Material design of ionic liquids to show temperature-sensitive LCST-type phase transition after mixing with water

Abstract

Phosphonium cations bearing different alkyl chains were coupled with several common anions so as to prepare ionic liquids (ILs) with diverse hydrophobicity. A temperature-driven phase behaviour of the mixture of various ILs and water has been examined. A few ILs were found to exhibit temperature-sensitive lower critical solution temperature (LCST)-type phase transition after mixing with water. The phase separation temperature (T c ) of the IL/water mixtures depended strongly on the hydrophobicity of the component ions as well as mixing ratio. The number of water molecules per ion pair in the IL phase (m water ) increased dramatically upon cooling. The temperature dependence of this parameter was found to be useful to predict the possibility of the ILs to show the LCST-type phase behaviour after mixing with water. Since the value of m water depended on the ion structure, especially on the hydrophobicity, the T c was accurately set out by suitably mixing two ILs with different hydrophobicity.

Sponge-like ionic liquids: a new platform for green biocatalytic chemical processes

“…38 In agreement with the structural studies above mentioned, these unique features can be schematized according to Fig 6, being a consequence of ability of the well-defined structure of these ILs to be modified by incorporating the non-polar solute in specific regions that become expanded. ethylammonium hydrogen sulfate, ethylammonium formate, etc.)…”

Amphiphilic and Phase‐Separable Ionic Liquids for Biomass Processing

“…This circumvents the need for IL distillation completely and potentially offers considerable reduction in process energy costs. [19][20][21] Abe et al [22] have demonstrated the use of tetrabutylphosphonium hydroxide (60 wt %) for the dissolution of cellulose at room temperature. Recently, we submitted a patent application that describes this concept, [14] in which phosphonium-based ILs in combination with cosolvents allowed cellulose solubility.…”

Effects of constituent ions of a phosphonium-based ionic liquid on molecular organization of H2O as probed by 1-propanol: tetrabutylphosphonium and trifluoroacetate ions

“…7 The electric conductivity of the aqueous solution was measured using an electrical conduction metre with automatic temperature compensation (Hanna instruments, DiST4). It was prepared by direct neutralization of aqueous tetrabutylphosphonium hydroxide solutions with trifluoroacetic acid.…”

“…[6][7][8][9][10][11][12] In particular, thermoresponsive phase behaviour of aqueous solutions of ILs has been extensively investigated in relation to phase transitions with lower critical solution temperatures (LCSTs) 6,12,13 as well as upper critical solution temperatures (UCSTs). 7 The chemical structure of [P 4444 ]CF 3 COO is shown in Fig. This transition is caused because the mixing entropic contribution in the mixing Gibbs energy generally becomes more dominant as the temperature (T) increases.…”