Micelle sulfates

Detergents are substances including soaps that cleanse by micellar action A large number of synthetic detergents are known One example is sodium lauryl sulfate Sodium lauryl sulfate has a long hydrocarbon chain terminating m a polar sulfate ion and forms soap like micelles m water... 

Detergents are designed to be effective in hard water meaning water containing calcium salts that form insoluble calcium carboxylates with soaps These precipitates rob the soap of Its cleansing power and form an unpleasant scum The calcium salts of synthetic deter gents such as sodium lauryl sulfate however are soluble and retain their micelle forming ability even m hard water... 

For the investigation of molecular recognition in micelles, adenine derivatives and positively charged (thyminylalkyl)ammonium salts such as shown in Figure 30 were prepared, which were solubilized in sodium dodecyl sulfate (SDS) solutions. Nmr studies have shown that binding occurs in a 1 1 molar ratio in the interior of the micelles as illustrated in Figure 30 (192). 

MeutralSoluble Salts. So dium sulfate [7757-82-6] and, to a considerably lesser extent, sodium chloride [7647-14-5] are the principal neutral soluble salts used in laundering compositions. They are often considered to be fillers although they perform an important standardizing function enabling the formulator to manufacture powders of a desired, controlled density. Sodium sulfate, in addition, lowers the critical micelle concentration of organic surfactants and thus the concentration at which effective washing can be achieved. 

In some cases, due to the highly polar character of the sulfate radicals, peroxydisulfate initiators can provide slow polymerization rates with some apolar monomers since the polar sulfate radicals cannot easily penetrate into the swollen micelle structures containing apolar monomers. The use of mercaptans together with the peroxydisulfate type initiators is another method to obtain higher polymerization rates [43]. The mercaptyl radicals are more apolar relative to the free sulfate radicals and can easily interact with the apolar monomers to provide higher polymerization rates. 

Water is extensively used to produce emulsion polymers with a sodium stearate emulsifrer. The emulsion concentration should allow micelles of large surface areas to form. The micelles absorb the monomer molecules activated by an initiator (such as a sulfate ion radical 80 4 ). X-ray and light scattering techniques show that the micelles start to increase in size by absorbing the macromolecules. For example, in the free radical polymerization of styrene, the micelles increased to 250 times their original size. 

Sodium dodecyl sulfate micelle 71,72,77,79 Spin label 139 Starch 100, 104 —, crosslinked 106 —, graft polymers 105, 107, 125, 127 Styrene 160—162 Styrene-divinylbenzene resins 167 Styrenesulfonic acid, copolymers 74—76 Surface area 147... 

If the coupling component is not ionic, however, more dramatic effects occur, as found by Hashida et al. (1979) and by Tentorio et al. (1985). Hashida used N,N-bis(2-hydroxyethyl)aniline, while Tentorio and coworkers took 1-naphthylamine and l-amino-2-methylnaphthalene as coupling components. With cationic arenediazo-nium salts and addition of sodium dodecyl sulfate (SDS), rate increases up to 1100-fold were measured in cases where the surfactant concentration was higher than the critical micelle concentration (cmc). Under the same conditions the reaction... 

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. 

The heats of dilution of sodium dodecyl sulfate in 0.0001 M NaCl and 0.145 M NaCl solutions have been determined in a study of the thermodynamics of the reaction with cetylpyridinium chloride. The heat of dilution includes the heat of dilution of the monomer, the heat of micellization, and the heat of dilution of the micelle [71]. 

The curve shown in Fig. 6 for sodium dodecyl sulfate is characteristic of ionic surfactants, which present a discontinuous and sharp increase of solubility at a particular temperature [80]. This temperature is known as the Krafft temperature. The Krafft temperature is defined by ISO as the temperature [in practice, a narrow range of temperatures] at which the solubility of ionic surface active agents rises sharply. At this temperature the solubility becomes equal to the critical micelle concentration (cmc). The curve of solubility vs. temperature intersects with the curve of the CMC vs. temperature at the Krafft temperature. 

TABLE 14 Critical Micelle Concentrations of Alcohol Sulfates... 

Shedlovsky et al. studied mixtures of sodium decyl, dodecyl, and tetradecyl sulfates by electromotive force measurements and determined the extent of the dissociation of the sodium counterions by the micelles. From the data obtained strong interaction below the CMC was found for all of the mixtures except those containing more than 25 mol % of sodium decyl sulfate [122]. Commercial alcohol sulfates are mixtures of homologs with different hydrocarbon chains. It has been demonstrated [123] that the CMC of such products is lower than that expected by calculation from the linear relationship between log CMC and the number of carbon atoms of the alcohol as stated in Eq. (11). These results are shown in Fig. 9. 

Table 17 shows the CMCs of sodium alcohol propoxysulfates at 20°C determined from surface tension measurements by the maximum bubble pressure [127] and Table 18 shows the critical micelle concentrations of sodium pro-poxylated octylphenol and propoxylated nonylphenol sulfates. Surface tension... 

The logarithm of the micellar molecular weight (M) and consequently the aggregation number of sodium dodecyl sulfate at 25°C in aqueous sodium chloride solutions is linearly related to the logarithm of the CMC plus the concentration of salt (Cs), both expressed in molar units, through two equations [116]. Below 0.45 M NaCl micelles are spherical or globular, and Eq. (18) applies ... 

The conductivity of sodium dodecyl sulfate in aqueous solution and in sodium chloride solutions was studied by Williams et al. [98] to determine the CMC. Goddard and Benson [146] studied the electrical conductivity of aqueous solutions of sodium octyl, decyl, and dodecyl sulfates over concentration ranges about the respective CMC and at temperatures from 10°C to 55°C. Figure 14 shows the results obtained by Goddard and Benson for the specific conductivity of sodium dodecyl sulfate and Table 25 shows the coefficients a and p of the linear equation of the specific conductivity, in mho/cm, vs. the molality of the solution at 25°C. Micellization parameters have been studied in detail from conductivity data in a recent work of Shanks and Franses [147]. 

The conformation of [34-65] bacterioopsin polypeptide incorporated into perdeuterated sodium dodecyl sulfate micelles in the presence of trifluoroethanol was investigated by nuclear magnetic resonance (NMR) [184],... 

Sodium dodecyl sulfate and hydrogen dodecyl sulfate have been used as catalysts in the denitrosation iV-nitroso-iV-methyl-p-toluenesulfonamide [138]. The kinetics of condensation of benzidine and p-anisidine with p-dimethylamino-benzaldehyde was studied by spectrophotometry in the presence of micelles of sodium dodecyl sulfate, with the result that the surfactant increases the rate of reaction [188]. The kinetics of reversible complexation of Ni(II) and Fe(III) with oxalatopentaaminecobalt(III) has been investigated in aqueous micellar medium of sodium dodecyl sulfate. The reaction occurs exclusively on the micellar surface [189]. Vitamin E reacts rapidly with the peroxidized linoleic acid present in linoleic acid in micellar sodium dodecyl sulfate solutions, whereas no significant reaction occurs in ethanol solution [190]. 

Mechanisms of micellar reactions have been studied by a kinetic study of the state of the proton at the surface of dodecyl sulfate micelles [191]. Surface diffusion constants of Ni(II) on a sodium dodecyl sulfate micelle were studied by electron spin resonance (ESR). The lateral diffusion constant of Ni(II) was found to be three orders of magnitude less than that in ordinary aqueous solutions [192]. Migration and self-diffusion coefficients of divalent counterions in micellar solutions containing monovalent counterions were studied for solutions of Be2+ in lithium dodecyl sulfate and for solutions of Ca2+ in sodium dodecyl sulfate [193]. The structural disposition of the porphyrin complex and the conformation of the surfactant molecules inside the micellar cavity was studied by NMR on aqueous sodium dodecyl sulfate micelles [194]. 

From experience in metalworking applications it is known that ether carboxylates may improve the existing corrosion protection of formulations [66]. From pKj studies described by Aalbers [49], an internal neutralization of the ether carboxylate micelles can be concluded resulting in less anionic character than, for example, alkyl sulfates therefore also combination with quats are possible without any problem. 

It has been found that the CMC values are higher and the micelle aggregation numbers smaller than those of the corresponding nonionic surfactants. The CMC increases with increasing EO chain, which is, according to the authors, opposite to the results for sodium alkyl ether sulfate. 

Compared with sodium w-alkyl sulfates the ester sulfonates with the same number of carbon atoms in the hydrophobic chain have lower CMC values because the methyl group also contributes to the micellization. 

Fujiwara et al. used the CMC values of sodium and calcium salts to calculate the energetic parameters of the micellization [61]. The cohesive energy change in micelle formation of the a-sulfonated fatty acid methyl esters, calculated from the dependency of the CMC on the numbers of C atoms, is equivalent to that of typical ionic surfactants (Na ester sulfonates, 1.1 kT Ca ester sulfonates, 0.93 kT Na dodecyl sulfate, 1.1 kT). The degree of dissociation for the counterions bound to the micelle can be calculated from the dependency of the CMC on the concentration of the counterions. The values of the ester sulfonates are also in the same range as for other typical ionic surfactants (Na ester sulfonates, 0.61 Ca ester sulfonates, 0.70 Na dodecyl sulfate, 0.66). 

Increased removal of phenanthrene from soil columns spiked with the rhamnolipid mixture synthesized by Pseudomonas aeruginosa UG2 has been demonstrated, and shown to depend both on the increased desorption of the substrate and on partitioning into micelles (Noordman et al. 1998). However, the addition of the biosurfactant from the same strain of Pseudomonas aeruginosa UG2 or of sodium dodecyl sulfate had no effect on the rate of biodegradation of anthracene and phenanthrene from a chronically contaminated soil. 

We may contrast this behavior to that found for AOT. As shown in Figure 1, the chromatograms for AOT exhibit sharp fronts and somewhat diffuse tails, intermediate in shape between the symmetrical peaks typical of conventional solutes and the highly asymmetric chromatograms obtained for sodium dodecyl sulfate micelles in water (15). In addition, the concentration dependence of Mp" for AOT is gradual, not abrupt as for lecithin. These differences may be attributed to the lability of the AOT micelles which makes the observed retention time quite sensitive to the initial concentration (12) and leads to broadened chromatograms. 

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]. 

MEKC is a CE mode based on the partitioning of compounds between an aqueous and a micellar phase. This analytical technique combines CE as well as LC features and enables the separation of neutral compounds. The buffer solution consists of an aqueous solution containing micelles as a pseudo-stationary phase. The composition and nature of the pseudo-stationary phase can be adjusted but sodium dodecyl sulfate (SDS) remains the most widely used surfactant. 

A., Testa, B. The relative partitioning of neutral and ionised compounds in sodium dodecyl sulfate micelles measured by micellar electrokinetic capillary chromatography. Eur. J. Pharm. Sci. 2002, 75, 225-234. 

Recently, the newly developed time-resolved quasielastic laser scattering (QELS) has been applied to follow the changes in the surface tension of the nonpolarized water nitrobenzene interface upon the injection of cetyltrimethylammonium bromide [34] and sodium dodecyl sulfate [35] around or beyond their critical micelle concentrations. As a matter of fact, the method is based on the determination of the frequency of the thermally excited capillary waves at liquid-liquid interfaces. Since the capillary wave frequency is a function of the surface tension, and the change in the surface tension reflects the ion surface concentration, the QELS method allows us to observe the dynamic changes of the ITIES, such as the formation of monolayers of various surfactants [34]. 

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