Molecular Aggregates of Partially Fluorinated Quaternary Ammonium Salt Gemini Surfactants

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• 作者：Keisuke Matsuoka ; Tomokazu Yoshimura ; Takashi Shikimoto ; Juri Hamada ; Mika Yamawaki ; Chikako Honda ; Kazutoyo Endo
• 刊名：Langmuir
• 出版年：2007
• 出版时间：October 23, 2007
• 年：2007
• 卷：23
• 期：22
• 页码：10990 - 10994
• 全文大小：264K
• 年卷期：v.23,no.22(October 23, 2007)
• ISSN：1520-5827

文摘

The size and shape of novel partially fluorinated gemini surfactant 1,2-bis[dimethyl-(3-perfluoroalkyl-2-hydroxypropyl)ammonium]ethane bromide (C_n^FC₃-2-C₃C_n^F, where n = 4, 6, and 8) were investigated in aqueoussolution by means of light scattering and transmission electron microscopy (TEM). The sizes of these molecularaggregates changed with increasing carbon number of the alkyl chain and concentration. For example, the apparenthydrodynamic radius by dynamic light scattering was 18 nm at a concentration of cmc × 5 for n = 4, 115 nm at thecmc × 15 for n = 6, and 62 nm at the cmc × 30 for n = 8, at 298.2 K. The shapes of C_n^FC₃-2-C₃C_n^F aggregatesdrastically changed with the alkyl chain length; the aggregates were mainly in the form of large or irregular smallaggregates (n = 4), string-like aggregates (n = 6), and vesicles (n = 8). The bromide-ion activity was measured usinga bromide-ion-selective electrode to determine the degree of counterion binding to the aggregates. The degree ofcounterion binding to aggregate was very small compared with that in the typical hydrogenated gemini surfactants.These results indicated that the small curvature of large aggregates was not influenced by an electrostatic repulsionbetween the cationic head groups in the case of the bulky molecular volume of fluorinated gemini surfactants.