LOCAL POROSITY THEORY FOR THE FREQUENCY-DEPENDENT DIELECTRIC FUNCTIONOF POROUS ROCKS AND POLYMER BLENDS

We report preliminary results for the application of local porosity th eory to dielectric response measurements on two classes of inhomogeneo us systems. One class of systems are mixtures of insulators and conduc tors realized experimentally as sintered glass bead porous media satur ated with salt water. In this case the response arises from the Maxwel l-Wagner effect. The second class are mixtures of insulators realized experimentally in polymer blends where the response arises from the re laxation of atomic or molecular dipole moments. For the case of water saturated sintered glass bead systems two-dimensional local porosity d istributions have been determined from digital image analysis. These m easurements allow for the first time semiquantitative comparisons to p revious theoretical approaches and with experiment. The dielectric mea surements are used to extract the total fraction of percolating cells in the mixture. For the polymer case we show that recent concentration fluctuation models for the dielectric alpha-relaxation arise as speci al cases of local porosity theory. Furthermore it is exemplified how i nformation from static Monte-Carlo simulations of polymer blends may b e useful in comparing theoretical calculations to experiment.