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Mesoscopic Non-Equilibrium Thermodynamics Part 14

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Tham khảo tài liệu 'mesoscopic non-equilibrium thermodynamics part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 18 Microemulsions Thermodynamic and Dynamic Properties S.K. Mehta and Gurpreet Kaur Department of Chemistry and Centre of Advanced Studies in Chemistry Panjab University Chandigarh India 1. Introduction Mixing two immiscible liquids such as oil and water using emulsifier and energy inputs has been the matter of study for decades. In early 1890 s extensive work have been carried out on macroemulsions i.e. oil dispersed in water in the form of fine droplets or vice versa Becher 1977 and several theories and methods of their formation have been vastly explored Lissant 1976 and 1984 . However going along the line microemulsion systems were well opted because of their stability and isotropic nature. Microemulsions are basically thermodynamically stable isotropically clear dispersions of two immiscible liquids such as oil and water stabilized by the interfacial film of any surfactant and or cosurfactant. Although a microemulsion is macroscopically homogeneous or quasi-homogeneous but structured microscopically. Microemulsions in comparison to micellar systems are superior in terms of solubilization potential and thermodynamic stability and offers advantages over unstable dispersions such as emulsions and suspensions since they are manufactured with little energy input heat mixing and have a long shelf life Constantinides 1995 . The term microemulsion was first coined by Schulman group Schulman et al. 1959 . However ambiguity in the microemulsion terminology persists till today as some authors differentiate them from swollen micelles which either contain low volume fraction of water and oil and transparent emulsions Prince 1977 Malcolmson et al. 1998 . One of the unique factors associated with microemulsions is the presence of different textures such as oil droplets in water water droplets in oil bicontinuous lamellar mixtures etc. which are formed by altering the curvature of interface with the help of different factors such as salinity temperature etc. Such a variety in