Inorganic reactions in microemulsions

Spectroscopic studies were performed on water in supercritical CO2 microemulsions using an ammonium carboxylate PFPE surfactant (24). FTIR spec-toscopy was used to identify a bulk water phase within the microemulsion capable of solubilizing ionic species and supporting inorganic reactions. In addition, the UV-visible spectrum of the solvatochromic probe methyl orange indicated three microenvironments within the microemulsions (a) a polar microenvironment like that found in dry PFPE reverse micelles (b) bulk water microenvironment and (c) an acidic microenvironment due to CO2 dissolved in water. 

Although the synthesis of inorganic particles in microemulsions is already widespread, only polymer nanoparticles have been synthesized in microemulsion media as far as the organic particles are concerned. In this chapter, it will be shown that it is also possible to synthesize organic particles by a direct precipitation reaction in the microemulsions. 

However, it is well known that micelle and microemulsion solutions can have a profound effect on reaction rates for organic (1.) and inorganic(2) reactions. In this work we report mechanistic data from microemulsion solutions that would otherwise be Inaccessible. 

It should also be noted that while very few Interfaclad inorganic reactions have been examined in microemulsion media, these studies have shown that this is a fertile field for future investigations. 

Abstract This review describes how the unique nanostructures of water-in-oU (W/0), oil-in-water (0/W) and bicontinuous microemulsions have been used for the syntheses of some organic and inorganic nanomaterials. Polymer nanoparticles of diameter approximately 10-50 nm can easily be obtained, not only from the polymerization of monomers in all three types of microemulsions, but also from aWinsor l-like system. A Winsor 1-like system with a semi-continuous process can be used to produce microlatexes with high weight ratios of polymer to surfactant (up to 25). On the other hand, to form inorganic nanoparticles, it is best to carry out the appropriate chemical reactions in W/0- and bicontinuous microemulsions. 

Clarke et al. showed that W/C microemulsions can be used as a new environment for inorganic chemistry by studying well-known inorganic reactions (78). Roberts et al. have recently demonstrated the production of nano-sized metallic copper particles in AOT reversed micelles in compressed... 

Although microemulsions are of great industrial importance, it is only in recent years that their role as media for organic and inorganic reactions has attracted attention [148-156]. 

The combination of the pseudophase assumption with mass action binding constants of substrates and ion exchange of reactive and nonreactive counterions is called the pseudophase ion-exchange (PIE) model [10,48,66]. It successfully fits the kinetics of many bimolecular reactions and also shifts in apparent indicator equilibria in a variety of association colloids, especially reactions between organic substrates and inorganic ions in normal micelles over a range of surfactant and salt concentrations and types (up to about 0.2 M). It has also been successfully applied to cosurfactant-modified micelles [77,78], O/W microemulsions [79-81], and vesicles [82]. 

Self-assembly systems, from the viewpoint of this chapter, comprise predominantly micellar and microemulsion systems and vesicle assemblies. Most reactions have, however, been studied in micellar systems, and until recently, these were predominantly organic and inorganic processes, although recently there has been considerable work involving enz3rme-catalyzed processes, especially in microemulsion and gel media. Because this topic is now a mature field of study, this chapter will necessarily be selective, and will be mainly focused on the personal interests of the authors. 

Keywords Microemulsion polymerization Microemulsion reaction Water-in-Oil (W/O) microemulsion Oil-in-Water (0/W) microemulsion Bicontinuous microemulsion Functional membranes and inorganic/polymer nanocomposites... 

On the other hand, microemulsion system could combine hydrothermal methodology to enhance the crystallization of NPs. Yan et al. s)mthe-sized t-YVOi NPs by CTAB microemulsion assisted hydrothermal reaction (Sun et al., 2002). As a t)q)ical four-component reverse micelle system, the solution contained surfactant CTAB, cosurfactant n-hexanol, oil phase n-heptane and water phase with inorganic salt. When the W value (the molar ratio of water/CTAB) was below 16, the sizes of NPs could be mediated in the range of 9-50 nm by adjusting the... 

Another type of structurally ill-defined emulsion between water and organic compounds can be applied as an efficient reaction medium for reactions between hydrophilic inorganic salts and hydrophobic organic substrates. So-called microemulsions are particularly useful in the case where the isolation of the reaction products is not necessary. 

Particles may be formed at the inorganic-C02 interface. Inorganic suspensions of metals and metal oxides have been formed by reaction or by mixing particles stabilized by surfactants or ligands (25). Semiconductor nanoparticles have been formed through chemical reduction in water-in-C02 microemulsions. The vast number of potential interfaces formed by combination of hydrophilic, lipophilic, and C02-philic phases will continue to offer... 

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