Controlling the Morphology of Membranes by Excess Surface Charge in Cat鈥揂nionic Fluorinated Surfactant Mixtures

详细信息    查看全文

• 作者：Yuwen Shen ; Zhong-can Ou-Yang ; Yufeng Zhang ; Jingcheng Hao ; Zhaohui Liu
• 刊名：Langmuir
• 出版年：2014
• 出版时间：March 18, 2014
• 年：2014
• 卷：30
• 期：10
• 页码：2632-2638
• 全文大小：409K
• 年卷期：v.30,no.10(March 18, 2014)
• ISSN：1520-5827

文摘

The segregation and phase sequence of semifluorinated cat鈥揳nionic surfactant membranes at different excess surface charges was investigated by freeze-fracture transmission electron microscope (FF-TEM), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR). The thermal behavior of the membranes was evaluated by conductivity, rheology, and deuterium nuclear magnetic resonance (²H NMR). The experimental results show that the cat鈥揳nionic fluorinated surfactant mixtures can form faceted vesicles and punctured lamellar phase when there is excess surface charge. The cationic and anionic fluorinated surfactants are stiff in the membranes, like phospholipids in the frozen 鈥渃rystalline鈥?or 鈥済el鈥?phase. For the system with excess cationic surface charge, the gel-like faceted vesicles and punctured lamellae can transform into smooth-shaped vesicles at 65 掳C. However, for the system with no excess charge or with excess anionic surface charge, no phase transformation occurs even at 90 掳C. A model was established to demonstrate the mechanism of the formation and transition of the aggregates with different morphologies. The segregation鈥揷rystallization mechanism works well with other cosmotropic counterions from the Hofmeister series. The observations provide a better understanding of how to control the membrane morphology of the aqueous solutions of cat鈥揳nionic surfactant mixtures.