Tuning the Surface Chemistry of Graphene Oxide for Enhanced Dielectric and Actuated Performance of Silicone Rubber Composites

The influence of reduction temperature on the electromechanical properties and actuation behavior of polydimethylsiloxane (PDMS) dielectric elastomer containing the thermally reduced graphene oxide (rGO) with different surface chemistry has been systematically investigated. A set of rGO nanosheets was prepared by thermal reduction of graphene oxide (GO) at four temperatures (150, 200, 300, and 400 °C). The dielectric permittivity, dielectric loss, and elastic modulus of PDMS composites were increased, while the electrical breakdown strength of composites was decreased with an increase of the reduction temperature of GO. A thermodynamic model applied for studying the electromechanical deformation and stability of PDMS/GO­(rGO-x) dielectric elastomer composites showed that the optimum value of the break-point was observed in PDMS/rGO-300. It is shown for the first time that the variation of electromechanical instability and recovery behavior are attributed to the surface chemistry of rGOs. A critical reduction temperature is observed at 300 °C which can be considered as proper rGO nanosheets for electromechanical applications. By employing an equivalent circuit on impedance spectroscopy, the interfacial polarization is recognized as the dominant mechanism rather than the intrinsic polarization of the matrix and nanosheets. Noteworthy, PDMS composites containing rGO, reduced at higher temperatures, have more interfacial polarized charges at the interface.