Dielectric properties of dielectrophoretically assembled particulate-polymer composites

The dielectrophoretic effect is a phenomenon in which dipole-dipole interactions are induced between particles in a suspension by an electric field.^1-5 This dipole interaction leads to the formation of chains or fibrils parallel to the applied electric field Recently the dielectrophoretic effect has been shown to be a possible composite assembly technique permitting property changes to be induced with the appropriate electric fields.^6,7 The results presented in this paper show that the dielectrophoretic assembly process can be used to engineer anisotropy into composite materials. Various filler materials are aligned in a thermoset polyurethane matrix and the dielectric properties are measured Comparisons are drawn between the dielectrophoretically assembled composites and those processed conventionally in the absence of an electric field. Dielectric properties are modeled with modified mixing laws and discussed in relation to the composite microstructure and the alpha relaxations of the polymer phase.