Study of a critical ternary microemulsion by permittivity and Kerr-effect techniques

摘要

A critical microemulsion (AOT/decane/water, W-0=34.6 and phi(g)=0.068) was studied using complex permittivity and Kerr-effect techniques. Permittivity measurements were made in the range from 150Hz to 1.5 MHz using a circuit of a novel design. Below 100 kHz a dielectric relaxation process appears, it can be related to a Maxwell - Wagner polarization effect. Moreover, the conductivity has a clearly critical behavior in agreement with references in the literature. On the other hand, measurements of static and dynamic electric birefringence near to the critical temperature show a diverging Kerr constant and a strong asymmetry between a rise and decay of birefringence, similar to those described by Degiorgio and Piazza for similar systems [V. Degiorgio, R. Piazza. Phys. Rei. Lett., 55(3), 288 (1985)]. Results are explained by assuming that the microdroplets do not change their shape but form clusters near the critical temperature. The critical exponents agree quite well with the information found in the literature for similar systems [Letamendia, E. Pru-Lestret, P. Panizza, J. Rouch, F. Sciortino, P. Tartaglia, C. Hashimoto, H. Ushiki, D. Risso. Physica A, 300, 53 (2001)].