Dielectric spectroscopy of cosurfactant facilitated percolation in reverse microemulsions

• Published in: The Journal of chemical physics 1999-10, Vol.111 (15), p.7023-7028
• Main Authors: Alexandrov, Yuriy, Kozlovich, Nick, Feldman, Yuri, Texter, John
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.479994

Percolation in reverse microemulsion systems can be driven by various field variables, including temperature and cosurfactant concentration. We use dielectric spectroscopy and a macroscopic dipole correlation function (DCF) derived therefrom to examine mesoscale structural aspects of charge transport in a water, AOT, toluene reverse microemulsion that is driven into percolation by cosurfactant (acrylamide). A multiexponential fitting of the DCF data gives firm support to the importance of a parameter marking the onset of percolation, as distinguished from the percolation threshold. A stretched exponential fitting of the DCF data reveals microstructural and mesoscale similarities and differences between this case of cosurfactant-induced percolation and a previously examined case of temperature-induced percolation. This cosurfactant-driven system appears to exhibit a critical slowing down on approach to the percolation threshold, as does the temperature-driven case, but a much shorter relaxation time suggests the development of much less fractal structure in this cosurfactant case. The effective fractal dimensionality and number of self-similarity stages of the fractal structure are only weak functions of the reduced field variable in the case of cosurfactant-driven percolation, and contrast sharply with the temperature case.