MODELING THE ELECTRIC BIREFRINGENCE RELAXATIONS OF AOT/ISOOCTANE/H2O WATER-IN-OIL MICROEMULSIONS

The dynamic behavior and equilibrium properties of reverse micelles and water-in-oil microemulsions of the AOT/isooctane/H2O system were investigated in a wide region of the homogeneous L(2) phase, far from the boundary separating the L(2) and L(2) + LC (liquid crystalline) phases. The electric square pulse induced transient birefringence of the ternary systems revealed two distinct relaxation processes. The fast process is attributed to the creation of aligned micellar induced dipoles, and the slow process to the growth and linearization of micellar clusters, in the direction of the applied field. The forward (in field) and backward (zero field) relaxation rates were found to be equal within experimental error. The relaxation rates, however, diminish, while the viscosity increases, with increasing surfactant concentration [AOT], temperature, and the molar ratio of water to AOT, R drop [H2O]/[AOT]. These effects are discussed in relation to the proposed equilibrium and dynamic description of the system.