Microemulsions with hydrophobic ionic liquids: Influence of the structure of the anion
Microemulsions with hydrophobic ionic liquids: Influence of the structure of the anion
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DOI：
10.1016/j.molliq.2016.12.014
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发表时间：
2017-02
影响因子：
6
通讯作者：
J. Porada;Markus Mansueto;S. Laschat;C. Stubenrauch
中科院分区：
文献类型：
--
作者：
J. Porada;Markus Mansueto;S. Laschat;C. Stubenrauch
离子液体（IL）的高极性通常会阻碍高效和强结构的水性微乳液的配制，其中IL应该取代疏水油相。克服该问题的一种策略是通过将脂肪族部分引入分子结构中来降低IL的极性。在以前的出版物中，我们证明了增加IL阳离子中辛基链的数量会降低极性：降低IL的极性，即疏水性化合物的极性，人们观察到微乳液的相行为遵循与常规微乳液相同的趋势。在手头的研究中，我们证明了当在IL的阴离子中引入烷基链时也是如此。为此，我们合成了一组三个离子液体与不同数量的辛基链的阴离子。我们研究了纯化合物以及二元和三元体系的相行为。在这些系统中的无氟离子液体微乳液的第一个例子。此外，一个代表性的三元体系的三个共存相的组成，确定了通过NMR方法。结果表明，与常规微乳液相比，极性的降低提高了体系的相变温度，拓宽了体系的三相区。增加IL中脂肪链的量的策略受到相变温度的增加的限制，这反过来又降低了效率。结果表明，这些微乳液的显着低效率可以归因于高溶解度的表面活性剂在IL中，这是最有可能引起的表面活性剂的环氧乙烷单元。
The high polarity of ionic liquids (ILs) often prevents the formulation of efficient and strongly structured aqueous microemulsions in which the IL is supposed to replace the hydrophobic oil phase. One strategy to overcome this problem is to reduce the polarity of the IL by introducing aliphatic moieties into the molecular structure. In a previous publication we demonstrated that increasing the number of octyl chains in thecationof the IL reduces the polarity: Decreasing the polarity of the IL, i.e. of the hydrophobic compound, one observes that the phase behavior of the microemulsion follows the same trends as the one known for conventional microemulsions. In the study at hand we demonstrate that the same holds true when alkyl chains are introduced in theanionof the IL. For this purpose we synthesized a set of three ILs with different numbers of octyl chains in the anion. We investigated the phase behavior of the pure compounds as well as of binary and ternary systems. Among these systems the first example of a fluorine-free IL microemulsion is presented. Additionally, the composition of the three coexisting phases of a representative ternary system was determined by an NMR method. It was found that, in analogy to conventional microemulsions, the reduction of the polarity increases the phase transition temperature and broadens the three-phase area of the system. The strategy of increasing the amount of aliphatic chains in the IL is limited by the increase in phase transition temperature, which, in turn, reduces the efficiency. It is shown that the remarkably low efficiency of these microemulsions can be attributed to the high solubility of the surfactant in the IL, which is most likely caused by the surfactant’s ethylene oxide units.