Organized surfactant systems

A brief description of the structural features and relevant properties of different organized assemblies formed from surfactant molecules is presented. Next, the use and application of these organized surfactant systems in separation science is surveyed. Several possible new areas for future developments employing these ordered media are mentioned. 

TABLE VI. Comparison of some Binding Constants for the Interaction of Solutes with Selected Organized Surfactant Systems... 

Shinoda, K. and Lindman, B. (1987) Organized surfactant systems Microemulsions. Langmuir, 3, 135-149. 

R. Schoemacker and K. Hohnberg, Reactions in organized surfactant systems, in Microemulsions Background, New Concepts, Applications, Perspectives, ed. S. Stubenrauch, Blackwell Publishing, Oxforcl 2009, p. 148. 

The phosphinated ligands 135 and 136 prepared from poly(acrylic acid) and from poly(ethyleneimine), respectively, gave active hydroformylation catalysts in reaction with [Rh(acac)(CO)2]. Under the conditions of Table 4.6 low conversions were observed in aqueous/organic biphasic systems, due to the low solubility of 1-octene. Addition of a surfactant (SDS) or an organic co-solvent (MeOH) led to dramatic increases in the yield of aldehydes, revealing the high intrinsic activity of the catalyst [120]. 

A paper contributed by J. E. Desnoyers, R. Beaudoin, C. Roux, and C. Perron described the use of microemulsions as a possible tool for the extraction of oil from tar sands. Using a technique called flow microcalorimetry recently developed at the University of Sherbrooke, these researchers studied the structure and stability of organic microphases in aqueous media. These microphases can be stabilized by surfactants and can dissolve large quantities of oil. In a similar vein, D. F. Gerson, J. E. Zajic, and M. D. Ouchi (University of Western Ontario) described the extraction of bitumen from Athabasca tar sands by a combined solvent-aqueous-surfactant system. 

In the real world, soluble organic materials may be present in the aqueous surfactant system. As with micelles, it is important to know how these affect mixed admicelle formation and how well these organics are solubilized in the admicelle (adsolubi1ized). 

In MECC anionic surfactants are most frequently used, but cationic surfactants are also very popular. In addition, chiral surfactants, nonionic surfactants, zwitterionic surfactants, biological surfactants, or mixtures of each are finding increasing use. In all categories, variations in alkyl chain length will affect resolution or selectivity, as will changes in buffer concentration, pH, and temperature or the use of additives such as metal ions or organic modifiers. Typical surfactant systems used in MECC are shown in Table 5.3. 

In this paper we discuss results obtained in constructing the organized molecular systems for PET based on the use of ultrathin lipid or surfactant membranes, and in studying the mechanisms of PET in such systems. The state of the art in conjugation of PET across membranes with catalytic reactions of water reduction to dihydrogen and its oxidation to dioxygen will be also briefly discussed. 

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. 

Tzialla AA, Kalogeris E, Goumis D et al (2008) Enhanced catalytic performance and stability of chloroperoxidase from Caldariomyces fumago in surfactant free ternary water-organic solvent systems. J Mol Catal B Enzym 51 24—35... 

Figure 5. Simplified extraction mechanism for the alkylammonlum cationic surfactant system In organic solvents. CA refers to a solubilized co-extractant, X Is the counterion of the surfactant, and X and W refer to the species (anions or anionic metal complexes) to be extracted from the aqueous phase.

Based upon the use of nonionic surfactant systems and their cloud point phase separation behavior, several simple, practical, and efficient extraction methods have been proposed for the separation, concentration, and/or purification of a variety of substances including metal ions, proteins, and organic substances (429-441. 443.444). The use of nonionic micelles in this regard was first described and pioneered by Watanabe and co-workers who applied the approach to the separation and enrichment of metal ions (as metal chelates) (429-435). That is, metal ions in solution were converted to sparingly water soluble metal chelates which were then solubilized by addition of nonionic surfactant micelles subsequent to separation by the cloud point technique. Table XVII summarizes data available in the literature demonstrating the potential of the method for the separation of metal ions. As can be seen, factors of up to forty have been reported for the concentration effect of the separated metals. 

In our laboratories, extensive use has been made of vapor pressure (14-18) and membrane methods ( 2, 3, 19, 20) to Infer thermodynamic results for ternary aqueous systems containing an ionic or a nonionic surfactant and an organic solute. The most precise solubilization measurements ever reported have been obtained with an automated vapor pressure apparatus for volatile hydrocarbon solutes such as cyclohexane and benzene, dissolved In aqueous solutions of sodium octylsulfate and other Ionic surfactants (15, 16). A manual vapor pressure apparatus has been employed to obtain somewhat less precise results for solutes of lower volatility (17, 18). Recently, semi-equilibrium dialysis (19, 20) and MEUF (2) methods have been used to investigate solute-surfactant systems in which the organic solubilizates are too involatile to study by ordinary vapor pressure methods. 

Sarda S, Heughebaert M, Lebugle A (1999) Influence of the type of surfactant on the formation of calcium phosphate in organized molecular systems. Chem Mater 11(10) 2722-2727... 

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