Aggregation Behavior of Brij-35/Perfluorononanoic Acid Mixtures

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• 作者：Mara Florencia Torres ; Pablo S. Sales ; Rita H. de Rossi ; Mariana A. Fernndez
• 刊名：Langmuir
• 出版年：2010
• 出版时间：December 7, 2010
• 年：2010
• 卷：26
• 期：23
• 页码：17858-17866
• 全文大小：971K
• 年卷期：v.26,no.23(December 7, 2010)
• ISSN：1520-5827

文摘

The mixed system of a nonionic hydrocarbon surfactant, polyoxyethylene (23) lauryl ether (Brij-35), and a perfluorinated surfactant, perfluorononanoic acid, was investigated by a combination of methods. The critical micelle concentrations (cmc’s) have been determined over a wide range of sample compositions by fluorescence and UV−visible spectrophotometry using pyrene and N-(4-nitrophenyl) perfluorononanamide, respectively, as molecular probes. The values of the cmc’s obtained were considerably different with the two techniques employed. Measurements of the ¹⁹F nuclear magnetic resonance chemical shift of the same mixtures showed two breaks in the plots of Δδ_f versus molar fraction of the perfluorinated surfactant. Conductivity and surface tension measurements also showed two breaks. The behavior is attributed to the formation of mixed micelles that change their composition when the fraction of the fluorinated compound increases and some segregation of the fluorinated compound takes place at a high total surfactant concentration.