Water-soluble ionic surfactant

The catalysts can be obtained by a coprecipitation method consisting of two steps (Figure 6.2). In the first step, a stable suspension of protected metal nanoparticles is obtained according to the method reported by Schulz and co-workers [75-77]. The metal particles are prepared in the presence of a highly water-soluble ionic surfactant which is able, due to its nature, to modulate the particle size and to prevent their aggregation. Modifying parameters such as pH, temperature and surfactant concentration, it is possible to tune the metal particle size [71]. Moreover, the role of the... 

Water-miscible surfactant molecules contain both a hydrophobic and hydrophilic portion, and can solubilize many poorly water-soluble drugs. Surfactants can also self-assemble to form micelles once the surfactant monomer concentration reaches the critical micelle concentration. Thus surfactants can solubilize drug molecules by either a direct cosolvent elfect or by uptake into micelles. The non-ionic surfactants in commercially available solubilized oral formulations include polyoxyl 35 castor oil (cremophor EL), polyoxyl 40 hydrogenated... 

In media of low dielectric constant, electrostatic stabilization is of little importance. Colloidal dispersions in non-aqueous media are thus more likely to be stabilized by steric barriers formed by adsorbed surfactants and polymers. Relatively little work has been done on the adsorption of surfactants on to solids from non-aqueous solvents, a limiting factor of course being the insolubility of many surfactants in solvents other than water. Non-ionic surfactants tend to be soluble in both aqueous and non-polar solvent systems. Rupprecht [6] has made a series of investigations of adsorption of non-ionic alkyl polyethers on to silica in various organic solvents. Fig. 9.20 shows some of the adsorption isotherms for nonylphenol Eg. 5 from dichloromethane, n-butanol, n-propanol, ethanol, 1,4-dioxan and DMSO. As might be expected, adsorption is greatest from the dichloromethane and the effect of increasing polarity is clearly seen with the three alcohols. 

Two PEO-PPO-PEO three-block copolymers of the Synperonic series - F108 and P104 [28, 29] - have been employed. PPO represents the middle hydrophobic block B and both hydrophilic PEO form the two terminal chains A. These commercial, non-ionic, water-soluble polymeric surfactants were used as obtained from BASF. They are pure though not monodisperse. The molecular masses and average EO/PO contents are known from the manufacturer and yield approximate... 

Capillary Electrophoresis. Capillary electrophoresis (ce) is an analytical technique that can achieve rapid high resolution separation of water-soluble components present in small sample volumes. The separations are generally based on the principle of electrically driven ions in solution. Selectivity can be varied by the alteration of pH, ionic strength, electrolyte composition, or by incorporation of additives. Typical examples of additives include organic solvents, surfactants (qv), and complexation agents (see Chelating agents). 

The two-phase titration is based on the reaction of anionic surfactants with cations—normally large cationic surfactants—to form an ion pair. The preferred cationic is benzethonium chloride (Hyamine 1622, 1) because of the purity of the commercially available product. On neutralization of the ionic charges, the ion pair has nonpolar character and can be extracted continuously into the organic phase, e.g., chloroform, as it is formed. The reaction is monitored by addition of a water-soluble cationic dye, dimidium bromide (2), and a water-soluble anionic dye, disulfine blue (3). The cationic dye forms an extractable... 

The solubility of numerous ionic surfactants in water is strongly reduced in the presence of divalent cations. Stability in hard water is thus an important fact for surfactants used as detergents. Their stability can be measured as the amount of divalent cations at which the formation of a poorly soluble surfactant salt leads to permanent turbidity. The values given in the literature can only be... 

As alternatives to amphiphilic betaines, a wide range of cationic, anionic, and non-ionic surfactants including environmentally benign sugar soaps have been successfully used as colloidal stabilizers [201]. Electrochemical reduction of the metal salts provides a very clean access to water soluble nanometal colloids [192]. 

Another solution to the problem of catalyst/product separation is the biphasic catalysis. The liquid biphasic catalysis became an attractive technology for potential commercial application of enantioselective homogeneous catalysis. The most important features of such systems are related to the fact that both reaction rate and e.s. may be influenced by the number of ionic groups in water-soluble ligand or by addition of surfactants. Descriptions of water-soluble ligands and the recent results in the rapidly progressing area of biphasic enantioselective catalysis are available in recent reviews [255,256],... 

The surface active agents (surfactants) may be cationic, anionic or non-ionic. Surfactants commonly used are cetyltrimethyl ammonium bromide (CTABr), sodium lauryl sulphate (NaLS) and triton-X, etc. The surfactants help to lower the surface tension at the monomer-water interface and also facilitate emulsification of the monomer in water. Because of their low solubility surfactants get fully dissolved or molecularly dispersed only at low concentrations and at higher concentrations micelles are formed. The highest concentration where in all the molecules are in dispersed state is known as critical micelle concentration (CMC). The CMC values of some surfactants are listed in table below. 

High polarity is one of the reasons why both the ionic and amphoteric surfactants, and especially their metabolites, are difficult to detect. This property, however, is important for the application tasks of surface-active compounds, but is also the reason for their high water solubility. Due to this fact, their extraction and concentration from the water phase, which can be carried out in a number of very different ways, is not always straightforward. Furthermore, they are often not volatile without decomposition, which thus prevents application of gas chromatographic (GC) separation techniques combined with appropriate detection. This very effective separation method in environmental analysis is thus applicable only for short-chain surfactants and their metabolites following derivatisation of the various polar groups in order to improve their volatility. 

The non-ionic surfactants do not produce ions in aqueous solution. The solubility of non-ionic surfactants in water is due to the presence of functional groups in the molecules that have a strong affinity for water. Similarly to the anionic surfactants, and any other group of surfactants, they also show the same general property of these products, which is the reduction of the surface tension of water. 

Solubilisation can best be illustrated by considering the phase diagrams of non-ionic surfactants containing poly(oxyethylene oxide) head groups. Such surfactants do not generally need a cosurfactant for microemulsion formation. At low temperatures, the ethoxylated surfactant is soluble in water... 

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