Extending the range of switchable-hydrophilicity solvents

Abstract

A switchable-hydrophilicity solvent (SHS) is a solvent that in one state forms a biphasic mixture with water but can be reversibly switched to another state that is miscible with water. All of the amine SHSs that we have reported previously lie within a particular basicity and hydrophilicity range (9.5 < pK_aH < 11 and 1.0 < log K_ow < 2.5, respectively). We report an extension of this range by altering the pressure of CO₂ as well as the water : SHS volume ratio used in the process. Increasing the pressure of CO₂ and/or the water : amine volume ratio allows some amines with pK_aH < 9.5 or log K_ow > 2.5 to function as SHSs.