Use of compounds exhibiting lower critical eutectic temperature type phase behavior

摘要

PROBLEM TO BE SOLVED: To provide a use as a temperature sensor or extraction medium of an ion liquid exhibiting LCST behavior and good in thermal stability.SOLUTION: Phosphonium salt represented by the formula (1) can be used as a temperature sensor with a lower limit critical solution temperature as an index in a mixture system with water as it exhibits phase separation behavior having the lower limit critical solution temperature with water and an extraction target can also used as a separation extraction medium by mixing with a water phase containing a separation extraction target and mutually dissolving/phase separating reversibly with temperature control. (1), where Rrepresents an alkyl group having 1 to 30 carbon atoms, Rrepresents an alkyl group or an alkoxy group having 1 to 30 carbon atoms, Rrepresents an alkyl group having 1 to 8 carbon atoms and n represents an integer of 1 to 4.SELECTED DRAWING: None