THEORETICAL BEHAVIOUR OF MICROEMULSIONS GEOMETRICAL ASPECTS, DILUTION PROPERTIES AND ROLE OF ALCOHOL.COMPARISON WITH EXPERIMENTAL RESULTS.

ABSTRACT

A theoretical model of microemulsions is developped : using the idea of pseudophases, and therefore equilibrium between them, the behaviour of microemulsions can be depicted correctly (geometrical and composition parameters are obtained). The particular role of alcohol is interpreted by means of its autoassociation in the organic pseudophase and its partition between core, membrane and continuous phase of the microemulsion. The four equilibrium constants introduced in the model can be deduced from simple experiments on the ternary system (without surfactant) and from the dilution of only one microemulsion. Experimental results are given for the system water, toluene, S.D.S., nbutanol in order to obtain these four constants. Using them, the model allows the authors to interpret quantitatively the experimental results obtained in a wide region of the phase diagram. In particular, the constancy of membrane composition is related to the autoassociation of alcohol which seems to play a very important role in microemulsion behaviour and for stability.