Sodium dodecyl sulfate-water system

Fig. 6.6 Phase diagram of the sodium dodecyl sulfate-water system near the Krafft point Tk. (From Ref. 86. Reproduced by permission of Pergamon Press.)...

FIGURE 15.2. Prediction of partition coefficients for sodium dodecyl sulfate micellar systems using separate MLR for each database (a) and a single MLR for all databases (b). Databases (O) data compiled by Sprunger et al. (74) and ( ) by Quina et al. (75) for distribution between water and SDS ( ) data compiled by Kelly et al. (25) and ( ) by Poole and Poole (30) using MEKC. 

The phase diagram of sodium dodecyl sulfate-water is representative of many ionic systems (Figure 3.7) [5], In Figure 3.7 Liquid is the aqueous micellar phase Ha is the hexagonal lyotropic liquid crystal, sometimes called the middle phase and La is the lamellar lyotropic liquid crystal, sometimes called the neat phase. On the surfactant-rich side, several hydrated solid phases are present. 

While the Lewis acid-catalyzed aldol reactions in aqueous solvents described above are catalyzed smoothly by several metal salts, a certain amount of an organic solvent such as THF had still to be combined with water to promote the reactions efficiently. This requirement is probably because most substrates are not soluble in water. To avoid the use of the organic solvents, we have developed a new reaction system in which metal triflates catalyze aldol reactions in water with the aid of a small amount of a surfactant, such as sodium dodecyl sulfate (SDS). 

In this paper we apply basic solution thermodynamics to both the adsorption of single surfactants and the competitive adsorption of two surfactants on a latex surface. The surfactant system chosen in this model study is sodium dodecyl sulfate (SDS) and nonylphenol deca (oxyethylene glycol) monoether (NP-EO o) These two surfactants have very different erne s, i.e. the balance between their hydrophobic and hydrophilic properties are very different while both are still highly soluble in water. 

Where this factor plays a role, the hydrophobic interaction between the hydrocarbon chains of the surfactant and the non-polar parts of protein functional groups are predominant. An example of this effect is the marked endothermic character of the interactions between the anionic CITREM and sodium caseinate at pH = 7.2 (Semenova et al., 2006), and also between sodium dodecyl sulfate (SDS) and soy protein at pH values of 7.0 and 8.2 (Nakai et al., 1980). It is important here to note that, when the character of the protein-surfactant interactions is endothermic (/.< ., involving a positive contribution from the enthalpy to the change in the overall free energy of the system), the main thermodynamic driving force is considered to be an increase in the entropy of the system due to release into bulk solution of a great number of water molecules. This entropy... 

TLC separation of DNP-amino acids may be carried out on cellulose [14] or on polyamide layers [15,16] with several types of solvent systems. A two-dimensional separation of DNP-amino acids on cellulose with toluene—2-chloroethanol—pyridine—5 N ammonia (5 3 1.5 6.5) and saturated ammonium sulfate-water-sodium dodecyl sulfate (25 ml 175 ml 0.144 g) is shown in Fig.4.8. A similar separation on polyamide layers is... 

The ultralow interfacial tension can be produced by using a combination of two surfactants, one predominantly water soluble (such as sodium dodecyl sulfate) and the other predominantly oil soluble (such as a medium-chain alcohol, e.g., pentanol or hexanol). In some cases, one surfactant may be sufficient to produce the microemulsion, e.g., Aerosol OT (dioctyl sulfosuccinate), which can produce a W/O microemulsions. Nonionic surfactants, such as alcohol ethoxylates, can also produce O/W microemulsions, within a narrow temperature range. As the temperature of the system increases, the interfacial tension decreases, reaching a very low value near the phase inversion temperature. At such temperatures, an O/W microemulsion may be produced. 

A predictive molecular thermodynamics approach is developed for microemulsions, to determine their structural and compositional characteristics [3.7]. The theory is built upon a molecular level model for the free energy change. For illustrative purposes, numerical calculations are performed for the system water, cyclohexane, sodium dodecyl sulfate as surfactant, pentanol as cosurfactant and NaCl as electrolyte. The droplet radius, the thickness of the surfactant layer at the interface, the number of molecules of various species in the droplets, and the distribution of the components between droplets and the continuous phase are calculated. The theory also predicts the transition from a mi-... 

Calculations were carried out for a system consisting of the anionic surfactant sodium dodecyl sulfate, 1-pen-tanol (cosurfactant), cyclohexane, and water containing 0.3 M NaCl. As mentioned atthe very beginning, thechoice of this system was dictated by the possibility of identifying various types of phase behaviors for the same chemical components by merely changing the amount of added alcohol. In all calculations, we assumed the coexistence of an excess dispersed phase. This means that the droplet microemulsion phase is part of a two-phase system and that the amount of dispersed phase present in the droplet is the maximum achievable. 

The calculated results in the absence of electrolyte will be now compared with the experimental results obtained regarding a lamellar lyotropic liquid crystal SDS (sodium dodecyl sulfate)/pentanol/water/dodecane swollen in a mixture of dodecane and pentanol.24 The weight fraction water/surfactant was 1.552 from the dilution line in the phase diagram, we calculated that the initial concentration of pentanol in the oil-free system was 29 wt % and the concentration of pentanol in the dodecane-based diluant was 8 wt %. The experimental values for the repeat distance were obtained from the X-ray diffraction spectrum (Figure 2 in ref 24) for various dodecane concentrations. 

Indium metal in water reduces a-halocarbonyl compounds and benzyl iodides to the corresponding dehalogenated products in excellent yields under sonication, though simple alkyl and aryl iodides remain inert under these conditions (Equation (97)).379 Similar dehalogenation in micellar systems in the presence of a catalytic amount of sodium dodecyl sulfate in water affords the corresponding parent carbonyl compounds in excellent yields (Equation (98)).380 The allylic iodide or acetate is reduced by indium into the corresponding 3-methylcephems and 3-methylenecephams in an aqueous system. The latter are converted into the former quantitatively under basic conditions (Scheme 110).381... 

Fang, J., and Venable, R. L. (1987), Conductivity study of the microemulsions system sodium dodecyl sulfate-hexylamine-heptane-water, /. Colloid Interface Sci, 116, 269-277. 

Later, Yoshikawa and Matsubara [40] further studied a non-linear system and proposed a mechanism for the periodic behaviour that involved the formation of inverted micelles that suddenly moved to the oil phase after the concentration of adsorbed surfactants reached a critical value. They extended the experiment to a water/oil/water three-phase system in a U-shaped glass tube that gave spontaneous and stable oscillatory behaviour over a long period [41]. Since then, various characteristics of non-linear behaviour have been investigated and several mechaiusms for the non-linear behaviour have been proposed by many research groups including ours[2,5,10,42-48] however, the mechanism at a molecular level has not been clarified yet and no consensus has been achieved. The difficulty in the explanation seems to come from not only the complexity and diversity of the systems, but also limitations of the observation methods that enable us to monitor dynamic molecular behaviour at liquid/liquid interfaces with sufficient interfacial selectivity and time resolution. In this section, the TR-QELS method has been applied to the investigation of W/NB—sodium dodecyl sulfate (SDS) two-phase system [10]. 

Figure lA. The solubility region for the pentanol solution in the system Water, sodium dodecyl sulfate (SDS) and pentanol. 

---