Core-shell structured conducting polyaniline (PANI)-coated polystyrene (PS) composite nanospherical particles were synthesized and assessed as a candidate for electrorheological (ER) materials. Mono disperse PS nanospheres were initially synthesized by a dispersion polymerization process and their surface was modified using concentrated sulfuric acid. This allowed the aniline monomer to be adsorbed easily on the sulfonated PS nanosphere and polymerized further by forming a PS/PANI nanosphere. The ER performance of their suspension dispersed in silicone oil was examined using a rotational rheometer under a variety of electric field strengths. The Bingham fluid model was used to analyze their flow curves to understand the interrelation between shear stress and shear rate. The relationship between the yield stress and electric field strength showed a slope of 2.0 following a polarization model. The dielectric spectra showed a good correlation with the ER performance of the ER fluid. (C) 2017 Elsevier Ltd. All rights reserved.