Aggregation Behavior of 1‑Dodecyl-3-methylimidazolium Bromide in Aqueous Solution: Effect of Ionic Liquids with Aromatic Anions

• Published in: Langmuir Vol. 29; no. 21; pp. 6213 - 6220
• Main Authors: Gu, Yingqiu, Shi, Lijuan, Cheng, Xiyuan, Lu, Fei, Zheng, Liqiang
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 28.05.2013
• Subjects: Anions - chemistry; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Hydrocarbons, Aromatic - chemistry; Imidazoles - chemistry; Ionic Liquids - chemistry; Micelles. Thin films; Molecular Structure; Particle Size; Solutions; Surface physical chemistry; Surface Tension; Surface-active agents: properties; Water - chemistry; Aggregation; Surface tension; Micellar critical concentration; Aqueous solution; Ionic liquid
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la400497r

The effects of ionic liquids (ILs), 1-butyl-3-methylimidazolium methylsulfonate (bmimMsa), 1-butyl-3-methylimidazolium benzenesulfonate (bmimBsa), and 1-butyl-3-methylimidazolium 2-naphthalenesulfonate (bmimNsa), on the aggregation behavior of 1-dodecyl-3-methylimidazolium bromide (C12mimBr) in aqueous solution were investigated by surface tension, dynamic light scattering measurements, and 1H NMR spectroscopy. The ability to promote the surfactant aggregation is in the order bmimNsa > bmimBsa > bmimMsa. Nevertheless, only bmimNsa distinctly reduces both the CMC value and the surface tension at CMC. Due to the penetration of C10H7SO3 – anions into the surfactant aggregate, bmimNsa is found to induce a phase transition from micelles to vesicles, whereas the other ILs only slightly increase the sizes of micelles. The combined effect of intermolecular interactions, such as hydrophobic effect, electrostatic attractions, and π–π stacking interactions, is supposed to be responsible for this structural transformation, in which π–π stacking plays an important role.