Sodium lauryl sulfate micelles

However, one can change the structure in a known fashion, micelle to rod, etc., with remarkable precision [Thomas, J. K. Chem. Rev. 1980, 80, 283]. In actual fact, a sodium lauryl sulfate micelle is a very precise entity containing 71 1 units. A precise cooperative effect forms the micelle. If you change the conditions of the solution, such as the salt concentration, etc., then you can make other structures which are well identified. 

If a photoactive probe molecule is buried in the core of an anionic micelle, biphotonic excitation generates an upper excited state from which electron ejection to solvent can occur. With pyrene (Py) imbedded within a sodium lauryl sulfate micelle (NaLS), for example, electron ejection to form a hydrated electron occurs, Eq. 6 [27],... 

A) Graphs of surface tension as well as osmotic pressure plotted versus concentration of sodium lauryl sulfate, demonstrating critical micelle concentration at about 0.21 percent. B) Representation of a sodium lauryl sulfate micelle. 

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... 

Howard [27] determined dissolved aluminium in seawater by the micelle-enhanced fluorescence of its lumogallion complex. Several surfactants (to enhance fluorescence and minimise interferences), used for the determination of aluminium at very low concentrations (below 0.5 pg/1) in seawaters, were compared. The surfactants tested in preliminary studies were anionic (sodium lauryl sulfate), non-ionic (Triton X-100, Nonidet P42, NOPCO, and Tergital XD), and cationic (cetyltrimethylammonium bromide). Based on the degree of fluorescence enhancement and ease of use, Triton X-100 was selected for further study. Sample solutions (25 ml) in polyethylene bottles were mixed with acetate buffer (pH 4.7, 2 ml) lumogallion solution (0.02%, 0.3 ml) and 1,10-phenanthroline (1.0 ml to mask interferences from iron). Samples were heated to 80 °C for 1.5 h, cooled, and shaken with neat surfactant (0.15 ml) before fluorescence measurements were made. This procedure had a detection limit at the 0.02 pg/1 level. The method was independent of salinity and could therefore be used for both freshwater and seawater samples. 

DR. THOMAS The kinetic parameters of micelles are very well known, having been determined by temperature-jump relaxation methods and various other techniques. There are several kinetic events which can be described. First of all, the fastest event is the exchange of the counter ion (e.g., the sodium counter ion, in sodium lauryl sulfate). These ions exchange... 

Surfactants can act like lipids or emulsifiers in solubilizing flavor materials in surfactant micelles. Headspace analysis techniques were used to follow the release of several common dentifrice flavorants from a solution containing the surfactant sodium lauryl sulfate. Water/micelle partition coefficients were derived to describe the solubilization of the flavorants in tiie surfactant micelle (76). Initially, the flavor is solubilized in the surfactant micelle. As both the micelle and flavor concentration decrease on dilution, flavor compounds, which are highly soluble in the micelle, preferentially increase in the headspace [HGURE11]. 

The ionic field of micells increases the efficiency of photoinduced charge separation. Laser flash photolysis showed a longer lifetime of the e formed by irradiation of a donor molecule (D pyrene, perylene etc.) solubilized in anionic micells such as sodium lauryl sulfate (SDS) than in a non-micell systems 19b). This is why the e is repulsed by the anionic field at the micellar surface into the bulk solution (Eq. (10)). 

Penetration enhancers have different mechanisms of action depending on their physicochemical properties. Some examples of penetration enhancers and their mechanisms are bile salts (micellization and solubilization of epithelial lipids), fatty acids such as oleic acid (perturbation of intracellular lipids) [25,26], azone (l-dodecylazacycloheptan-2-one) (increasing fluidity of intercellular lipids), and surfactants such as sodium lauryl sulfate (expansion of intracellular spaces). The complete list of enhancers and their mechanism of actions are discussed in detail in Chapter 10. 

Micellar effects were found to be variable and dependent on the type of micelle employed. Cationic micelles, such as cetyltrimethylammonium bromide, inhibited hydration. Anionic micelles formed from sodium lauryl sulfate (NaLS) produced a small amount of catalysis at low concentration, exp actually passing through a maximum at [NaLS] < the critical micelle concentration (cmc). On the other hand, micelles formed from monopotassium -dodecyl phosphate in unbuffered water give impressive catalysis relative to water itself. Detailed discussion of these effects is given in Reference 80. 

For turbidity measurements, a stock solution of desired mole ratio of sodium lauryl sulfate to BC-840 was prepared on a weight basis. The stock solution was diluted volumetrically to a series of different concentrations. These diluted solutions were allowed to stand overnight for equilibration of micelles. Solutions were filtered four times under pressure through HAWP 0.25 filter directly into scattering cells for measurements. 

KOH affects the size of the changed micelles (12.16-18). For mixed surfactant systems, this effect may be different for different values of surfactant ratios of the mixed surfactants. Furthermore, it was observed, during the earlier period of the present study, that the dilute solutions of sodium lauryl sulfate beccime turbid in the presence of KOH, presumably due to alkaline hydrolysis. Therefore, KOH was not used in this study. 

Materials and Polymerization. Styrene and methyl methacrylate were obtained from commercial sources and were distilled to remove inhibitor. After distillation, the monomers were stored, under nitrogen, in a refrigerator. For the mixed emulsifier system, Emulphogene BC840(GAF), tridecyloxy-polyethylene-oxyethanol, was used as the nonionic constituent, and sodium lauryl sulfate (K and K Labs) was used as the ionic constituent. The sodium lauryl sulfate was at a concentration below its cms whereas the BD-840 was at a concentration above its cmc. This emulsifier system has been shown to yield mixed micelles (2)/ having a low ionic change (2)/ which produce latlces with rather narrow particle size distributions (2 ) ... 

Most of the work concerned with micellar catalysis of nucleophilic substitution refers to reactions of the Aac2 and SN2 types and will not be reviewed here. To date only a few systems have been examined in which a micellar medium affects the partitioning of solvolytic reactions between unimolecular and bimolecular mechanisms. The effects of cationic (hexadecyltrimethylammonium bromide = CTAB) and anionic (sodium lauryl sulfate = NaLS) micelles on competitive SN1 and SN2 reactions of a-phenylallyl butanoate 193) have been investigated189. The rate of formation of the phenylallyl cation 194) is retarded by both surfactants probably as a consequence of the decreased polarity of the micellar pseudo phase. The bimolec-... 

After cyclodextrins and co-solvents, other approaches can be applied including the use of surfactants and micelle forming agents. Surfactants can be classified as amphoteric (lecithin), non-ionic (Tween 80 or Cremophor EF) or ionic (sodium lauryl sulfate or sodium palmitate). Cremophor is a polyoxyethylenated castor oil derivative which is a common solubilizing excipient in a number of formulations including those for paclitaxel, propofol, teniposide and clanfenur... 

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