Heat-induced phase separation of alkali chloride-HFIP-water mixtures

We have found that phase separation of alkali chloride-1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)-water ternary mixtures takes place by heating, although HFIP-water binary mixtures cannot be separated as the temperature rises up to the boiling point of HFIP. Phase separation of the ternary mixtures is induced on addition of alkali chloride (MCl) at lower temperature in the order of NaCl < LiCl < KCl. The change in the heterogeneity of MCl-HFIP-d1-D2O mixtures with rising temperature was observed using small-angle neutron scattering (SANS) technique. The temperature dependence of the hydrogen bonds of water-water and HFIP-water in MCl-HFIP-H2O mixtures was evaluated by means of infrared and NMR. According to the present results, the mechanism of heat-induced phase separation of MCl-HFIP-water mixtures has been discussed at the molecular level.