Kawai Risa, Yada Shiho, Yoshimura Tomokazu
Department of Chemistry, Faculty of Science, Nara Women's University, Kitauoyanishi-machi, Nara 630-8506, Japan.
Langmuir. 2021 Sep 28;37(38):11330-11337. doi: 10.1021/acs.langmuir.1c01912. Epub 2021 Sep 14.
The surface adsorption and aggregation behavior of a mixture of quaternary-ammonium-salt-type amphiphilic monomeric compounds (C FSA, C FSA, and C NTf) or gemini compounds (C-2-C FSA) and various surfactants (nonionic hexaoxyethylene dodecyl ether (CEO), anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethylammonium bromide (CTAB), and zwitterionic -dodecyl-,-dimethyl-3-ammonio-1-propanesulfonate (CSb)) was investigated. Both types of compounds contained alkyl chains of nonidentical lengths that used bis(fluorosulfonyl)imide (FSA) or bis(trifluoromethanesulfonyl)imide (NTf) as counterions. The mixtures were analyzed for surface tension, viscosity, electrical conductivity, and pyrene fluorescence, in addition to evaluation by cryogenic transmission electron microscopy, small-angle X-ray scattering, and dynamic light scattering. Our results showed that the surface tension depended on the surfactant structure. For the mixture of C FSA and SDS, as the SDS concentration increased, the surface tension first decreased and became constant at the critical micelle concentration (CMC). In this concentration range, C FSA and SDS were approximately equimolar (2.5 mmol dm), the mixture adsorbed efficiently at the air-water interface, and vesicles and linear-type micelles were formed in the solution owing to the decreased electrostatic repulsion between the hydrophilic groups. As the SDS concentration further increased, the surface tension increased and reached another constant value. The C FSA at the interface was replaced by SDS and the aggregates transformed into spherical micelles. The surface tension plot of the mixture of the amphiphilic compounds and CSb showed a minimum at the CMC. The lowest CMC and surface tension were observed for C-2-C FSA, indicating that the gemini compounds offer excellent adsorption and orientation at the air-water interface. It was revealed that the quaternary-ammonium-salt-type amphiphilic compounds in this study acted as ionic liquids on their own and as surfactants in aqueous solution. Further, they could improve the surface activity of conventional ionic surfactants.
研究了季铵盐型两亲单体化合物（C FSA、C FSA和C NTf）或双子化合物（C-2-C FSA）与各种表面活性剂（非离子型六氧乙烯十二烷基醚（CEO）、阴离子型十二烷基硫酸钠（SDS）、阳离子型十二烷基三甲基溴化铵（CTAB）和两性离子型十二烷基-N,N-二甲基-3-铵基-1-丙烷磺酸盐（CSb））混合物的表面吸附和聚集行为。这两类化合物都含有不同长度的烷基链，以双（氟磺酰）亚胺（FSA）或双（三氟甲磺酰）亚胺（NTf）作为抗衡离子。除了通过低温透射电子显微镜、小角X射线散射和动态光散射进行评估外，还对混合物进行了表面张力、粘度、电导率和芘荧光分析。我们的结果表明，表面张力取决于表面活性剂的结构。对于C FSA和SDS的混合物，随着SDS浓度的增加，表面张力首先降低，并在临界胶束浓度（CMC）时变得恒定。在此浓度范围内，C FSA和SDS近似等摩尔（2.5 mmol dm），混合物在空气-水界面有效吸附，并且由于亲水基团之间静电排斥力降低，在溶液中形成了囊泡和线性胶束。随着SDS浓度进一步增加，表面张力升高并达到另一个恒定值。界面处的C FSA被SDS取代，聚集体转变为球形胶束。两亲化合物与CSb混合物的表面张力曲线在CMC处出现最小值。对于C-2-C FSA观察到最低的CMC和表面张力，表明双子化合物在空气-水界面具有优异的吸附和取向性能。结果表明，本研究中的季铵盐型两亲化合物自身表现为离子液体，在水溶液中表现为表面活性剂。此外，它们可以提高传统离子表面活性剂的表面活性。
