Micelles applications

N. Pena, G. Ruiz, A.J. Reviejo and J.M. Pingarron, Graphite-teflon composite bienzyme electrodes for the determination of cholesterol in reversed micelles. Application to food samples, Anal. Chem., 73(6) (2001) 1190-1195. 

Motomura et al. proposed a method of evaluation of various thermodynamic properties of micellar solutions from the surface tension data in the framework of the pseudophase treatment of micellisation [50, 52-55]. According to these authors, the micellar composition at the CMC can be found from the functional dependence of the CMC on the overall surfactant mole fraction using an analogy to the method proposed by Nguyen et al. [49], The approach of Motomura et al. [50] gives also a possibility to determine the relation between the composition of the surface layer and the micelles. Application of the Gibbs-Duhem equation to the whole... 

Surface active electrolytes produce charged micelles whose effective charge can be measured by electrophoretic mobility [117,156]. The net charge is lower than the degree of aggregation, however, since some of the counterions remain associated with the micelle, presumably as part of a Stem layer (see Section V-3) [157]. Combination of self-diffusion with electrophoretic mobility measurements indicates that a typical micelle of a univalent surfactant contains about 1(X) monomer units and carries a net charge of 50-70. Additional colloidal characterization techniques are applicable to micelles such as ultrafiltration [158]. 

Other solubilization and partitioning phenomena are important, both within the context of microemulsions and in the absence of added immiscible solvent. In regular micellar solutions, micelles promote the solubility of many compounds otherwise insoluble in water. The amount of chemical component solubilized in a micellar solution will, typically, be much smaller than can be accommodated in microemulsion fonnation, such as when only a few molecules per micelle are solubilized. Such limited solubilization is nevertheless quite useful. The incoriDoration of minor quantities of pyrene and related optical probes into micelles are a key to the use of fluorescence depolarization in quantifying micellar aggregation numbers and micellar microviscosities [48]. Micellar solubilization makes it possible to measure acid-base or electrochemical properties of compounds otherwise insoluble in aqueous solution. Micellar solubilization facilitates micellar catalysis (see section C2.3.10) and emulsion polymerization (see section C2.3.12). On the other hand, there are untoward effects of micellar solubilization in practical applications of surfactants. Wlren one has a multiphase... 

It is of particular interest to be able to correlate solubility and partitioning with the molecular stmcture of the surfactant and solute. Likes dissolve like is a well-wom plirase that appears applicable, as we see in microemulsion fonnation where reverse micelles solubilize water and nonnal micelles solubilize hydrocarbons. Surfactant interactions, geometrical factors and solute loading produce limitations, however. There appear to be no universal models for solubilization that are readily available and that rest on molecular stmcture. Correlations of homologous solutes in various micellar solutions have been reviewed by Nagarajan [52]. Some examples of solubilization, such as for polycyclic aromatics in dodecyl sulphonate micelles, are driven by hydrophobic... 

The production of organic polymeric particles in tire size range of 30-300 nm by emulsion polymerization has become an important teclmological application of surfactants and micelles. Emulsion polymerization is very well and extensively reviewed in many monographs and texts [67, 68], but we want to briefly illustrated tire role of micelles in tliis important process. 

Dunn A S 1989 Polymerization in micelles and microemulsions Comprehensive Polymer Science—the Synthesis, Characterization, Reactions and Applications of Polymers vo 4, ed G C Eastmond, A Ledwith, S Russo and P Sigwalt (New York Pergamon) pp 219-24... 

Although the remainder of this contribution will discuss suspensions only, much of the theory and experimental approaches are applicable to emulsions as well (see [2] for a review). Some other colloidal systems are treated elsewhere in this volume. Polymer solutions are an important class—see section C2.1. For surfactant micelles, see section C2.3. The special properties of certain particles at the lower end of the colloidal size range are discussed in section C2.17. 

The use of dienophile 5.1 also allows study of the effect of micelles on the Lewis-acid catalysed reaction. These studies are described in Section 5.2.2. and represent the first in-depth study of Lewis-acid catalysis in conjunction with micellar catalysis , a combination that has very recently also found application in synthetic organic chemistry . ... 

A number of examples have been studied in recent years, including liquid sulfur [1-3,8] and selenium [4], poly(o -methylstyrene) [5-7], polymer-like micelles [9,11], and protein filaments [12]. Besides their importance for applications, EP pose a number of basic questions concerning phase transformations, conformational and relaxational properties, dynamics, etc. which distinguish them from conventional dead polymers in which the reaction of polymerization has been terminated. EP motivate intensive research activity in this field at present. 

Another example of OTHdC application is the study of the association/ dissociation of copolymer micelles. Using the light-scattering technique, the... 

For the separation of amino acids, the applicability of this principle has been explored. For the separation of racemic phenylalanine, an amphiphilic amino acid derivative, 1-5-cholesteryl glutamate (14) has been used as a chiral co-surfactant in micelles of the nonionic surfactant Serdox NNP 10. Copper(II) ions are added for the formation of ternary complexes between phenylalanine and the amino acid cosurfactant. The basis for the separation is the difference in stability between the ternary complexes formed with d- or 1-phenylalanine, respectively. The basic principle of this process is shown in Fig. 5-17 [72]. 

Monomers of die type Aa B. are used in step-growth polymerization to produce a variety of polymer architectures, including stars, dendrimers, and hyperbranched polymers.26 28 The unique architecture imparts properties distinctly different from linear polymers of similar compositions. These materials are finding applications in areas such as resin modification, micelles and encapsulation, liquid crystals, pharmaceuticals, catalysis, electroluminescent devices, and analytical chemistry. 

From experience in metalworking applications it is known that ether carboxylates may improve the existing corrosion protection of formulations [66]. From pKj studies described by Aalbers [49], an internal neutralization of the ether carboxylate micelles can be concluded resulting in less anionic character than, for example, alkyl sulfates therefore also combination with quats are possible without any problem. 

Because of their preferential use as detergents, the main interest in the physicochemical properties of the salts of a-sulfo fatty acid esters is related to their behavior in aqueous solution and at interfaces. In principle these are surface-active properties of general interest like micelle formation, solubility, and adsorption, and those of interest for special applications like detergency, foaming, and stability in hard water. 

ELP-based triblock copolypeptides have also been used to produce stimulus-responsive micelles, and Chaikof and coworkers envisioned the possible application of these micelles as controlled drug delivery vehicles. These amphiphilic triblock copolymers were constructed from two identical hydrophobic ELP endblocks and a hydrophilic ELP midblock. Below the transition temperature, loose and monodispersed micelles were formed that reversibly contracted upon heating, leading to more compact micelles with a reduced size [90]. 

Studies of reversed micelles dispersed in supercritical fluids have shown their ability to solubihze hydrophihc substances, including biomolecules and dyes, opening the door to many new applications [60,61]. In particular, solutions of reversed micelles in liquid and supercritical carbon dioxide have been suggested as novel media for processes generating a minimum amount of waste and with a low energy requirement [62]. 

Other applications are based on the use of solutions of reversed micelles as templates. For example, solutions of reversed micelles have been employed as a matrix to control the porosity of cross-linked polymer resins. The pore size of the polymers was controlled by varying the amounts of water in the AOT-reversed micelles [67]. 

It has been observed that whereas the catalytic activity of malic dehydrogenase in water is not influenced by pressure, in reversed micelles it shows a bell-shaped dependence, suggesting regulation of the enzymatic activity by pressure application, which cannot be realized in aqueous solutions [180],... 

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