Surfactants in organic

Dispersants and detergents are surfactants in organic media and contain an oleophilic hydrocarbon part and a hydrophilic polar part. 

Usually, activities of enzymes (hydrogenases included) are investigated in solutions with water as the solvent. However, enhancement of enzyme activity is sometimes described for non-aqueous or water-limiting surroundings, particular for hydrophobic (or oily) substrates. Ternary phase systems such as water-in-oil microemulsions are useful tools for investigations in this field. Microemulsions are prepared by dispersion of small amounts of water and surfactant in organic solvents. In these systems, small droplets of water (l-50nm in diameter) are surrounded by a monolayer of surfactant molecules (Fig. 9.15). The water pool inside the so-called reverse micelle represents a combination of properties of aqueous and non-aqueous environments. Enzymes entrapped inside reverse micelles depend in their catalytic activity on the size of the micelle, i.e. the water content of the system (at constant surfactant concentrations). 

Martinek, K., Levashov, A. V, Klyachko, N. L., Pantin, V. L, and Berezin, I. V. (1981). The principles of enzyme stabilization. 6. Catalysis by water-soluble enzymes entrapped into reversed micelles of surfactants in organic solvents. Biochem. 

An emulsifier system must cause the concentrate to disperse spontaneously into small, stable droplets when mixed with water. To accomplish this, the surfactant system must have a most favorable solubility relationship a proper balance between oil and water solubility or, in other words, a favorable hydrophile-lipophile balance in solubility. This balance in solubility is frequently referred to as HLB and was first described by Griffin (6). However, the HLB system is based on the structure of a surfactant molecule and, therefore, predicts the behavior of a single molecule. It does not take into account tr 3 fact that many surfactants form micelles in organic solutions. If a micelle is formed, its HLB may have no relationship to the HLB of the monomer unit. Therefore, to select an emulsifier well, we will need a better understanding of the behavior of surfactants in organic solvents. 

Extractions Utilizing Surfactants in Organic Solvents. The use of organic solvents containing surfactants in extractive metallurgy has probably been the most prevalent application of surfactants in chemical separations (1.5.240-262). Table XIII summarizes some of the... 

FIGURE 7.20 Settling rate variation of alumina suspensions upon adsorption of different surfactants in organic media. 

Rorig, H. and R. Stephan, Cationic surfactants in organic acid-based hard surface cleaners, Commun. Sorn. Com. Esp. Deterg., 21, 191,1990. 

Protein (enzyme) incorporation into reverse micelles of surfactant in organic solvents may be achieved by one of the following methods. 

Wang D, Hao J. Self-assembly fibrillar network gels of simple surfactants in organic solvents. Langmuir. 27(5) (2011) 1713-1717. 

Mansourpanah, Y., Madaeni, S. S., and Rahimpour, A. 2009. Fabrication and development of interfacial polymerized thin-fihn composite nanofiltration membrane using different surfactants in organic phase study of morphology and performance. Journal of Membrane Science 343 219-228. 

Kabanov, A.V., Levashov, A.V., Klyachko, N.L., Namyotkin, S.N., Pshezhetsky, A.V. 1988. Enzymes entrapped in reversed micelles of surfactants in organic solvents A theoretical treatment of the catalytic activity regulation. J. Theor. Biol. 133,... 

Another term, the critical solution temperature (CST), was introduced to designate the temperature beyond which the solubility of nonionic surfactants in organic solvents increases markedly, as marked by an inflection in the solubility curve. Mazer and Benedek used the critical micellar temperature (CMT) to refer to the phase boundary between a hydrated solid phase and a micellar phase." The CMT value was taken as the midpoint of the temperature range over which the hydrated solid phase clarified on slow warming with vigorous shaking. 

TABLE 4.21. Critical Micelle Concentrations for Some Surfactants in Organic Media... 

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