Effect of Counterions on the Shape, Hydration, and Degree of Order at the Interface of Cationic Micelles: the Triflate Case

Effect of Counterions on the Shape, Hydration, and Degree of Order at the Interface of Cationic Micelles: the Triflate Case

Author Lima, Filipe S. Google Scholar
Cuccovia, Iolanda M. Google Scholar
Horinek, Dominik Google Scholar
Amaral, Lia Q. Google Scholar
Riske, Karin A. Autor UNIFESP Google Scholar
Schreier, Shirley Google Scholar
Salinas, Roberto K. Google Scholar
Bastos, Erick L. Google Scholar
Pires, Paulo A. R. Google Scholar
Bozelli, Jose Carlos Google Scholar
Favaro, Denize C. Google Scholar
Rodrigues, Ana Clara B. Google Scholar
Dias, Luis Gustavo Google Scholar
El Seoud, Omar A. Google Scholar
Chaimovich, Hernan Google Scholar
Institution Universidade de São Paulo (USP)
Univ Regensburg
Universidade Federal de São Paulo (UNIFESP)
Universidade Federal do ABC (UFABC)
Abstract Specific ion effects in surfactant solutions affect the properties of micelles. Dodecyltrimethylammonium chloride (DTAC), bromide (DTAB), and methanesulfonate (DTAMs) micelles are typically spherical, but some organic anions can induce shape or phase transitions in DTA(+) micelles. Above a defined concentration, sodium triflate (NaTf induces a phase separation in dodecyltrimethylammonium triflate (DTATf micelles, a phenomenon rarely observed in cationic micelles. This unexpected behavior of the DTATf/NaTf system suggests that DTATf aggregates have unusual properties. the structural properties of DTATf micelles were analyzed by time-resolved fluorescence quenching, small-angle X-ray scattering, nuclear magnetic resonance, and electron paramagnetic resonance and compared with those of DTAC, DTAB, and DTAMs micelles. Compared to the other micelle types, the DTATf micelles had a higher average number of monomers per aggregate, an uncommon disk-like shape, smaller interfacial hydration, and restricted monomer chain mobility. Molecular dynamic simulations supported these observations. Even small water-soluble salts can profoundly affect micellar properties; our data demonstrate that the -CF3 group in Tf- was directly responsible for the observed shape changes by decreasing interfacial hydration and increasing the degree of order of the surfactant chains in the DTATf micelles.
Language English
Sponsor GENFIT program
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Instituto Nacional de Ciencia e Tecnologia de Fluidos Complexos (INCT-FCx)
Nucleo de Apoio a Pesquisa de Fluidos Complexos (NAP-FCx)
Grant number FAPESP: 2007/50970-5
FAPESP: 2008/50041-7
Date 2013-04-02
Published in Langmuir. Washington: Amer Chemical Soc, v. 29, n. 13, p. 4193-4203, 2013.
ISSN 0743-7463 (Sherpa/Romeo, impact factor)
Publisher Amer Chemical Soc
Extent 4193-4203
Origin http://dx.doi.org/10.1021/la304658e
Access rights Closed access
Type Article
Web of Science ID WOS:000317173300004
URI http://repositorio.unifesp.br/handle/11600/36194

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