Dynamics of structure changes in water-in-oil microemulsions: Electric birefringence and electric light scattering in percolating systems

• Published in: Journal of molecular liquids 1997-08, Vol.72 (1), p.295-314
• Main Authors: Schlicht, Lutz, Spilgies, Jan-Hendrik, Ilgenfritz, Georg
• Format: Article
• Language: English
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/S0167-7322(97)00043-3

Perturbation of a water-in-oil microemulsion system by electric field pulses and simultaneous measurement of electric current, light scattering, and birefringence on a micro- to millisecond time scale allows for structural elements and dynamical processes of these compartmentalized systems to be characterized in detail. Both optical methods probe different modes of dynamics. Whereas light scattering only indicates aggregation of larger clusters, the Kerr effect probes local structure changes as well as changes on a mesoscopic scale. At ranges below well-defined critical fields, deformation of droplets and rearrangement of droplets in clusters can be observed. Above such critical values, the field itself causes structure changes resulting in ‘electric field-induced percolation’. The Kerr effect results provides strong evidence that the droplet structure is maintained in percolating clusters. The surfactant monolayer bending constant changes by about a factor of 150 when the system's temperature passes the percolation transition. There are no principal differences in the properties of microemulsions stabilized by the ionic AOT or the non-ionic Igepal surfactant.