Synthesis of polypyrrole–SBS composites and the particle size effect on the electrorheological properties of their suspensions

The electrorheological (ER) behavior of polypyrrole (PPy)–SBS composite suspensions was investigated. The PPy–SBS composites were prepared to improve mechanical and electrical properties, and thereby enhance the ER response of their suspensions. Various PPy–SBS composites were synthesized by emulsion polymerization controlling the amount of SBS. The ER response initially decreased and then increased with increasing amount of SBS. The dielectric constant and conductivity of the PPy–SBS composite particles and the dielectric constant of the PPy–SBS composite suspensions were not consistent with the ER behavior, but the particle size did. A power-law dependence, τ = 0.207βd2E3/2, shows a good fit to the ER behavior of PPy–SBS composite suspensions with various amounts of SBS. The dependence of E1.5 is consistent with the conduction model and the dependence of d2 is consistent with the polarization model, but the dependence of β is not consistent with the either model. A surfactant, Brij®30, was added to the PPy–SBS composite suspension to reduce the non-linear conduction and thereby enhance the ER response. It was observed that the ER response was enhanced by adding the surfactant.