Electromechanical performance of polydimethylsiloxane containing reduced graphene oxide grafted by long-chain alkyl silane

The present study investigates the effects of grafting a long-chain organosilane (OS) onto the reduced graphene oxide (rGO) on dielectric and electromechanical performance of polydimethylsiloxane (PDMS). Accordingly, two types of OS-rGO particles were synthesized with different grafting densities and characterized by various tests such as Fourier transform infrared spectroscopy, Raman spectroscopy, and thermo-gravimetric analyses. As-prepared particles were introduced into PDMS using the solution mixing method to manufacture composites with different concentrations of particles. Dielectric results revealed that the composites containing OS-rGO particles offer better dielectric performance in terms of higher dielectric efficiency and dielectric breakdown strength than composites containing rGO or neat PDMS. The higher the grafting density of OS, the better the dielectric and electromechanical performance is obtained. By examining the electrical conductivity of particles, it was discussed that the spacer length of silane creates a space-filling insulating layer around the conductive rGO particles, traps free electric charges at the particle-polymer interface, postpones the electrical percolation threshold to higher concentrations, and reduces the dielectric loss through suppressing the leakage current of charges in the composite. Actuation strain of PDMS containing 3 wt% of OS-rGO with high grafting density was almost twice that for the neat PDMS.