Effect of Functional Group on the Monolayer Structures of Biodegradable Quaternary Ammonium Surfactants

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• 作者：Aimin Ge ; Qiling Peng ; HengLiang Wu ; Huijin Liu ; Yujin Tong ; Takuma Nishida ; Naoya Yoshida ; Keigo Suzuki ; Takaya Sakai ; Masatoshi Osawa ; Shen Ye
• 刊名：Langmuir
• 出版年：2013
• 出版时间：November 26, 2013
• 年：2013
• 卷：29
• 期：47
• 页码：14411-14420
• 全文大小：516K
• 年卷期：v.29,no.47(November 26, 2013)
• ISSN：1520-5827

文摘

The monolayer structures and conformational ordering of cationic surfactants including the biodegradable quaternary ammonium molecules have been systematically characterized by 蟺鈥?i>A isotherm, surface potential, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and sum frequency generation (SFG) vibrational spectroscopy. It was found that the monolayer of the typical dialkyl dimethylammonium on the water surface was less densely packed along with many conformational gauche defects. The packing density and ordering of these monolayers were improved as halide ions were added to the subphase. A similar condensation effect was also observed when amide or ester groups are present in the alkyl tails of the surfactant. These results are discussed on the basis of the repulsive electrostatic interactions between the terminal ammonium moieties, the hydrogen bonding between the functional groups in the alkyl chains, as well as the flexibility of the alkyl chains in these surfactants. The present study is crucial to understanding the relationship between the interfacial structures and the functionalities of the biodegradable quaternary ammonium surfactants.