Effect of Ion Pair on Contact Angle for Phosphonium Ionic Liquids

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Engineering

Background:

• Wettability of ionic liquids (ILs) is crucial for their diverse applications.
• A detailed understanding of how cation-anion interactions influence IL wettability is still developing.

Purpose of the Study:

• To investigate the impact of cation-anion pairs on the wettability of phosphonium-based ionic liquids.
• To elucidate the mechanistic relationship between IL structure and surface interactions.

Main Methods:

• Contact angle measurements were performed experimentally.
• Classical molecular dynamics simulations were employed to model IL-surface interactions.
• Analysis of adhesive and cohesive energies provided mechanistic insights.

Main Results:

• Contact angle increased in the order benzoate < salicylate < saccharinate for the studied anions.
• Simulations revealed a decrease in contact angle with increasing alkyl chain length on the phosphonium cation.
• Atomic-scale differences between cations and anions were correlated with observed wettability trends.

Conclusions:

• Both cation structure and anion identity significantly influence the wettability of phosphonium ILs.
• The findings provide a mechanistic basis for tailoring ILs for specific surface applications.
• This study advances the understanding of structure-property relationships in ionic liquids.