Sodium dodecyl sulfate, interactions with systems

Previously, the sodium dodecyl sulfate (SDS) surfactant system was also investigated with a 200 ps molecular dynamics computer simulation in the NVT-ensemble (7). In this computer simulation, the parameters of the atomic interaction potential functions were taken from the CHARMM force field. The calculations showed that the SDS micelle remains spherical with a radius of gyration in good agreement with the experimental results. Remarkable motions of the head-groups were observed and the trans to gauche populations are equivalent for the micelle and the analogous hydrocarbon, liquid dodecane. Recently, atomic-level studies of AOT reverse micelles and molecular dynamics simulations of the structure and dynamics of a dode-cylphosphocholine micelle in aqueous solution have been published (8, 9). 

Contact of surfactants with the skin and mucus membranes occurs either accidentally or as a consequence of normal use. Examples of this normal and everyday use are cleaning formulations, shampoos, foam baths, and toothpastes. Again this contact is seldom made with individual surfactants, in this case alcohol sulfates and alcohol ether sulfates, but through formulated products. It is known that surfactants present significant interactions, so that mixed systems are generally less aggressive than their individual components. However, the effect of pure surfactants merits attention, particularly sodium dodecyl sulfate, which is commonly used as a reference for many studies because of its high purity and availability. 

In this paper, we report the solution properties of sodium dodecyl sulfate (SDS)-alkyl poly(oxyethylene) ether (CjjPOEjj) mixed systems with addition of azo oil dyes (4-NH2, 4-OH). The 4-NH2 dye interacts with anionic surfactants such as SDS (11,12), while 4-OH dye Interacts with nonionic surfactants such as C jPOEn (13). However, 4-NH2 is dependent on the molecular characteristics of the nonionic surfactant in the anlonlc-nonlonic mixed surfactant systems, while in the case of 4-OH, the fading phenomena of the dye is observed in the solubilized solution. This fading rate is dependent on the molecular characteristics of nonionic surfactant as well as mixed micelle formation. We discuss the differences in solution properles of azo oil dyes in the different mixed surfactant systems. 

Various substances were added to formed coacervate systems to observe their effects. Added sodium dodecyl sulfate did not affect the coacervates. Microcrystalline cellulose particles, added to the coacervate system before and after the coacervates were formed, were observed to be too large to be incorporated in or interact with the coacervate drops. Coacervates made in glucose and sucrose solutions were unaffected by the sugar. 

In a study of phenacylphenylsulfone photolysis, CIDNP data were taken as evidence that the primary radical pairs cannot recombine to regenerate the starting material because the micelle forces a certain orientation of the radicals [63], From low-field 13C CIDNP and SNP measurements on cleavage of benzylic ketones in sodium dodecyl sulfate micelles, it was inferred [64] that the exchange interaction in these systems is several orders of magnitude smaller ( 10lorads 1 at a reduction distance of 6 A cf. the values in Section IV.B) and the distance dependence is much weaker (a x 0.5 A" cf. the discussion of Eq. 10) than generally assumed for radical pairs. By numerical solutions of the stochastic Liouville equation for a model of the micelle where one of the radicals is kept fixed at the center of the micelle while the other radical is allowed to diffuse, the results of MARY experiments, 13C CIDNP experiments at variable fields, and SNP experiments could be reproduced with the same set of parameters [65],... 

Bile salts are effective detergents because they contain both polar and nonpolar regions. They have several hydroxyl groups, all on one side of the ring system, and a polar side chain that allow interactions with water. The ring system itself is nonpolar and can interact with lipids or other nonpolar substances. Bile salts are planar, am-phipathic molecules, in contrast with such detergents as sodium dodecyl sulfate (text, p. 84), which are linear. 

Surfactant concentration (varied after polymerization) greatly affects the viscosity of associating polymer systems. Iliopoulos et al. studied the interactions between sodium dodecyl sulfate (SDS) and hydrophobically modified polyfsodium acrylate) with 1 or 3 mole percent of octadecyl side groups [85]. A viscosity maximum occurred at a surfactant concentration close to or lower than the critical micelle concentration (CMC). Viscosity increases of up to 5 orders of magnitude were observed. Glass et al. observed similar behavior with hydrophobically modified HEC polymers. [100] The low-shear viscosity of hydrophobically modified HEC showed a maximum at the CMC of sodium oleate. HEUR thickeners showed the same type of behavior with both anionic (SDS) and nonionic surfactants. At the critical micelle concentration, the micelles can effectively cross-link the associating polymer if more than one hydrophobe from different polymer chains is incorporated into a micelle. Above the CMC, the number of micelles per polymer-bound hydrophobe increases, and the micelles can no longer effectively cross-link the polymer. As a result, viscosity diminishes. 

Anionic Surfactants onto Kaolinite and lUite. In the investigation of the adsorption of sodium dodecylbenzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS) onto asphalt covered kaolinite and illite surfaces, Siffert et al. [5S] observed Langmuir type I isotherms for SDS adsorption onto Na kaolinite and Na illite while the SDBS exhibited a maximum in adsorption with a decrease beginning near the CMC. Adsorption maxima were observed near the CMC for both surfactants in the Ca kaolinite and Ca illite systems. The adsorption behavior was explained as precipitation of the calcium salt of the surfactants (an idea supported by other studies), and the interaction of the aromatic ring in SDBS with the asphalt. This interaction favors desorption of the asphalt rather than adsorption of the SDBS. The amount of asphalt desorbed by SDBS was twice that desorbed by SDS. Other explanations for adsorption maxima include mixed micelle formation [55] and electrostatic repulsion of micelles from the bdayer covered surface [59]. 

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