Sodium dodecyl sulphate /water system

Figure 3. Phase diagrams of the system water sodium dodecyl sulphate/alkanols benzene (a) ethanol (b) 2-propanol (c) 1-propanol(d) 1-butanol (e) 1-pentanol (f) 1-hexanol (g) 1-heptanol.

Shergold. H.L. and Mellgren, O., Concentration of minerals at the oil-water interface Hematite-iso-octane-water system in the presence of sodium dodecyl sulphate, Trans. IMMC, 78, 121, 1969. 

The condensation method begins with molecular units, and the particles are built-up by a process of nucleation typical example is the preparation of polymer lattices, in which case the monomer (e.g., styrene or methylmethacrylate) is emulsified in water using an anionic or nonionic surfactant (e.g., sodium dodecyl sulphate or alcohol ethoxylate). A polymeric surfactant is also added to ensure the long-term colloid stabiHty of the resulting latex. An initiator such as potassium persulphate is then added and, when the temperature of the system has increased, initiation occurs that results in formation of the latex [polystyrene or poly(methylmethacrylate)]. 

Lyotropic liquid crystals are made up of two or more components. Generally, one of the components is an amphiphile (containing a polar head group attached to one or more long hydrocarbon chains) and another is water. A familiar example of such a system is soap (sodium dodecyl sulphate) in water. As the water content is increased several mesophases are obtained. The types of molecular packing in these mesophases are represented schematically in figs. 1.2.1 and 1.2.2, but several modifications of these structures exist. ... 

Figure 20.14. The viscosity (filled circles) of a solution of a hydrophobically modified water-soluble polymer and a surfactant increases as the concentration of micelles increases. The system illustrated is that of hydroxyethyl cellulose (1 wt%) and sodium dodecyl sulphate, upon the addition of an electrolyte (NaCl). (S. Nilsson, Ph. D. Thesis, Lund University, Sweden, 1999)...

From the experimental results obtained three liquid-liquid systems have been selected to be included here aniline/water, ethylacetate/water and ethylacetoacetate/water. The selected surfactants are SDS (sodium dodecyl sulphate), which is anionic, DTAB (dodecyl tri-methyl ammonium bromide), which is cationic, and Atlas G1300 (polyoxyethylene triglyceride ester) which is non-ionic. 

Abstract The scope of this work consisted of precipitating directly zinc oxide particles from zinc nitrate and zinc sulphate solutions using sodium hydroxide at pH 10,5, 2 h and 25 or 60 °C. For the zinc nitrate system, the effect of additives at 25 °C, such as sodium sulphate and sodium dodecyl sulphate, was also investigated. Precipitated powders were characterized in terms of their crystalline structure (X-ray diffraction), morphology and size (scanning electron microscopy, transmission electron microscopy). Precipitation in distilled water with zinc nitrate produced homogeneous star-type particles (1 /rm) composed of assembled 30-nm crystallites at 25 °C and ellipsoidal and spherical particles (100 nm to 1 fim) at 60 °C. On the other hand, for the zinc sulphate system at 25 °C, several different morphologies were obtained as ellipsoids (250 x 800 nm),... 

The kinetics of the reaction between Ni (aq) and the bidentate ligand pyridine-2-azo-phenol has been studied in different colloidal systems, namely, the aqueous micellar system formed by sodium dodecyl sulphate and an inverse-micellar system based on aerosol-OT, water and heptane. The reaction occurs at the surfactant-water interface in both colloidal systems and a kinetic treatment appropriate to a surface reaction is derived. The rates, mechanism and energetics are found to be similar for the reaction in both media. Activation energies are close to that measured in bulk water indicating that the rate-determining step in the reaction is loss of a water molecule from the nickel ion in all the media investigated. 

The anionic surfactant sodium dodecyl sulphate was used to form the aqueous micellar system. In order to ensure that no protonated or de-protonated species were participating in the reaction the pH behaviour of the system was studied spectro-photometrically in both water and micellar solutions. The approximate derived pK values in both bulk water and micellar SDS are shown below. 

Ekwall and Baltcheffsky [265] have discussed the formation of cholesterol mesomorphous phases in the presence of protein-surfactant complexes. In some cases when cholesterol is added to these solutions a mesomorphous phase forms, e.g. in serum albumin-sodium dodecyl sulphate systems, but this does not occur in serum albumin-sodium taurocholate solutions [266]. Cholesterol solubility in bile salt solutions is increased by the addition of lecithin [236]. The bile salt micelle is said to be swollen by the lecithin until the micellar structure breaks down and lamellar aggregates form in solution the solution is anisotropic. Bile salt-cholesterol-lecithin systems have been studied in detail by Small and coworkers [267-269]. The system sodium cholate-lecithin-water studied by these workers gives three paracrystalline phases I, II, and III shown in Fig. 4.37. Phase I is equivalent to a neat-soap phase, phase II is isotropic and is probably made up of dodecahedrally shaped lecithin micelles and bile salts. Phase III is of middle soap form. The isotropic micellar solution is represented by phase IV. The addition of cholesterol in increasing quantities reduces the extent of the isotropic... 

The surfactant sodium dodecyl sulphonate (Ci2H2sS03Na) and its sulphate adsorb electrostatically on hematite at low solute concentrations (Han et al., 1973). Hydro-phobic effects operate at high concentrations due to the incompatibility of the hydrocarbon part of the molecule with water. This involves condensation of the alkyl chains at the surface (hemi-micelle interactions), which lowers the free energy of the system and reverses the surface charge. 

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