Effect of Free and Bound Water on the Dielectric Properties of Non-ionic Microemulsions

The effects of free and bound water on the dielectric properties of microemulsions prepared with the non-ionic surfactant Brij 97 were investigated. For the calculation of the relative amounts of free and bound water, a simple multi-layered dielectric model was applied. The model considers the microemulsion as a sum of three separate layers consisting of a 'dry' microemulsion, free water and bound water, respectively. The method is based on dielectric measurements of microemulsions at a frequency for which the dielectric permittivity and the dielectric losses for bound and free water have significantly different magnitudes. The dielectric contribution of free water to the relaxation spectrum of the microemulsion can be obtained, allowing both fractions to be calculated. In contrast to the traditional procedures used for calculation of bound water from the relaxation spectrum, this method does not involve analyses of overlapping relaxation processes.