Aggregation behavior of Brij-35/perfluorononanoic acid mixtures.
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 (19)F 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.
Instituto de Investigaciones en Físico-Química de Córdoba (INFIQC), Facultad de Ciencias Químicas, Departamento de Química Orgánica, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
María Florencia
MF
Torres
Pablo S
PS
Sales
Rita H
RH
de Rossi
Mariana A
MA
Fernández
D004553:Electric Conductivity; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008823:Micelles; D008956:Models, Chemical; D015335:Molecular Probes; D011092:Polyethylene Glycols / Q000737:chemistry*; D011721:Pyrenes / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013499:Surface Properties; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*
D008823:Micelles; D015335:Molecular Probes; D011721:Pyrenes; D013501:Surface-Active Agents; D011092:Polyethylene Glycols; C515901:Brij 35