Nano-emulsions functional characteristics

In this chapter, nano-emulsion formation by low-energy emulsification methods, with special emphasis on phase inversion methods and their relation to surfactant phase behavior will be discussed first. This will be followed by an analysis of nano-emulsion functional characteristics. The relation with their structure is discussed regarding the applications in which they are relevant. Prior to discussing nano-emulsion functional characteristics, the main nano-emulsion destabilization mechanism, Ostwald ripening, is described. 

The majority of publications on nano-emulsions emphasize their potential applications, comparing them with conventional emulsions (macroemulsions) and microemulsions. With respect to macroemulsions, the main advantage of nano-emulsions would be the smaller droplet size, whereas with respect to microanulsions the main advantage would be the lower amount of surfactant needed for their stabilization. The possibilities of developing applications are mainly limited by stability [2], which is of conrse related to the structure of nano-emulsions, and can be considered a functional characteristic. On the other hand, the potential applications of nano-emulsions depend on their functional characteristics. 

In this section, the functional characteristics of nano-emulsions and the relation with their structure are analyzed and discussed in relation to the applications in which these functional characteristics can be important. The section is divided according to the main functional characteristics determining the applications of nano-emulsions stability, droplet size, and solubilizing capacity. 

As a partial conclusion of this subsection, influence of droplet size of nano-emulsions on their functional applications would depend on the very specific characteristics of application and on the system used. Consequently, each system should be specifically studied. It may seem that extensive experimental study should be needed for each new application based on droplet size. However, the accumulated knowledge that can be extracted from experimental published work, especially in the recent years, should allow theoretical predictions about the influence of droplet size and savings in experimental work. 

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