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Titolo:
Dielectric relaxation behavior of cationic micellar solutions: 2
Autore:
Imai, S; Shiokawa, M; Shikata, T;
Indirizzi:
Osaka Univ, Dept Macromol Sci, Toyonaka, Osaka 5600043, Japan Osaka Univ Toyonaka Osaka Japan 5600043 i, Toyonaka, Osaka 5600043, Japan
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 19, volume: 105, anno: 2001,
pagine: 4495 - 4502
SICI:
1520-6106(20010517)105:19<4495:DRBOCM>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
THREAD-LIKE MICELLES; CETYLTRIMETHYLAMMONIUM BROMIDE; SURFACTANTS; MOTION; WATER;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
27
Recensione:
Indirizzi per estratti:
Indirizzo: Shikata, T Osaka Univ, Dept Macromol Sci, Toyonaka, Osaka 5600043, Japan Osaka Univ Toyonaka Osaka Japan 5600043 , Osaka 5600043, Japan
Citazione:
S. Imai et al., "Dielectric relaxation behavior of cationic micellar solutions: 2", J PHYS CH B, 105(19), 2001, pp. 4495-4502

Abstract

Dielectric relaxation behavior was examined, in the frequency range from 1MHz to 20 GHz, for an aqueous micellar system of cetyltrimethylammonium bromide (CTAB) with the concentration (Co) from 2 to 1000 m mol kg(-1). The system exhibited three dielectric relaxation modes. The fastest mode, with arelaxation time around 1 ns, had relaxation strength proportional to CD upto CD values of 100 m mo kg(-1), and showed a constant relaxation strengthindependent of CD above that concentration. The fastest relaxation mode attributed to the rotational relaxation mode of ionic pairs formed between CTA(+) and Br- in spherical micelles is considerably depressed in contact areas on the micellar surface of two micelles in contact with each other at CDvalues higher than 100 m mol kg(-1). This is likely the reason for the leveling-off in the magnitude of the fastest relaxation at high CD and the appearance of the slowest relaxation mode, which has a relaxation time of about 20 ns and increases in strength with increasing CD. The intermediate relaxation mode (with a relaxation time around 8 ns, and strength which decreases with increasing with CD) is attributed to the migration of electrically bound Br- ions around spherical micelles. The average number of Br- ions bound into an ionic cloud covering a micelle was estimated to be less than unity (from the values of direct current electric conductance and Br- concentration determined by use of a Br- selective ion electrode), and a small number of micelles possessed ionic clouds which showed dielectric relaxation behavior.

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Documento generato il 19/01/20 alle ore 21:10:42