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As a novel candidate of electrorheological (ER) material, core/shell composite particles (PAPMMA) of poly(methyl methacrylate) (PMMA) core and polyaniline (PANI) shell were prepared and adopted as a dispersed phase. PAPMMA particles, obtained by a dispersion polymerization method, were spherical and possessed a monodisperse particle size distribution, in which the PANI shell was introduced on the surface of PMMA via an in-situ polymerization of aniline by adding an oxidant in an aqueous acidic solution. Yield stress of the PAPMMA suspensions under an applied electric field was observed to be increased with a particle size. In addition, monodisperse acrylic microspheres with aniline moiety on the surface were prepared by a seeded emulsion method, and then composite particles possessing chemically bonded PANI shell (PA-PGMA) were prepared via an in-situ polymerization of aniline. Their ER characteristics were also examined. [ABSTRACT FROM AUTHOR]

We report our experimental results on the electrorheological (ER) characteristics of ER fluids consisting of suspensions of semiconducting polyaniline and copolyaniline particles in silicone oil. Ionic sodium diphenylamine sulfonate and nonionic o-ethoxyaniline were introduced to synthesize copolyanilines, i.e. N-substituted copolyaniline and poly (aniline-co-o-ethoxyaniline), respectively. ER fluids using these particles were compared. ER fluids, which contain the ionic copolymer, showed the highest ER performance among polyaniline and its copolymer systems. This result was interpreted in terms of the conductivities of the particles and their dielectric spectra. [ABSTRACT FROM AUTHOR]