Electrorheological characteristics of poly(diphenylamine)/magnetite composite-based suspension

Electro-responsive poly(diphenylamine)(PDPA)/Fe₃O₄ composite particles were prepared by the synthesis of PDPA particles using a chemical oxidative polymerization technique followed by loading nano-sized Fe₃O₄ particles onto PDPA via a chemical co-precipitation process. The morphological image of the PDPA/Fe₃O₄ particles was characterized by scanning electron microscope and transmission electron microscope. The crystalline structure was scrutinized by X-ray diffraction. The rheological characteristics of the suspension composed of PDPA/Fe₃O₄ particles suspended in silicone oil were investigated by a rotation rheometer, demonstrating standard electrorheological (ER) characteristics with a dramatic increase in shear stress and dynamic moduli under the application of an electrical field strength. The shear stress curves under an electrical field could be described using the Bingham model and the yield stress showed a power-law relationship with the electric field strength with an exponent of 1.5, following the conduction model. Furthermore, the frequency-dependent dielectric behaviors of the PDPA/Fe₃O₄ ER suspension was tested using an inductance (L)-capacitance (C)-resistance (R) (LCR) meter. The dielectric properties were well described using the Cole-Cole equation and were consistent with the results of the ER experiments.