Preparation and enhanced electro-responsive characteristic of reduced graphene oxide/polypyrrole composite sheet suspensions

We used reduced graphene oxide (RGO) as a core to prepare core-shell-structured RGO-supported polypyrrole composite dielectric sheets and demonstrated that the composite sheets possessed significantly enhanced electro-responsive electrorheological (ER) characteristic compared to conventional granular polypyrrole. The morphology and structure were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier-transform infrared spectra. The ER characteristic of the sheets when dispersed in silicone oil was investigated by rheological tests under external electric fields. It showed that the shear yield stress of the sheet suspension was significantly higher than that of a suspension containing conventional granular polypyrrole at the same electric field strengths. A complex flow behavior was observed in the sheet suspension, which was different from the Bingham flow behavior in the granular polypyrrole suspension. The sheet suspension also showed higher field-shear moduli and two viscoelastic plateaus as a function of applied stress amplitude. The enhanced ER response was analyzed by the dielectric data and optical microscopy image of the ER structure.