Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003, USA.
Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003, USA.
J Colloid Interface Sci. 2016 Sep 1;477:40-5. doi: 10.1016/j.jcis.2016.05.020. Epub 2016 May 13.
The phase behavior of amphiphiles is known to depend on their solvent environment. The organic character of ionic liquids suggested the possibility to tune surfactant aggregation, even in the absence of water, by selection of appropriate ionic liquid chemistry. To that end the behavior of the surfactant sodium dodecylsulfate in a chemically similar imidazolium ionic liquid, 1-ethyl-3-methyl imidazolium ethylsulfate, was explored.
The solubility of sodium dodecylsulfate in 1-ethyl-3-methyl imidazolium ethylsulfate was determined, establishing the Krafft temperature. Tensiometry was performed to obtain interfacial properties such as the surface excess and area per molecule. Pulsed-field gradient spin-echo NMR was used to determine the diffusion coefficients of all the major species, including micelles, as a function of surfactant concentration. Importantly, all three methods provided consistent values for the critical micelle concentration.
Analysis of tensiometry data suggests, and is confirmed by NMR results, that the ionic liquid ions are incorporated along with surfactants into micelles, revealing a complex micellization behavior. In light of these findings past studies with ternary mixtures of surfactants, ionic liquids, and water may merit additional scrutiny. Given the large number of ionic liquids, this work suggests opportunities to further control micelle formation and properties.
众所周知，两亲物的相行为取决于其溶剂环境。离子液体的有机性质表明，通过选择合适的离子液体化学，可以在没有水的情况下调整表面活性剂的聚集，甚至可以调整表面活性剂的聚集。为此，探索了表面活性剂十二烷基硫酸钠在化学性质相似的咪唑离子液体 1-乙基-3-甲基咪唑硫酸乙酯中的行为。
确定了十二烷基硫酸钠在 1-乙基-3-甲基咪唑硫酸乙酯中的溶解度，确定了克拉夫特温度。张力法用于获得界面性质，如表面过剩和每个分子的面积。脉冲场梯度自旋回波 NMR 用于确定所有主要物质（包括胶束）的扩散系数，作为表面活性剂浓度的函数。重要的是，所有三种方法都为临界胶束浓度提供了一致的值。
张力法数据的分析表明，并且 NMR 结果证实，离子液体离子与表面活性剂一起掺入胶束中，揭示了复杂的胶束化行为。鉴于这些发现，过去关于表面活性剂、离子液体和水的三元混合物的研究可能值得进一步审查。鉴于离子液体的数量众多，这项工作为进一步控制胶束形成和性质提供了机会。
