Some ionic liquids (ILs) having moderate hydrophobicity show unique phase behavior after mixing them with water such as lower critical solution temperature (LCST)-type phase transition. Such IL/water mixtures are obtained as a homogeneous clear solution at a certain temperature, but it shows liquid/liquid phase separation after heating them up. From the viewpoint of water content, hydration degree of these ILs can be controlled by temperature. Even after the phase-separation, the IL phase still contains a considerable amount of water. This should be helpful in dissolving many materials including proteins. In this mini review, we introduce typical ILs to show this LCST-type phase transition to consider the requirements for component ions to show this transition. Also, we explain the way to control this thermoresponsibility. Some separation techniques are also shown as an application of this phase change.

一些具有中等疏水性的离子液体（IL）与水混合后会显示出独特的相态，例如较低的临界溶液温度（LCST）型相变。这样的IL /水混合物在一定温度下以均匀的澄清溶液形式获得，但加热后显示出液相/液相分离。从水分的观点出发，这些IL的水合度可以通过温度来控制。即使在相分离之后，IL相仍然包含大量的水。这将有助于溶解包括蛋白质在内的许多材料。在本篇微型综述中，我们介绍典型的离子液体以显示此LCST型相变，以考虑对组成离子的要求以显示该相变。另外，我们解释了控制这种热响应性的方法。