Micelles and microemulsion

2) the w/o in equilibrium with water (such as reverse micelles), and 

These systems are ako called Winsor (W) microemukion types I, II, and III, respectively. Formation of each of these systems depends on the conditions and composition of the phases and each type can be formed from another type by varying one or more of the parameter(s) of the system (salt, coemukifier, emulsifier structure 

1) a large increase in the interface (e.g., a droplet of radius 120 nm will disperse ca. 1800 microdroplets of radius 10 nm - a 12-fold increase in the interfacial area), and 

2) the formation of a mixed emulsifier/coemulsifier film (complex) at the oil/water interface, which is responsible for a very low surface tension (yi). 

Microemulsions (monomer swollen micellar solution, micellar emulsions, or spontaneous transparent emulsion) are dispersions of oil and water made with emulsifier and coemulsifier molecules. In many respects, they are small - scale versions of emulsions. They are homogeneous on a macroscopic scale but heterogeneous on a molecular scale. They consist of oil and water domains which are separated by emulsifier monolayers. 

---

Chevalier Y and Zemb T 1990 The structure of micelles and microemulsions Rep. Prog. Phys. 53 279-371... 

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... 

Zulauf M and Eicke FI 1979 Inverted micelles and microemulsions in the ternary system Fl20/aerosol-OT-isoctane as studied by photon correlation spectroscopy J. Phys. Chem. 83 480... 

Liquid Crystal Third Phase. In addition to micelles and microemulsion droplets, surfactants may form Hquid crystals. A Hquid crystal is a separate phase, which comes out of solution, not like the micelles or microemulsion droplets, which are microscopic entities within the solution. 

Other examples of organized molecular assemblies of interest for photocatalysis are (1) PC-A, PC-D or D-PC-A molecules where PC, A and D fragments are separated by rigid bridges (2) host-guest complexes (3) micelles and microemulsions (4) surfactant monolayers or bilayers attached to solid surfaces, and (5) polyelectrolytes [19]. 

Ornskov, E.,. Gottfries, M. Erickson, S. Folestad. Experimental modelling of drug membrane permeability by capillary electrophoresis using liposomes, micelles and microemulsions./. Pharm. Pharmacol. 2005, 57, 435 2. 

Zulauf, M and Eicke, H.F. "Inverted Micelles and Microemulsions in the Ternary System H20/Aerosol OT/Isooctane as Studied by Photon Correlation Spectroscopy," J. Phvs. Chem.. 1979, 82(4), 480 486. 

Hydrophobic solubilizates such as styrene (S) decrease the saponification rate of the EUP. Accordingly, the EUP-molecules in micelles containing S are more resistant against hydrolytic degradation than molecularly dissolved EUP-mole-cules. Obviously, the access of the base to the hydrophobic interior of these micelles and microemulsion droplets is more difficult. 

As the EUP is an emulsifier, an increase of the EUP/comonomer ratio not only causes an increase of the number of micelles and microemulsion droplets respectively but also of the number of microgels and, correspondingly, a decrease of their molar mass [110,126] and their diameter [127]... 

Because the presence of an electrolyte increases the dimensions of micelles and microemulsion droplets [115], it may be expected that in presence of ions the size of microgels is also increased. This expectation could be confirmed external electrolyte increases Mw (Fig. 21) as well as dz and [r ] (Fig. 22) up to the limit of the emulsion stability. Therefore, the addition of an external electrolyte to the reaction mixture for the ECP of EUP and comonomers is a means to vary the molar mass, the diameter and the intrinsic viscosity of microgels from EUP and comonomers deliberately. 

A microemulsion droplet is a multicomponent system containing oil, surfactant, cosurfactant, and probably water therefore there may be considerable variation in size and shape depending upon the overall composition. The packing constraints which dictate size and shape of normal micelles (Section 1) should be relaxed in microemulsions because of the presence of cosurfactant and oil. However, it is possible to draw analogies between the behavior of micelles and microemulsion droplets, at least in the more aqueous media. 

CTABr + C4H9OH, C5H,, OH or C6H13OH, + octane. Second-order rate constants in aq. micelles and microemulsion droplets compared... 

Endojexo ratios compared in water, micelles and microemulsions... 

Other aqueous aggregates (trialkylammonium aggregates, bile salt micelles and microemulsions) 439... 

OTHER AQUEOUS AGGREGATES (TRIALKYLAMMONIUM AGGREGATES, BILE SALT MICELLES AND MICROEMULSIONS)... 

The fluorescence polarization technique is a very powerful tool for studying the fluidity and orientational order of organized assemblies (see Chapter 8) aqueous micelles, reverse micelles and microemulsions, lipid bilayers, synthetic non-ionic vesicles, liquid crystals. This technique is also very useful for probing the segmental mobility of polymers and antibody molecules. Information on the orientation of chains in solid polymers can also be obtained. 

Separation of antibiotics and cephalosporins can be achieved successfully by CZE because most of them are ionic species. As an alternative to CZE, antibiotics and cephalosporins have been separated by MEEKC. The separation of cephalosporins in different systems (micelles, mixed micelles, and microemulsions) was investigated. The best separation was achieved in microemulsions (Fig. 4). Figure 4 shows that cephalosporins have better affinity to ME in the ME systems than in the MC systems. The affinity of cephalosporins in the ME systems decreases with decrease in the migration time. The MEEKC was also particularly suitable for neutral cephalosporins that could not be separated by CZE or MEKC (14) (see Fig. 5). The method provided good reproducibility and rapid separation with high efficiency. 

Bourrel M, Bernard D, Graciaa A (1984) Properties of binary mixtures of anionic and cationic surfactants Micellization and Microemulsions. Tenside Deterg 21 311-318... 

Zulauf M, Eicke HE (1979) Inverted Micelles and Microemulsions in the Ternary-System H2o-Aerosol-Ot-lsooctane as Studied hy Photon Correlation Spectroscopy. 

Haring, G., Pessina, A., Meussdoerffer, F, Hochkoppler, A., and Luisi, P. L. (1987). Solubilization of bacterial cells in organic solvents via reverse micelles and microemulsions. Ann. Biochem. Eng., 506, 337-344. 

Membrane-mimetic compartments have provided a viable means for generating monodispersed catalytic particles [500], In particular, reversed micelles and microemulsions have been used extensively as hosts. A complete summary of work reported on the in situ generation of catalysts in membrane-mimetic media, including publications up to 1987, has been produced [500] and, therefore, will not be reiterated here. Attention will be focused on more recent research utilizing monolayers, bilayer lipid membranes (BLMs), Langmuir-Blodgett (LB) films, zeolites, and clay particles as membrane-mimetic templates. 

Reversed micelles and microemulsions continue to be used as hosts for the in situ generation of nanosized platinum [539, 540], palladium [539], rhodium... 

Osseo-Asare, K. 1991. Aggregation, reversed micelles and microemulsions in liquid-liquid extraction The tri-n-butyl phosphate-diluent-water-electrolyte system. Adv. Colloid Interface Sci. 37 123-173. 

The use of inverse micelles and microemulsions of AOT in supercritical or near supercritical fluids as extractants for valuable hydrophilic substances such as proteins continues to develop. FT-IR studies of the pressure dependence of the water core structure in various parts of the phase diagrams of such systems have been described (89). 

Zhou N, Li Q, Wu J et al (2001) Spectroscopic characterization of solubilized water in reversed micelles and microemulsions sodium bis(2-ethylhexyl) sulfosuccinate and sodium bis(2-ethylhexyl) phosphate in n-heptane. Langmuir 17(15) 4505-4509... 

Micelles and microemulsions have been explored as membrane mimetic systems since they possess charged microscopic interfaces which act as barriers to the charge recombination process (Fendler et al., 1980 Hurst et al., 1983). Namely, the influence of the location of the sensitizer on photoinduced electron transfer kinetics and on charge separation between photolytic products in reversed micelles has been studied (Pileni etal., 1985). 

---