Microemulsion colloidal domain

D. Fennell Evans is the director of the Center for Interfacial Engineering and professor of chemical engineering and materials science at the University of Miimesota. He is the author of more than 180 publications on self-assembly processes in water and nonaqueous solvents, microemulsions, diffusion in liquids and micellar solutions, and characterization of surfaces using scanning probe techniques. He has published two textbooks. The Colloidal Domain and The Fundamentals of Interfacial Engineering. 

Microemulsion systems with their inner structure in the colloidal domain have been the subject of many theoretical and experimental studies due to their very broad applicability [1 ]. The name microemulsion was first introduced by Hoar and Schutman in 1943 as the name for a clear or transparent system obtained by titration of a milky white emulsion with a medium-chain length alcohol (e.g., 1-pentanol or 1-hexanol) [5]. A more general definition of the term microemulsion was given later by Danielsson and Lindman, who described it as a system, composed of water, oil and an amphiphilic component, being an optically isotropic and thermodynamically stable liquid solution [6],... 

The influence of sodium acetate on the phase equilibria of acrylamide microemulsions has been investigated (Holtzscherer, C. Candau, F. J. Colloid Interface Sci., in press). The interfacial tensions of the systems preequilibrated are reported versus the salt concentration in Figure 6. It can be seen that addition of sodium acetate induces a phase transition HI - H III which occurs for S = 1.2H. The intercept of the two curves which occurs in the Vinsor III domain defines an optimal salinity for the formation of bicontinuous microemulsions. 

Heterophase processes should be primarily distinguished based on their emulsion structure (oil-in-water or water-in-oil) and type of stability (kinetic or thermodynamic). This identifies four mutually independent polymerization regimes, each with unique colloidal and chemical behavior. L Macroemulsion, II. Inverse-Macroemulsion, HI. Microemulsion, IV. Inverse-Microemulsion. The macroemulsion and inverse-macroemulsion domains can be further subdivided into Suspension (la), Emulsion (lb), Inverse-suspension (Ha) and Inverse-emulsion (lib) subdomains based on a transition at the critical micelle concentration. 

To overcome most of solubilization problems, colloidal surfactant systems (e.g. micelles, liquid crystals, microemulsions, vesicles, emulsions, etc.) are attracting a great deal of attention as alternative reaction media (Walde 1996 Holmberg 1997 Antonietti 2001). Their advantages are they possess micro- and nanostmctures consisting of well-defined hydrophilic and lipophilic domains separated by surfactant films with very large interfacial area, the exchange between chemical species... 

Information about the bound water fraction in some colloid systems, silica gels, and biological systems is usually inferred on die basis of the frequency- and time-domain DS measurements from the analysis of the dielectric decrements or die relaxation times (64, 150-152). However, the nonionic microemulsions are characterized by a broad relaxation specfrum as can be seen from the Cole-Cole plot (Fig. 33). Thus, these dielectric methods fail because of the difficulties of deconvoluting die relaxation processes associated widi the relaxations of bound water and surfactant occurring in the same frequency window. 

In colloidal research, it has been often found that ILs are employed as polar and nonpolar domains moreover, they can even serve as amphiphilic components in the formation of microheterogeneous assemblies like micelles, microemulsions, etc. 

The development of novel polymer latex particles, especially in the domain size lower than 100 nm, makes them very attractive, for instance, in nanotechnologies and bionanotechnology (which combines biosystems and nanofabrication). At first, innovating heterogeneous polymerization techniques such as those taking place in surfactant assemblies (microemulsions, vesicles etc.) or using polymerizable amphiphiles should provide polymer colloids with unexpected properties. In addition, the possibility to associate organic and... 

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