Martín Victoria Isabel, Rodríguez Amalia, Laschewsky André, Moyá María Luisa
Department of Physical Chemistry, University of Seville, Profesor García González 1, 41012 Seville, Spain.
Institut für Chemie, Universitat Postdam, Karl-Liebknecht Str. 25, 14476 Postdam-Golm, Germany; Fraunhofer Institute of Applied Polymer Research, Geiselbergstr. 69, 14476 Postdam-Golm, Germany.
J Colloid Interface Sci. 2014 Sep 15;430:326-36. doi: 10.1016/j.jcis.2014.05.064. Epub 2014 Jun 10.
The micellization of four dimeric cationic surfactants ("gemini surfactants") derived from N-dodecyl-N,N,N-trimethylammonium chloride was studied in pure water and in water-ionic liquid (IL) solutions by a wide range of techniques. The dimeric surfactants are distinguished by their rigid spacer groups separating the two surfactant motifs, which range from C3 to C5 in length. In order to minimize organic ion pairing effects as well as the role of the ionic liquids as potential co-surfactants, ILs with inorganic hydrophilic anions and organic cations of limited hydrophobicity were chosen, namely ethyl, butyl, and hexyl-3-imidazolium chlorides. (1)H NMR two-dimensional, 2D, rotating frame nuclear Overhauser effect spectroscopy measurements, ROESY, supported this premise. The spacer nature hardly affects the micellization process, neither in water nor in water-IL solutions. However, it does influence the tendency of the dimeric surfactants to form elongated micelles when surfactant concentration increases. In order to have a better understanding of the ternary water-IL surfactant systems, the micellization of the surfactants was also studied in aqueous NaCl solutions, in water-ethylene glycol and in water-formamide binary mixtures. The combined results show that the ionic liquids play a double role in the mixed systems, operating simultaneously as background electrolytes and as polar organic solvents. The IL role as organic co-solvent becomes more dominant when its concentration increases, and when the IL alkyl chain length augments.
通过多种技术研究了由N-十二烷基-N,N,N-三甲基氯化铵衍生的四种二聚阳离子表面活性剂（“双子表面活性剂”）在纯水以及水-离子液体（IL）溶液中的胶束化作用。这些二聚表面活性剂的区别在于连接两个表面活性剂结构单元的刚性间隔基团，其长度范围从C3到C5。为了尽量减少有机离子对效应以及离子液体作为潜在助表面活性剂的作用，选择了具有无机亲水性阴离子和疏水性有限的有机阳离子的离子液体，即乙基、丁基和己基-3-咪唑鎓氯化物。核磁共振氢谱二维（2D）旋转框架核Overhauser效应光谱测量（ROESY）支持了这一前提。间隔基团的性质对胶束化过程几乎没有影响，无论是在水中还是在水-离子液体溶液中。然而，当表面活性剂浓度增加时，它确实会影响二聚表面活性剂形成细长胶束的趋势。为了更好地理解三元水-离子液体-表面活性剂体系，还研究了表面活性剂在NaCl水溶液、水-乙二醇和水-甲酰胺二元混合物中的胶束化作用。综合结果表明，离子液体在混合体系中起双重作用，同时作为背景电解质和极性有机溶剂。当离子液体的浓度增加以及其烷基链长度增加时，其作为有机共溶剂的作用变得更加显著。
