Molecular Conformation-Controlled Vesicle/Micelle Transition of Cationic Trimeric Surfactants in Aqueous Solution

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• 作者：Chunxian Wu ; Yanbo Hou ; Manli Deng ; Xu Huang ; Defeng Yu ; Junfeng Xiang ; Yu Liu ; Zhibo Li ; Yilin Wang
• 刊名：Langmuir
• 出版年：2010
• 出版时间：June 1, 2010
• 年：2010
• 卷：26
• 期：11
• 页码：7922-7927
• 全文大小：876K
• 年卷期：v.26,no.11(June 1, 2010)
• ISSN：1520-5827

文摘

Two star-like trimeric cationic surfactants with amide groups in spacers, tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD) and tri(dodecyldimethylammonioacetoxy)tris(2-aminoethyl)amine trichloride (DDAD), have been synthesized, and the aggregation behavior of the surfactants in aqueous solution has been investigated by surface tension, electrical conductivity, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, and NMR techniques. Typically, both the surfactants form vesicles just above critical aggregation concentration (CAC), and then the vesicles transfer to micelles gradually with an increase of the surfactant concentration. It is approved that the conformation of the surfactant molecules changes in this transition process. Just above the CAC, the hydrophobic chains of the surfactant molecules pack more loosely because of the rigid spacer and intramolecular electrostatic repulsion in the three-charged headgroup. With the increase of the surfactant concentration, hydrophobic interaction becomes strong enough to pack the hydrophobic tails tightly and turn the molecular conformation into a pyramid-like shape, thus leading to the vesicle to micelle transition.