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Microemulsions are clear, thermodynamically stable, isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be a complex mixture of different hydrocarbons and olefins. In contrast to ordinary emulsions, microemulsions form upon simple mixing of the components and do not require the high shear conditions generally used in the formation of ordinary emulsions. The three basic types of microemulsions are direct (oil dispersed in water, o/w), reversed (water dispersed in oil, w/o) and bicontinuous. In ternary systems such as microemulsions, where two immiscible phases (water and ‘oil’) are present with a surfactant, the surfactant molecules may form a monolayer at the interface between the oil and water, with the hydrophobic tails of the surfactant molecules dissolved in the oil phase and the hydrophilic head groups in the aqueous phase. ==Uses== Microemulsions have many commercially important uses: * Water-in-oil microemulsions for some dry cleaning processes * Floor polishers and cleaners * Personal care products * Pesticide formulations * Cutting oils * Drugs〔(Gibaud S, Attivi D (2012) Microemulsion for oral administration and their therapeutics applications.Expert Opin Drug Delivery Jun 5. [Epub ahead of print] )〕 Much of the work done on these systems have been motivated by their possible use to mobilize petroleum trapped in porous sandstone for enhanced oil recovery A fundamental reason for the uses of these systems is that a microemulsion phase sometimes has an ultralow interfacial tension with a separate oil or aqueous phase, which may release or mobilize them from solid phases even in conditions of slow flow or low pressure gradients. Microemulsions also have industrial applications, one of them being the synthesis of polymers. Microemulsion polymerization is a complex heterogeneous process where transport of monomers, free radicals and other species (such as chain transfer agent, co-surfactant and inhibitors) between the aqueous and organic phases, takes place.〔"A Microemulsion Process for Producing Acrylamide-Alkyl Acrylamide Copolymers", S. R. Turner, D. B. Siano and J. Bock, U. S. Patent No. 4,521,580, June 1985.〕 Compared with other heterogeneous polymerization processes (suspension or emulsion) microemulsion polymerization is a more complicated system. Polymerization rate is controlled by monomer partitioning between the phases, particle nucleation, and adsorption and desorption of radicals. Particle stability is affected by the amount and type of surfactant and pH of dispersing medium.〔Ovando V.M. Polymer Bulletin 2005, 54, 129-140〕 It is also used in the process of creating nanoparticles. The kinetics of microemulsion polymerization has much in common with emulsion polymerization kinetics, the most characteristic feature of which is the compartmentalization, where the radicals growing inside the particles are separated from each other, thus suppressing termination to a high extent and, as a consequence, providing high rates of polymerization. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「microemulsion」の詳細全文を読む スポンサード リンク
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