Copolyaniline/Polystyrene Core-Shell Structured Microspheres and Their Electrorheology

초록

The electric field-responsive colloidal suspension, known as an electrorheological (ER) fluid, is one of the smart and intelligent fluid systems with an ability to transform from a liquid-like to a solid-like state by the stimulation of an external electric field [1-2]. Among the many promising materials for ER suspensions, conducting polymers in a semiconducting regime including polyaniline [3] and its derivatives [4], have been adopted as anhydrous dry-base ER fluids because of their ease in handling and superior physical properties, compared to various hydrous wet-base ER materials. Core-shell structured ER particles containing these materials as either core or shell species have attracted increasing interest owing to their outstanding advantages of an enhanced ER effect or diverse ER mechanism, lighter particulate density and lower cost. In this study, we synthesized core/shell structured semiconducting polystyrene/poly(2-methylaniline) (PS/PMAN) microspheres via a controlled swelling-releasing process in which the pre-dispersion polymerized PS seeds are adopted. To confirm a successful synthesis, we observed by scanning electron microscope, transmission electron microscope (Fig 1.), Fourier transform infrared and thermogravimetry analysis. ER behavior of PS/PMAN based ER fluid was measured by a rotational rheometer with a DC high voltage generator and analyzed with our suggested flow curve model, Cho-Choi-Jhon (CCJ) model [5]. Fig. 2 represents the flow curves (shear stress vs. shear rate) of the ER fluid indicating the significant increase in shear stress when an external electric field is applied. The shear stresses are enhanced with increasing of electric field strength and become stable in the whole shear rate range as the electric field reaches 4.0 kV/mm.