Three ways to improve electrorheological properties of polyaniline-based suspensions

In order to improve further the electrorheological (ER) properties of polyaniline (PAn)-based suspensions, i.e., to enhance the static yield stress and to reduce the current density, three methods, namely, coating of the PAn particles with polymer, grafting on the particles with acrylamide, and nonequilibrium dedoping of the PAn particles with concentrated ammonia water, were tried. The results showed that PAn particles coated with poly(vinyl alcohol) or grafted with polyacrylamide can increase the static yield stress and decrease the current density of the ER suspension, whereas coating with poly (methyl methacrylate) or polystyrene reduced both the current density and the static yield stress. Nonequilibrium dedoping of the dried, protonated PAn particles with concentrated ammonia water showed the best effect on the ER properties of the suspension, exhibiting a static yield stress of 16 kPa with a current density of 2.7 mu A/cm(2) under a 2.8 kV/mm de electric field. (C) 1997 John Wiley & Sons, Inc.