Abstract:

The dielec. spectroscopy method (DS) has become a useful technique for the investigation of the structural and dynamic features of the components of both microemulsions and microdroplets over a wide temp. and frequency range. The dielec. parameters obtained by DS det. the geometry of the assocn. structures as well as the overall picture of the dynamics of the different polar groups. aggregates, and assocn. structures representing dipole modes. In this paper the results of a comprehensive study of the different types of microemulsions (ionic and nonionic) DS are presented. The static and dynamic dielec. properties of microemulsions a a function of temp., frequency and concn. of water, oil, surfactant and cosurfactant are considered. The dielec. properties have been investigated in the frequency range 105-1010 Hz using time domain dielec. spectroscopy (TDDS) and over a broad temp. interval enabling us to cover all the man dynamic processes occurring in such systems. The data treatment for the dynamic behavior of the microemulsions was carried out in the time domain in terms of dipole correlation functions and in the frequency domain in terms of complex dielec. permittivity. The correlation functions of the investigated systems exhibit complex nonexponential relaxation behavior, which must be deconvolute into normal modes and represented as a sum of the simple exponential, exp(-t/$\tau$), and nonexponential terms, exp[-(t/$\tau$)v]. The parameter $ν$ characterizes the shape of the relaxation function and the cross-correlation effects, and describes the morphol. of the system. The mol. mechanisms responsible for dielec. polarization in microemulsion of different nature at discussed. Knowledge of the amt. of hydrate water and co-surfactant in the interface can be obtained for nonionic microemulsions. In the case of ionic microemulsions, TDDS is a powerful technique for monitoring the organization of clusters and for investigation of relaxation processes involving rearrangement and movement of the droplets forming the clusters. [on SciFinder(R)]