Effect of Micelle Size on the Dielectric Relaxation and Dynamic Behavior of Reverse Micelles Using the Open-Ended Coaxial Line Technique

摘要

A model system was used to study the molecular dynamics and transport of macromolecules, which are very often characterized by their confined state. This complex model consisted of a ternary mixture (reverse micelles) composed of the surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT), H_2O and isooctane (C_8H_(18)) as the apolar, oil phase. The dielectric parameters of this system were investigated using the open ended coaxial line method. The high frequency response of the AOT reverse micelles was characterized over a frequency scale from 10MHz to 20 GHz, as a function of the waterto-surfactant ratio (W_0) and the surfactant-to-oil ratio (Φ_m) at room temperature, 298 K. Measurements of the complex permittivity of this AOT/C_8H_(18)/H_2O system are reported. The experimental values of the real part of the complex permittivity of the AOT reverse micelles were fitted by the Havriliak-Negami function emphasizing the reverse micelles size effect; these measurements were sufficient to give us important information about the dynamic behavior of the AOT reverse micelles dispersed in isooctane. In the frequency range studied three different motions were identified as functions of the reverse micelle size (R_w).