Mikroemulsion

A mikroemulsion is a thermodynamically stable, optically isotropic dispersion of oil and water, stabilized by a sufficient amount of surfactant and often a co-surfactant. Unlike conventional emulsions, which are typically kinetically stable and appear opaque, mikroemulsions are clear and form spontaneously at room temperature without significant energy input. They possess very small droplet sizes, typically in the range of 10 to 100 nanometers.

The stability of a mikroemulsion arises from the low interfacial tension between the oil and water phases, achieved by the surfactant molecules. These molecules orient themselves at the interface, reducing the repulsive forces between the immiscible liquids. The co-surfactant, often a short-chain alcohol, helps to further lower the interfacial tension and increase the fluidity of the surfactant film, promoting droplet formation and stability.

Mikroemulsions can exist in various structures depending on the relative amounts of oil, water, and surfactant, including oil-in-water (o/w), water-in-oil (w/o), and bicontinuous phases. The specific structure is determined by the phase behavior of the system, which can be represented by phase diagrams.

Due to their unique properties, such as large interfacial area, high solubilization capacity, and thermodynamic stability, mikroemulsions find applications in diverse fields. These include drug delivery systems, where they can enhance the solubility and bioavailability of poorly soluble drugs, as well as in cosmetics, food processing, and enhanced oil recovery. Their ability to solubilize both oil and water components makes them versatile systems for various industrial and scientific purposes.