Dielectric properties of dielectrophoretically aligned ZNO-PDMS composites

ZnO based polymer composite materials are of great interest because of their excellent electrical, optical, semiconductor and biocompatible properties. In this study, we synthesize anisotropic composites of aligned ZnO rods in polydimethylsiloxane (PDMS) elastomer and study their dielectric properties as a function of applied electric field and frequency. Submicron ZnO rods are synthesized using an inexpensive, high yield chemical route. Washed and purified ZnO rods are then aligned in uncured PDMS at different electric field and frequency. We find that under electric field, ZnO rotates with their long axis in the direction of the electric field and before coalescing form chains in the silicone elastomer. From the optical microscopy images and in situ dielectric measurements, the best alignment parameters are found at 4 kV/mm and 10 kHz. These conditions are then selected to prepare aligned ZnO-PDMS composites. Complete curing of composites is confirmed using dynamic mechanical analysis (DMA). Our results show that aligned ZnO in uncured PDMS exhibit higher dielectric permittivity compared to random dispersion with the same composition. For the cured ZnO-PDMS composites, dielectric permittivity increases by 80% compared to random composites.