structures. They can be spherical (Figure 1-6), spheroidal, or cylindrical "rod" or "worm-like"

micelles, and they may exist in hexagonal, cubic, or lamellar phases. Alternatively, a range of

bicontinuous phases may exist.















Figure 1-6. Structure of normal (left) and inverse (right) spherical micelles formed in
 microemulsion systems.

 Microemulsions can have characteristic properties such as ultra low interfacial tension,

large interfacial area and capacity to solubilize both aqueous and oil-soluble compounds.'o

Therefore, they can be used in a variety of applications, for example in enhanced oil recovery,"

as fuels,52 as lubricants, cutting oils, and corrosion inhibitors,53 as coatings and textile finishing,54

in detergency," in cosmetics,56 in food,57 in pharmaceuticals,58 or in biotechnology.59 As

presented in Chapter 6, an oil-in-water microemulsion system composed of spherical micelles

was designed in an attempt to selectively encapsulate hydrophobic toxic drugs inside the micellar

oil core and to decrease their free concentration in the blood stream. Even though microemulsion

systems are thermodynamically stable, the high dilution taking place after their injection inside

body fluids would lead to rupture and further coalescence of the micellar structures. This

problem can be avoided by building a solid shell surrounding the microemulsion oil droplets that

will not break upon dilution, for instance by the means of Sol-Gel chemistry (hence the name

core-shell nanocapsules).