Dielectric elastomers are highly deformable smart materials capable of actuation under electric fields [1,2]. To study the effect of organically modified Montmorillonite (OMMT) on dielectric properties of silicone rubber as a commercially available dielectric elastomer, OMMT was added to this rubber at two levels of 2% and 5% using high shear mixing. Composites were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The XRD patterns showed that ordered crystallite structure of clay loses its ordered structure leading to disappearance of diffraction peaks. SEM and AFM micrographs depicted good dispersion and uniform distribution of the organo-clay. Tensile properties and dielectric properties of the composites were measured under AC electric fields, and results were compared with the reference silicone rubbers with no OMMT. It was shown that storage and loss dielectric constants of base silicone rubber increase when it is compounded with OMMT.

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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 (TiO 2 ) 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.

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