Since inventing switchable solvents in 2004, the author’s group and collaborators have been developing the concept to ensure that such solvents can be practical, inexpensive, and as environmentally benign as possible. While the original solvents were switchable-polarity solvents, meaning that their polarity underwent a significant change when the solvent switch was triggered, two other classes of switchable solvents are currently the focus of research in the group: switchable hydrophilicity solvents (SHS) and switchable water (SW). These will be the focus of this presentation. “Switchable-hydrophilicity solvents” normally form a biphasic mixture when mixed with water but, when exposed to CO2, these solvents become very hydrophilic and completely miscible with water (Figure 1a). SHS can be used for extractions of hydrophobic materials. The focus will be on the best method for designing the greenest possible SHS. “Switchable water” is an aqueous solution having switchable ionic strength. For example, an aqueous solution of a polyamine, in the absence of CO2, has a very low ionic strength. However, after CO2 is introduced, the polyamine changes to a bicarbonate salt, raising the ionic strength dramatically (Fig. 1b). That change in ionic strength changes the properties of the water and its performance in many applications. Applications of switchable water include: extraction solvent, media for syntheses or catalysis, controlling emulsion or suspension stability, or obtaining fresh water from seawater or wastewater by forward osmosis. The presentation will include the development of SHS and SW, with an emphasis on molecular design to minimize environmental impact and maximize efficacy for selected applications.

Switchable hydrophilicity solvents and switchable water: Design for applications and the environment

249th National Meeting (2015)

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