LCST-type phase changes of a mixture of water and ionic liquids derived from amino acids
LCST-type phase changes of a mixture of water and ionic liquids derived from amino acids
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DOI：
10.1002/anie.200604402
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发表时间：
2007-01-01
影响因子：
16.6
通讯作者：
Ohno, Hiroyuki
中科院分区：
文献类型：
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作者：
Fukumoto, Kenta;Ohno, Hiroyuki
离子液体（Ionic Liquids，IL）[1]是一种在1008 ℃以下熔化的有机盐，特别是在室温下，具有可忽略的挥发性[2]和在很宽的温度范围内不可燃的特性。人们对具有针对特定应用而设计的官能团的离子液体越来越感兴趣。[3]人们已经在离子液体中研究了许多反应，大多数反应都像在普通分子液体中一样进行。离子液体与分子液体的协同作用也应该是显著的。测定了许多分子在IL/分子溶剂混合物中的分配系数。[4]混合物的可逆相控制在从反应开始到产物分离的过程中是重要的。已经报道了一些相分离行为，包括压力控制的IL/超临界CO2混合物[5]和温度驱动的IL/醇[6]和ILK 3 PO 4/水系统。[7]Seddon等人最近报道了一对不混溶的离子液体在加热时混合得到单相。[8]We先前已经从20种不同的氨基酸合成了IL，并研究了侧链的官能团对其物理化学性质的影响。[9]不溶于水的疏水性和手性离子液体也已通过氨基酸的化学修饰制备。[10]通过测量这些氨基酸衍生的IL在水中的溶解度，我们发现新制备的IL和水的混合物表现出独特的相行为。该混合物显示出具有较低临界溶解温度（LCST）的相分离。在某些聚合物溶液中发现了LCST型相分离。相反，离子液体如[bmim][BF 4]（bmim= 1-丁基-3-甲基咪唑）、[11]离子化合物和分子液体通常在临界溶解温度上显示相分离，因为这些化合物在水中的溶解度随温度增加而增加。很少有文献报道IL/分子液体混合物的LCST型相分离。[12]然而，LCST阶段
Ionic liquids (ILs)[1] are organic salts designed to melt below 1008C, in particular at room temperature, which have characteristic properties such as negligible volatility [2] and nonflammability over a wide temperature range. There is increasing interest in ILs that have functional groups designed for specific applications.[3] Many reactions have already been studied in ILs; most proceed as in ordinary molecular liquids. Cooperative action of ILs with molecular liquids should also be significant. The partition coefficients of many molecules in IL/molecular solvent mixtures have been determined.[4] Reversible phase control of the mixture is important in proceeding from the start of the reaction to the separation of products. Some phase-separation behavior has already been reported, including pressure-controlled IL/supercritical CO2 mixtures [5] and temperature-driven IL/alcohol [6] and ILK3PO4/water systems.[7] Seddon et al. recently reported that an immiscible pair of ILs mixed upon heating to give a monophase.[8]We have previously synthesized ILs from 20 different amino acids and studied the effect of functional groups of the side chain on their physicochemical properties.[9] Hydrophobic and chiral ILs that are insoluble in water have also been prepared by chemical modification of the amino acids.[10] By measuring the solubility of these amino acid derived ILs in water, we found that a mixture of newly prepared IL and water exhibited unique phase behavior. The mixture showed phase separation with a lower critical solution temperature (LCST). LCST-type phase separation has been found in some polymer solutions. Conversely, ILs such as [bmim][BF4](bmim= 1-butyl-3-methylimidazolium),[11] ionic compounds, and molecular liquids generally displayed phase separation with an upper critical solution temperature, because the solubility of these compounds in water increases with temperature. Few reports exist of LCST-type phase separation of IL/molecular liquid mixtures.[12] However, the LCST phase