Chemical reactions, microemulsion facilitation

In addition to being a fundamental consequence of the nature of amphiphilic molecules, micelle formation also plays a significant part in the practical application of surfactants in various areas. Because they represent what might be considered a second liquid phase in solution, micelles are often found to facilitate the production of apparently stable, isotropic solutions of normally insoluble liquids and sometimes solids, quite distinct from the obviously two-phase emulsions and sols previously discussed. Depending on the system (and the observer), such solutions are said to result from either solubilization of a material in the continuous phase or from the formation of microemulsions. In addition, the unique character of the micelle makes it a potentially useful transition zone between phases in which the unique environment may facilitate (i.e., catalyze) chemical reactions difficult to achieve under normal two-phase conditions. The ability of a surfactant to carry out such functions is of great potential importance and warrants some closer attention. 

A microemulsion is a thermodynamically stable three-component system two immiscible components (generally water and oil) and a surfactant molecule that lowers the interfacial tension between water and oil resulting in the formation of a transparent solution. Water-in-oil microemulsions involve dispersion of the aqueous phase as nanosized droplets (5-25 nm in diameter) surrounded by a monolayer of surfactant molecules in the continuous hydrocarbon phase. These micellar droplets exhibit a dynamic exchange of their contents, which further facilitates the reactions between reactants dissolved in different droplets. One can synthesize size-controlled crystallites by carrying out a wide variety of chemical reactions in nanodroplets using this micellar exchange. Different types of microemulsions are... 

Microemulsions also facilitate and control heterogeneous chemical reactions. Examples include, hypochlorination reactions of water insoluble liquid reactants in microemulsion reaction media produced industrially useful epoxides and epoxide derivatives in high yields (107). Many other microemulsion-based reaction systems were described by Hager (108), including bioorganic reactions in microemulsions (109), metal nanoparticle synthesis in water-in-oil microemulsion (110), as well as polymerization within microemulsions and other self-organized media (111). 

Microemulsion is used as a special microreactor to limit the nano-sized particles growth. The shape of the microreactor depends on reaction conditions [9]. This method increases the homogeneity of the chemical composition at nano-level and facilitates the preparation of nano-particles with comparatively equal sizes [11]. The specific properties of the nano-particles make them suitable for microelectronics, ceramics, catalysis, medicine, cosmetics, as piezoelectric materials, conductors, etc. 

---