Li Na, Zhang Shaohua, Zheng Liqiang, Inoue Tohru
Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, China.
Langmuir. 2009 Sep 15;25(18):10473-82. doi: 10.1021/la901170j.
The cationic fluorinated surfactant, FC-4, unlike other surfactants, forms micelles in the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (bmimTf2N). Surface tension, freeze-fracture transmission electron microscopy, 19F NMR, 1H NMR, and Fourier transform infrared measurements revealed that (i) the FC-4 cation forms an ion pair with the Tf2N anion, (ii) the ion pairs undergo association to form premicellar aggregates, and (iii) the premicellar aggregates transform into micelles at the critical micelle concentration (CMC). The thermodynamic parameters for micelle formation derived from the temperature dependence of the CMC demonstrated that the solvophobic interaction between the solvophobic tails of the surfactant molecules is rather weak in bmimTf2N compared with other ionic liquids, in accordance with the observation that surfactants do not readily form micelles in bmimTf2N. The fact that FC-4 forms micelles in such an inconvenient solvent is attributed to the ion-pair formation between the surfactant cation and the ionic liquid anion.
与其他表面活性剂不同，阳离子氟化表面活性剂FC - 4能在室温离子液体1 - 丁基 - 3 - 甲基咪唑双（三氟甲基磺酰）亚胺（bmimTf2N）中形成胶束。表面张力、冷冻断裂透射电子显微镜、19F核磁共振、1H核磁共振和傅里叶变换红外测量结果表明：（i）FC - 4阳离子与Tf2N阴离子形成离子对；（ii）离子对发生缔合形成前胶束聚集体；（iii）前胶束聚集体在临界胶束浓度（CMC）时转变为胶束。由CMC的温度依赖性得出的胶束形成热力学参数表明，与其他离子液体相比，表面活性剂分子的疏溶剂尾部之间的疏溶剂相互作用在bmimTf2N中相当弱，这与表面活性剂在bmimTf2N中不易形成胶束的观察结果一致。FC - 4能在这种不太适宜的溶剂中形成胶束这一事实归因于表面活性剂阳离子与离子液体阴离子之间形成了离子对。
