Aqueous two-phase systems (ATPS) can be created by joining aqueous solutions of two or more salts (including ionic liquids), a salt and a polymer, or two polymers, where each of the ingredients has a good solubility in water but their mutual solubility is compromised. As a result, they phase split and two aqueous phases are formed that are (partially) immiscible. These ATPS have received attention as mild extraction systems with possible applications for pharmaceuticals and bio-based chemicals that denature in organic solvents. Often, these systems are temperature-responsive and may also exhibit lower critical solution temperature (LCST) behavior. Next to the macroscopic phase behavior, also on the molecular level changes occur when stimuli are applied, and these stimuli may trigger large changes in partitioning over the phases. Such temperature-dependent partitioning can be applied to switch back and forth the catalyst from one phase to another, and realize catalyst recovery by doing so. Next to temperature, other stimuli such as pH may be used to manipulate partitioning of solutes in these systems. A few studies on stimuli responsive ATPS will be discussed and then an outlook for catalytic applications will be presented. These studies include switching of ethyl butyl amine (EBA) using either temperature or CO2 as stimulus, and the partitioning of lysozyme over a complex coacervate phase and the supernatant. We have studied EBA for extraction of lipids from microalgae and have extensively investigated on the phase behavior. Similar to EBA, catalytic complexes containing amine functionality may be phase-switched upon an external stimulus. Complex coacervates are aqueous phases that are formed by coacervation of poly electrolytes, and co-exist next to the supernatant phase. As such, they can be seen as a special class of ATPS, and recently it has been shown that proteins such as lysozyme can be triggered to partition into the complex coacervate, and also out again. This behavior may also be of use in aqueous catalytic systems.

Stimuli responsive partitioning in aqueous two-phase systems and opportunities for catalyst recycling

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.