Polyaniline and its modification for electroresponsive material under applied electric fields

Polyaniline (PANI) and its various copolymers were synthesized using different monomers such as o-methyl-, o-methoxy-, o-ethyl-, o-ethoxyaniline and sodium diphenylamine sulfonate by the chemical oxidation polymerization as air-stable organic conducting polymers, and adopted as one of the most potential materials of electrorheological (ER) fluids, especially for the anhydrous system. A relatively low density, a controllable conductivity, and thermal stability are advantages of the PANI based ER system compared with other ER materials. An FT-IR analysis was adopted to confirm their synthesis and a scanning electron microscopy (SEM) analysis indicated the shape of PANI derivatives was irregular. The effect of functional group of PANI on electric and electroresponsive properties of poly(aniline-co-ethoxyaniline) (COPA) particles were examined. A universal scaling equation of the yield stress was applied to these ER fluids and it was found that all data were collapsed successfully onto a single curve regardless of monomer type of the polyaniline synthesized. Copyright # 2005 John Wiley & Sons, Ltd.