Influence of co-surfactants on microemulsions with alkyl polyglycosides

Microemulsions are isotropic, thermodynamically stable systems consisting o f surfactant, oil and water and, if necessary, additives such as alcohols o r electrolytes. They can be obtained with emulsifier systems based on ethox ylated nonionic surfactants in a certain limited temperature range. If alky l polyglycosides are used as surfactants, only a slight temperature depende nce can be observed. In this case, the formation of microemulsions depends on the ratio of hydrophilic to lipophilic components in the surfactant syst em. Although there have been many studies regarding different oil/water/emu lsifier systems, the formulation of microemulsions with optimal properties still depends on time-consuming empirical tests. The systematic investigation of the phase behavior of specifically selected systems is the basis for the development of emulsions for practical purpos es. In this study, the phase behavior of model microemulsions consisting of an alkyl polyglycoside as hydrophilic emulsifier, a lipophilic co-emulsifi er, an oil component and water is discussed. In particular the effects of d ifferent co-emulsifiers on the interface and therefore the formation and st ability of microemulsions are assessed and interpreted. It turns out that a n emulsifier system consisting of C-12/14 alkyl polyglycoside and glyceryl monooleate facilitates the formation of stable microemulsions very effectiv ely. (C) 1998 Elsevier Science B.V. All rights reserved.