Ionic-Liquid-Based Aqueous Two-Phase Systems Induced by Intra- and Intermolecular Hydrogen Bonds.

Area of Science:

• Physical Chemistry
• Separation Science
• Materials Science

Background:

• Aqueous two-phase systems (ATPSs) are valuable for biomolecule separation.
• Ionic liquids (ILs) offer tunable properties for ATPS applications.
• Controlling IL phase behavior is key to optimizing separation processes.

Purpose of the Study:

• To investigate the influence of anion cis-trans isomerism in ionic liquids on their aqueous phase behavior.
• To elucidate the mechanisms governing upper critical solution temperature (UCST) and lower critical solution temperature (LCST) phenomena in IL-based ATPS.
• To demonstrate the application of these tunable ATPS for efficient amino acid separation.

Main Methods:

• Synthesis and characterization of ionic liquids with varying anion structures (cis vs. trans).
• Experimental determination of phase diagrams and critical solution temperatures (UCST/LCST) for IL-water systems.
• Analysis of temperature-dependent dissociation and molecular microstructure effects on phase behavior.

Main Results:

• Ionic liquids with cis-anions exhibited UCST behavior, while trans-anions showed LCST behavior.
• Phase transitions are attributed to temperature-dependent dissociation and steric hindrance of ILs.
• The developed IL-based ATPS demonstrated efficient separation and extraction of specific amino acids.

Conclusions:

• Anion isomerism in ILs provides a novel strategy to control ATPS phase behavior (UCST/LCST).
• Understanding the interplay between chemical equilibrium and molecular microstructure is crucial for designing IL-based ATPS.
• These systems offer a simple, effective, and environmentally friendly approach for separating small biological molecules.