Dielectric properties of silicone rubber-titanium dioxide composites prepared by dielectrophoretic assembly of filler particles

Formation of a controlled morphology of fillers in polymeric composites may be difficult to achieve by conventional methods such as mechanical shear or chemical methods. A tunable structure of filler and anisotropic properties in composites can be obtained by exploiting dielectrophoretic assembly of fillers in a polymer composite by using electric fields. In this study, different concentrations of titanium dioxide (TiO2) particles in silicone rubber matrix were assembled in a chain-like structure by using an alternating electric field. The silicone rubber matrix was vulcanized to transform the liquid to solid and maintain the filler structure in the desired direction. Generation of the chain structure of the filler was verified by scanning electron microscopy (SEM) and equilibrium swelling. It was shown that dielectric permittivity of the oriented composite is higher whereas its dielectric loss is lower in the orientation (thickness) direction than those for composites with random distribution of filler. A critical concentration of filler was distinguished as the percolation point at which the change in dielectric behavior is amplified.