Alkylimidazolium Protic Ionic Liquids: Structural Features and Physicochemical Properties

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Engineering

Background:

• Protic ionic liquids (PILs) are salts with proton transfer between ions.
• Understanding their thermal and transport properties is crucial for applications.
• Imidazolium-based PILs are widely studied due to their tunable properties.

Purpose of the Study:

• To analyze the impact of anion nature and cation alkyl chain length on PIL properties.
• To investigate the microscopic structure and cation-anion interactions in PILs.
• To compare protic ionic liquids with analogous aprotic ionic liquids.

Main Methods:

• Literature data analysis and experimental determination of thermal and transport properties.
• Density Functional Theory (DFT) calculations in gas and solvent phases.
• Comparative analysis of PILs and corresponding aprotic ionic liquids (ILs).

Main Results:

• Higher thermodynamic stability of ion pairs increases PIL decomposition temperature.
• Melting points decrease with increasing hydrocarbon radical length in the cation.
• Weaker ion-ion interactions correlate with lower melting points.
• Protic ILs exhibit lower melting points than aprotic ILs due to weakened ion-ion interactions and hydrogen bonds.

Conclusions:

• Anion nature and cation alkyl chain length significantly influence PIL thermal and transport properties.
• DFT calculations provide microscopic insights into cation-anion binding.
• Structural modifications in PILs offer a route to tune their properties for specific applications.