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Dielectric Relaxation in a Water−Oil−Triton X-100 Microemulsion near Phase Inversion

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journal contribution
posted on 27.09.2005, 00:00 by Koji Asami
A mixture of water (10 mM KCl), toluene and Triton X-100 (40:40:20 wt %) shows temperature-dependent phase inversion. The phase inversion has been studied by dielectric spectroscopy over a frequency range of 10 Hz to 1 GHz. At temperatures above about 37 °C, dielectric relaxation appeared around 10 MHz, which was due to interfacial polarization in a water-in-oil type emulsion. The dielectric relaxation drastically changed between 30 and 25 °C. With decreasing temperature, the intensity of dielectric relaxation increased steeply below 30 °C to attain a peak at 27 °C, where that change was associated with an increase in low-frequency conductivity by about three orders between 30 and 26 °C. The dielectric behavior has been interpreted in terms of interfacial polarization with a percolation model in which spherical water droplets, arranged in array in a continuous oil phase, are randomly connected with their nearest neighbors using water bonds.