Micelle dodecyl ether sulfate

Fig. 4 Degree of dissociation (a) of dodecyl ether sulfate micelles...

It was concluded from measurements of sedimentation, diffusion, and viscosity, that the hydration of the micelles of the dodecyl ether sulfates at m = 0 - 2 shows only a little increase, whereas a strong one was observed at m > 2. A similar trend should also exist with the distance of the terminal groups on the surface of the micelles. 

Sanchez et al. [61,62] studied the stability of sodium decyl, dodecyl, and tetradecyl sulfates and sodium lauryl ether (3 EO) sulfate in acid media (pH 1) at different temperatures and concentrations above and below the critical micelle concentration. Sodium decyl sulfate was shown to be relatively stable for several hours at temperatures up to 90°C. Sodium dodecyl and tetradecyl sulfates were only stable for short periods of time at temperatures above 40-50°C. As expected, sodium lauryl ether sulfate was less stable to hydrolysis than the corresponding lauryl sulfate. 

Figure 5.2. Variance of aggregation number distribution of micelles (Nf - JVj) of pen-taoxyethylene dodecyl ether (C12E5) and hexaoxyethylene dodecyl sulfate (C12E6) at 298.15 K as a function of total surfactant concentration (Ci) under various pressures. A, 0.1 MPa B, 20 MPa C, 40 MPa D, 100 MPa E. 160 MPa. (Reproduced with permission of the American Chemical Society.)...

Another relatively new lipophilicity scale proposed for use in ADME studies is based on MEKC [106]. A further variant is called BMC and uses mobile phases of Brij35 [polyoxyethylene(23)lauryl ether] [129]. Similarly, the retention factors of 16 P-blockers obtained with micellar chromatography with sodium dodecyl sulfate as micelle-forming agent correlates well with permeability coefficients in Caco-2 monolayers and apparent permeability coefficients in rat intestinal segments [130]. 

It has been found that the combination of Lewis acids and surfactants is particularly effective for catalyzing Diels-Alder reactions in water. The effect of micelles of SDS, CTAB, dodecyl heptaoxyethy-lene ether (Q2E7), and copper and zinc didodecyl sulfate [M(DSb] on the Diels-Alder reaction of 3-(p-substituted phenyl)- l-(2-pyridyl)-2-propen-l-ones (Figure 12.1) with cyclopentadiene was studied. 

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. 

Even greater rates have been achieved in the Yb(OTf)3-catalysed aldol reactions of silylenol ethers with aldehydes in micelles, by adding a small quantity of surfactant, such as sodium dodecyl sulfate. 

Micelles and cyclodextrins are the most common reagents used for this technique. Micellar electrokinetic capillary chromatography (MECC or MEKC) is generally used for the separation of small molecules [6], Sodium dodecyl sulfate at concentrations from 20 to 150 mM in conjunction with 20 mM borate buffer (pH 9.3) or phosphate buffer (pH 7.0) represent the most common operating conditions. The mechanism of separation is related to reversed-phase liquid chromatography, at least for neutral solutes. Organic solvents such as 5-20% methanol or acetonitrile are useful to modify selectivity when there is too much retention in the system. Alternative surfactants such as bile salts (sodium cholate), cationic surfactants (cetyltrimethy-lammonium bromide), nonionic surfactants (poly-oxyethylene-23-lauryl ether), and alkyl glucosides can be used as well. 

Polysaccharides with Surfactant Micelles. Consider a solution of a fairly hydrophobic polysaccharide, such as a cellulose ether. The hydrophobic groups cause a weak attractive interaction, leading to a somewhat increased viscosity at low shear rates. If an anionic small-molecule surfactant is added, say SDS (sodium dodecyl sulfate), at a concentration above the CMC (critical micellization concentration), micelles are formed that interact with the polymer more specifically, one or a few polymer chains can pass through a micelle. In this way, polymer chains can be cross-linked. If now the polymer concentration c is below c (the chain overlap concentration), mainly intramolecular junctions are formed. If c > c, however, a gel results. In this manner, viscoelastic gels can be made with a modulus of the order of 10 Pa. 

HASE (hydrophobically modified alkali-swellable emulsion, discussed in Chapters 25 and 28) and HEUR thickeners are readily displaced from acrylic latex surfaces (32) by sodium dodecyl sulfate (SDS). A surface-active cellulose ether was also reported (33) to desorb from monodispersed poly(styrene) latices with SDS addition. In these studies, the relative critical micelle concentrations of the anionic surfactant and thickener appear to be more important than buffering of surface charges. 

Recently, Kobayashi noticed that the presence of a small amount of a surfactant such as sodium dodecyl sulfate (SDS) showed a remarkable enhancement of the reactivity in the Mukaiyama-catalyzed aldol reaction in pure water using Yb(OTf)3 or better Sc(OTf )3 as the catalyst without addition of the surfactant, the reaction was very sluggish (Scheme 8.4). Other surfactants such as calix[6]arene derivatives bearing sulfonate and alkyl groups or aromatic and aliphatic anionic surfactants have also been found to be highly effective in the aqueous Mukaiyama aldol reactions in pure water, affording the aldol products in high yields. This was probably due to the formation of micelles which stabilized the labile silyl enol ethers and thus promoted the aldol reaction. 

In a pioneering study, Nakamura et al. have pointed out enhancement of photochemical dimerization of ACN in micelles compared to dimerization in solution phase.They employed sodium dodecyl sulfate (SDS) as an ionic surfactant and polyoxyethylene-polyoxypropylene cetyl ether (PBC-34) as a nonionic surfactant. In general, the dimerization occurred efficiently in both of the micelles even with concentrations of ACN as low as 1.9 mmol, whereas dimerization in benzene solution was nil. Under concentrations of 5 30 mmol of ACN, the cisoid/transoid ratio in PBC-30 was ca. 0.8 and independent on the initial concentration of ACN, while that in SDS was as high as 2.7, showing dependence of the ratio on the surfactant used. 

Kriegel et al. [165] again found that the addition of PEO (25% of polymer content) facilitated fiber formation from chitosan. They included in the blend fibers different surfactants, i.e. sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB) and polyoxyethylene glycol (23) lauryl ether (Brij 35). The surfactants can be retained in the nanofibers either in the form of micelles or monomers. Furthermore, the addition of... 

Matsubara, H., Muroi, S., Kameda, M., Ikeda, N., Ohta, A., Aratono, M. Interaction between ionic and nonionic surfactants in the adsorbed film and micelle. 3. Sodium dodecyl sulfate and tetraethylene glycol monooctyl ether. Lanemuir 2fifi, 77(25), 7752-7757. 

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