Zwitterionic heterogemini surfactants containing ammonium and carboxylate headgroups 2: aggregation behavior studied by SANS, DLS, and cryo-TEM.
Zwitterionic heterogemini surfactants containing ammonium and carboxylate headgroups 2: aggregation behavior studied by SANS, DLS, and cryo-TEM.
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DOI：
10.1016/j.jcis.2011.12.027
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发表时间：
2012-03
影响因子：
9.9
通讯作者：
Kanae Nyuta;Tomokazu Yoshimura;K. Tsuchiya;H. Sakai;M. Abe;H. Iwase
中科院分区：
文献类型：
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作者：
Kanae Nyuta;Tomokazu Yoshimura;K. Tsuchiya;H. Sakai;M. Abe;H. Iwase
研究了两性异双子表面活性剂N，N-二甲基-N-[2-（2-甲氧基苯基）氨基]-N，N-二甲基-（N′-烷基-N ′-β-羧基丙酰氨基）乙基]-1-烷基溴化铵用小角中子散射（SANS）、动态光散射（DLS）、和低温透射电子显微镜（cryo-TEM）技术。我们发现2CnAmCa的聚集行为强烈依赖于烃链长度和表面活性剂浓度。2C 8AmCa在溶液中形成半径约为2nm的球形胶束。2C 10AmCa在低浓度时形成棒状胶束，随着浓度的增加，胶束结构逐渐转变为囊泡状。囊泡的膜厚度与表面活性剂浓度无关。还观察到2C 12 AmCa的聚集体形状转变。此外，它出现的囊泡2C 12 AmCa共存的棒状胶束在很宽的表面活性剂浓度范围内。有趣的是，2C 14 AmCa在溶液中形成平均膜厚度为2.32nm的囊泡，即使在10倍cmc的极低浓度下。结果表明，随着烃链长度和表面活性剂浓度的增加，2CnAmCa具有独特的聚集行为，如形成球形胶束→棒状胶束→棒状胶束+囊泡（共存）→囊泡。我们还发现，当囊泡形成时，膜结构是指状交叉的双层。这种叉指结构的形成与溶液中2CnAmCa的有效性质的起源有关。
The aggregation behavior in aqueous solution of zwitterionic heterogemini surfactants, N,N-dimethyl-N-[2-(N′-alkyl-N′-β-carboxypropanoylamino)ethyl]-1-alkylammonium bromides (2CnAmCa, in which n represents hydrocarbon chain lengths of 8, 10, 12, and 14), with nonidentical headgroups containing ammonium and carboxylate was investigated through small-angle neutron scattering (SANS), dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM) techniques. We found that the aggregation behavior of 2CnAmCa strongly depended on the hydrocarbon chain length and the surfactant concentration. 2C8AmCa forms spherical micelles with radius of approximately 2nm in solution. 2C10AmCa forms rod-like micelles at low concentration in the solution, and the structure changes to vesicles with increasing concentration. The membrane thickness of the vesicle is independent of the surfactant concentration. Aggregation shape transitions were also observed for 2C12AmCa. In addition, it appears that the vesicles of 2C12AmCa coexist with the rod-like micelles at a wide range of surfactant concentrations. Interestingly, 2C14AmCa forms vesicles with averaged membrane thickness of 2.32nm in solution, even at the extremely low concentration of 10 times the cmc. Thus, it was concluded that 2CnAmCa exhibits unique aggregation behavior, such as the formation of spherical micelle→rod-like micelle→rod-like micelle+vesicle (coexistence)→vesicle with increasing hydrocarbon chain length and surfactant concentration. We also found that the membrane structure is an interdigitated bilayer when the vesicles are formed. This formation of interdigitated structures is related to the origins of the effective properties of 2CnAmCa in solution.