Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation
Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation
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DOI：
10.1039/b103275p
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发表时间：
2001-08-01
期刊：
影响因子：
9.8
通讯作者：
Rogers, RD
中科院分区：
文献类型：
--
作者：
Huddleston, JG;Visser, AE;Rogers, RD
制备了一系列亲水性和疏水性的1-烷基-3-甲基咪唑室温离子液体（RTILs），考察了烷基链长和阴离子对离子液体的水含量、密度、粘度、表面张力、熔点和热稳定性的影响。在这里研究的一系列RTIL中，阴离子的选择决定了水的可溶解性，并且对性能具有最显著的影响。亲水性阴离子（例如，氯化物和碘化物）产生与水以任何比例混溶的离子液体，但是在从溶液中除去一些水时，说明物理性质对水含量的变化是多么敏感。相比之下，对于含有更多疏水阴离子的离子液体（例如，PF（（6）-和N（SO_2CF_3）（2）（-））中，水分的去除对所得性能的影响较小。对于一系列1-烷基-3-甲基咪唑阳离子，随着烷基链长从丁基到己基再到辛基的增加，离子液体的疏水性增加，粘度增加，而密度和表面张力值降低。热分析表明，高温可达到之前的分解和DSC研究揭示了几个样品的玻璃化转变。将PF 6-离子液体已被用于从水中的有机分子的液/液分配和其中两个的结果也在这里讨论。值得注意的是，不应忽视离子液体的单个阳离子和阴离子的化学性质，因为在PF 6-离子液体的某些条件下，与水相接触可能导致PF 6-的缓慢水解，同时释放HF和其他物质。
A series of hydrophilic and hydrophobic 1-alkyl-3-methylimidazolium room temperature ionic liquids (RTILs) have been prepared and characterized to determine how water content, density, viscosity, surface tension, melting point, and thermal stability are affected by changes in alkyl chain length and anion. In the series of RTILs studied here, the choice of anion determines water miscibility and has the most dramatic effect on the properties. Hydrophilic anions (e.g., chloride and iodide) produce ionic liquids that are miscible in any proportion with water but, upon the removal of some water from the solution, illustrate how sensitive the physical properties are to a change in water content. In comparison, for ionic liquids containing more hydrophobic anions (e.g., PF((6)- and N(SO2CF3)(2)(-)), the removal of water has a smaller affect on the resulting properties. For a series of 1-alkyl-3-methylimidazolium cations, increasing the alkyl chain length from butyl to hexyl to octyl increases the hydrophobicity and the viscosities of the ionic liquids increase, whereas densities and surface tension values decrease. Thermal analyses indicate high temperatures are attainable prior to decomposition and DSC studies reveal a glass transition for several samples. ILs incorporating PF6- have been used in liquid/liquid partitioning of organic molecules from water and the results for two of these are also discussed here. On a cautionary note, the chemistry of the individual cations and anions of the ILs should not be overlooked as, in the case of certain conditions for PF6- ILs, contact with an aqueous phase may result in slow hydrolysis of the PF6- with the concomitant release of HF and other species.