Amphiphile regulated ionic-liquid-based aqueous biphasic systems with tunable LCST and extraction behavior

Ionic liquid (IL)/H2O mixtures with tunable lower critical solution temperature (LCST) behavior exhibit tantalizing prospect in the field of liquid-liquid phase separation and purification. Herein, different types of amphiphiles were evaluated for the facile regulation of IL ([P4444][DMBS]) based aqueous biphasic systems (ABSs). Interestingly, the addition of zwitterionic 3-(1-dodecyl-3-imidazolio) propanesulfonate (DIPS) remarkably in-creases the phase separation temperature of IL aqueous solution, while the addition of anionic sodium dodecyl benzene sulfonate (SDBS) and dodecyl-benzenesulphonic acid (DBSA) results in decreasing of the phase sepa-ration temperature. The tunable phase separation temperature ranges from 10 to 90 C, which almost cover the full usable temperature range of ABSs. The regulation mechanism of amphiphile additives on the LCST behavior of IL/H2O mixtures was investigated through isothermal titration calorimetry, 1H NMR spectroscopy and molecular dynamics simulations. Briefly, the addition of zwitterionic DIPS increased LCST through electrostatic shielding effect, while the addition of anionic SDBS and DBSA decreased LCST through ion exchange effect. As a proof of concept, the amphiphile regulated ABSs were demonstrated to selectively separate aliphatic and aromatic amino acids.

Automated summary

Ionic liquid/water mixtures with tunable lower critical solution temperature behavior have significant implications for liquid-liquid phase separation and purification. By adding different types of amphiphiles, the phase separation temperature of the ionic liquid solution can be regulated. Zwitterionic additives increase the phase separation temperature, while anionic additives decrease it. The amphiphile-regulated system can selectively separate different types of amino acids.