RHEOLOGICAL MODELLING OF MICROEMULSIONS.

Microemulsions are original dispersions, thermodynamically stable, transparent and very fluid. Their main properties are reviewed, with special emphasis on their rheological behavior. Viscosity properties, in particular, are known to depend strongly on microstructural changes. Viscosity peaks are found close to percolation-like transitions. A Krieger-type formula has been used to model the viscosity variations in a well-known model system where structural changes are induced by salinity variations. The variations of the effective packing volume fraction follow current expectations and reveal, for well-defined values of the salinity, the formation of droplet clusters, coalescence in the clusters, and the appearance of bicontinuous structures. Interpreted in this way, the viscosity data give a very useful insight into the mechanism of microstructural changes in microemulsions and will be helpful in achieving a better understanding of their properties.