Thermal actuation properties of bimorph based on PVDF/rGO composites

Our study describes the fabrication of thermal actuation with a bimorph film of PVDF/rGO composites and polyimide film, exploiting the large difference in the thermal expansion coefficients of the two films. We performed the thermo-mechanical and XRD characterization of the obtained PVDF/rGO composites. The analyses indicate that the novel composites have enhanced mechanical strength and higher portion of β-phase crystallinity as compared to those of pure PVDF. To fabricate the bimorph for thermal actuation, the solution of PVDF/rGO composites is simply casted on a polyimide film. Thereafter, we evaluate their mechanical displacement using a temperature stimulus. However, in case of pure PVDF sample, a limited and permanent displacement is observed when subsequent cycles of thermal actuation test are performed, the PVDF/rGO samples exhibit a superior controlled displacement as they regained their original shape completely, even after being subjected to the repeated heating/cooling cycles. On the basis of control experiments and XRD study, the possible mechanism is suggested that the PVDF/rGO composites show excellent characteristics of thermal actuation as they are associated with a reversible transformation of crystalline phase and the enhanced mechanical strength in the presence of rGO in the composites.