C4C1Im][BF4]).
• To elucidate the effects of surface segregation on hydrogen bonding and cation dynamics.
• To analyze the impact of alkyl chain length on IL mixture ordering at the liquid-vacuum interface.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• Simulations were performed for pure ILs and an equimolar binary IL mixture.
• Analysis focused on cation aggregation, hydrogen bonding, ring rotations, and orientation.

Main Results:

• Significant surface segregation of [C4C1Im]+ cations was observed due to nonpolar interactions.
• [C2C1Im]+ cations exhibited enhanced hydrogen bonding with [BF4]- anions at the interface.
• Surface segregation altered cation aggregation, hydrogen bonding, and rotational dynamics.
• Interfacial orderliness decreased for both cations in the mixture compared to pure ILs.

Conclusions:

• Nonpolar interactions drive distinct surface segregation in IL mixtures.
• Surface segregation profoundly impacts hydrogen bonding and dynamics at the IL-vacuum interface.
• These findings provide insights into the interfacial behavior of imidazolium-based IL mixtures.