Size of sodium dodecyl sulfate micelles in the presence of additives. 2. Aromatic and saturated hydrocarbons

Almgren, Mats; Swarup, Shanti

doi:10.1021/j100218a024

Cited by 144 publications

(84 citation statements)

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“…Because of the rather poor inherent sensitivity of 13C NMR spectroscopy, Stark et al (14) used 100 mM solutions of nitrobenzene in 330 mM surfactant solutions. Such high concentrations of solubilizate may cause significant distortions in micellar structure since micelle size and shape are modified substantially by additives (19). From ' H NMR studies, Eriksson eta/.…”

Section: Introductionmentioning

confidence: 99%

NMR studies of hydrocarbons solubilized in aqueous micellar solutions

Wasylishen¹,

Kwak²,

Gao³

et al. 1991

Can. J. Chem.

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. 69, 822 (1991).Information concerning the solubilization of hydrocarbons in ionic surfactant micelles was obtained from 'H NMR relaxation, 'H NMR chemical shifts, and 'H NMR paramagnetic relaxation measurements. The rotational motion of deuterated hydrocarbons, which is related to the micellar microviscosity at the location of the hydrocarbons, was probed by ' H NMR relaxation. The relaxation data are interpreted using both the two-step and the single-step models, and the results are discussed in terms of the micellar microviscosity and the location of the hydrocarbons in micelles. The location of the hydrocarbons in micelles was further investigated by determining the aromatic ring current-induced 'H chemical shifts along the surfactant alkyl chain and by comparing the 'H spin-lattice relaxation enhancement of the hydrocarbons and the surfactant alkyl chain, induced by ~n ' ' on the micellar surface. The hydrocarbons used include benzene, naphthalene, acenaphthalene, triphenylene, cyclohexane, cyclododecane, and tert-butylcyclohexane and the surfactants studied are hexadecyl-, tetradecyl-, and dodecyltrimethylammonium bromide; hexadecyl-, tetradccyl-, and dodecylpyridinium halide; and sodium dodecyl sulfate. The results indicate that the micellar microviscosity at the location of saturated hydrocarbons is approximately 5 cP for both the cationic and anionic micelles, whereas the micellar microviscosity at the location of unsaturated hydrocarbons is much higher. The unsaturated hydrocarbons are found to reside primarily near the surfactant headgroup in the cationic micelles, but are distributed evenly throughout the anionic SDS micelles. The saturated hydrocarbons appear to be located in the interior of the micelles. 822 (1991). Utilisant la relaxation RMN du 'H, les dCplacements chimiques en RMN du 'H et des mesurcs de relaxation paramagnktique en RMN du 'H, on a obtenu de I'information concernant la solubilisation d'hydrocarbures dans des micelles d'agents de surfaceioniques. Pour Ctudier le mouvement de rotation des hydrocarbures deutCrCs qui est reliC la microviscositC micellaire au point de location des hydrocarbures, on a fait appel h la relaxation en RMN du 'H. On a interprCte les donnCes de relaxation utilisant les modkles en une ainsi qu'en deux Ctapes et on discute des rCsultats en fonction de la microviscositC micellaire et de la position des hydrocarbures dans les micelles. On a rCalisC une Ctude plus approfondie de I'influence de la position des hydrocarbures dans les micelles en determinant les dCplacements chimiques induits par le courant du noyau aromatique le long de la chaine alkyle de I'agent de surface et en comparant les augmentations des relaxations spin-reseau du 'H des hydrocarbures et de la chaine alkyle de I'agent de surface qui sont induites par du ~n ' .~ sur la surface micellairc. Les hydrocarbures utilisks sont le benzene, le naphtalkne, I'acCnaphtalkne, le triphknylkne, le cyclohexane, le cyclododCcane et le terl-butylcyclohexane alors que les agents de surface ttudiCs sont les ...

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Section: Introductionmentioning

confidence: 99%

NMR studies of hydrocarbons solubilized in aqueous micellar solutions

Wasylishen¹,

Kwak²,

Gao³

et al. 1991

Can. J. Chem.

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“…The aggregation number is also an important parameter which characterizes the self-association, since it is associated with the interracial free energy of micelles and is required for analysing the thermodynamics of micelle formation. Nevertheless, the aggregation number of mixed micelles has been addressed only in a few papers (Nakagawa & lnoue, 1957;Attwood, Elworthy & Kayne, 1971;Birdi, 1975;Almgren & Swarup, 1982, 1983a. The papers cited concern nonionic-nonionic and ionic-nonionic mixed micelles.…”

Section: Introductionmentioning

confidence: 99%

Small-angle neutron scattering study of sodium alkyl sulfate mixed micelles

et al. 1991

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Sodium (octyl + decyl) and (octyl + dodecyl) sulfate mixed surfactant solutions containing the two solutes in a 1:1 proportion were studied by small-angle neutron scattering. The measurements were carried out at different concentrations and temperatures. For mathematical reasons it was not possible to determine the composition of mixed micelles through a least-squares fitting procedure, and therefore Clint's theory assuming ideal mixing of the components was used to calculate the monomer concentrations and the composition of micelles. With the calculated composition, two-shell spherical and ellipsoidal shape models were fitted to the experimental scattering curves. Except for the (octyl + dodecyl) sulfate micelles at higher concentrations, the best fit was obtained by a spherical model. The aggregation number in the mixed systems obtained from the fit lies between the aggregation numbers of the two single-component constituent systems, but closer to that of the longer chain and shows strong concentration and temperature dependence. The fractional charge of the mixed micelles was found to be smaller than the fractional charge of the single-component ones.

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“…When surfactants are added to water at low concentration, they are dispersed as discrete molecules. However at a particular concentration, surfactant molecules get associated to form aggregates or micelles [12][13][14][15] . This concentration is known as critical micellar concentration (CMC) which is an important property of surfactant.…”

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confidence: 99%