Molecular Dynamics Study of the O-Alkylated Amidium Ionic Liquid based Aqueous Two-Phase System

Abstract

The phase separation behaviors of water and hydrophobic ionic liquids (ILs), which are amide-based O-alkylated cation (O-ethyl-dimethylacetamidium (EDEA), O-methyldimethylacetamidium (MDEA), O-methyl-dimethylformamidium (MDMF) and O-methyl- 1-ethylpyrrolidinonium (MEPyr)) cations and trifluoromethanesulfonate (TfO-) anion mixtures, were investigated via molecular dynamics simulation. Force field parameter sets for ILs were validated by calculating thermodynamic properties such as density, viscosity and solubility parameter of each IL. Phase separation behavior of water-IL mixture was observed through tens of nanoseconds of simulation. Demixing indexes and interaction energies of water-ion were calculated for each water-IL system to quantify miscibility of ILs. Moreover, structural characteristic of solvation shell of IL cation and anion was analyzed by radial distribution function. Properties and phase separation behavior of ILwater mixtures were confirmed with respect to molecular level, which can be applied to the extraction of heavy metal ions using ILs.