ABSTRACT
Microemulsions are spontaneously forming, thermodynamically stable, homogeneous low viscous, and optically isotropic solutions. These macroscopic homogeneous mixtures are heterogeneous on a nanometer scale [1-4]. Reverse or inverse microemulsions have nanoscopic water droplets dispersed in a
pseudocontinuous phase of oil, and the low radius of curvature in this case has opposite sign to the radius of curvature in the oil-in-water (o/w) example. Due to their unique properties, microemulsions have been used in a variety of technological applications, including environmental protection, nanoparticle formation, personal care product formulations, drug delivery systems, and chemical reaction media [5-10]. In most industrial applications, the use of mixed surfactants system is preferred over the use of pure surfactant-based systems [11]. The determinations of the phase behavior of water/mixed surfactants/oil system quantitatively is of eminent signifi cance for further investigation and possible applications. The study of the phase behavior of mixed nonionic surfactants in water and oil demonstrated that the amount of surfactants present at the wateroil interface determines the extent of water and oil mutual solubilization [12-16]. This amount of surfactants depends on factors like surfactant’s chemical structure and hydrophilicity, the monomeric solubility of surfactants in oil and water, and the presence of additives. It was found that the water-in-oil (w/o), solubilization increases dramatically when nonionic surfactants, whose hydrophiliclipophilic balances are far separated, are mixed [12-16]. At constant temperature, the hydrophilic-lipophilic balances of mixed surfactants in surfactants monolayers inside the microemulsion are the same in the case where oil is fi xed. It was also found that the total surfactant concentration needed to solubilize an equal amount of water and oil increases with the increase in the lipophilicity (molecular weight) of the oil [12-16]. Diverse and complex dynamics that are highly dependent on the system thermodynamics (i.e., composition and the resulting microstructure) and the dynamics of the constituent molecules are exhibited by microemulsions [1,4,17]. The structure of microemulsions can be idealized as a set of interfaces dividing polar and apolar domains. Mixtures of water, oil, and surfactant exhibit a rich variety of microstructures, ranging from spherical micelles, rodlike micelles, and bicontinuous micro emulsions to ordered liquid crystalline phases. Depending on the composition of the system of oil, water, and surface-active agent(s), the microstructure of a microemulsion may exist as w/o droplets, o/w droplets, or a bicontinuous structure [18-27]. Understanding of the microemulsion’s properties is needed for any scientifi c or industrial application of these systems; thus much work has been done over the last decade in this particular area [28-35]. Various techniques have been employed for this characterization, including electrical conductivity, dynamic viscosity, ultrasonic velocity, light scattering (dynamic and static), pulsed fi eld gradient nuclear magnetic resonance (NMR) spectroscopy, small-angle scattering (SAS) methods, and others [36-51]. In this review paper, we report on the formulation and properties of newly formulated microemulsions of important potential applications including food, pharmacy, nanoparticles technology, and chemical and biochemical synthesis [52-57]. These systems are composed of water/sucrose laurate/ethoxylated monodi-glyceride/oil. The chemical structures of the components used are presented in Figure 5.1.
