Graphene oxide coated core-shell structured polystyrene microspheres and their electrorheological characteristics under applied electric field

Core-shell structured polystyrene (PS)-graphene oxide (GO) microspherical particles were synthesized by adsorbing the GO sheets on the PS surface through a strong pi-pi stacking interaction. As core materials, monodispersed PS microspheres were prepared using a dispersion polymerization, while the shell part of GO was synthesized by a modified Hummers method. Morphology of the composite particles was studied by both scanning electron microscopy and transmission electron microscopy, while their structure and chemical components were examined via X-ray diffraction and Fourier-transform infrared spectroscopy, respectively. All the data confirmed the coexistence of PS and GO with the expected core-shell structure of the composite. In addition, for the study on the electroresponsive behavior, the composite was dispersed in silicone oil and its electrorheological (ER) characteristics were examined via both an optical microscope and a rotational rheometer which was equipped with a high voltage source. Without an electric field, it behaved like a fluid, however, when an external electric field is present, the particles became polarized and demonstrated typical chain-like ER structures.