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Current Applied Physics 7 (2007) 352–355 /locate/cap www.kps.or.kr Carbon nanotube/polyaniline nanocomposites and their electrorheological characteristics under an applied electric ?eld C.S. Choi, S.J. Park, H.J. Choi * Department of Polymer Science and Engineering, Inha University, Incheon 402-751, Republic of Korea Received 10 May 2006; accepted 14 September 2006 Available online 30 October 2006 Abstract A conducting polyaniline (PANI) was synthesized via an oxidative dispersion polymerization technique, using poly(vinyl alcohol) (PVA) as a polymeric stabilizer, in the presence of multi-walled carbon nanotubes (MWNT) puri?ed in acidic solution, and dispersion stability of the MWNT in an aqueous solution of PVA was studied for di?erent PVA concentrations. Their morphology was con?rmed by a scanning electron microscope. Its electrorheological (ER) characteristics were also investigated by dispersing the PANI/MWNT composite particles in an insulating silicone oil. Its ER properties were examined using a rotational rheometer under varying applied DC electric ?eld strengths, in which the ER ?uid is generally composed of a suspension of conducting particles dispersed in an insulating ?uid, which shows a rapid and reversible change in shear viscosity with an applied electric ?eld. Synthesized PANI/MWNT composite particles are observed to enhance interparticular interactions, since the degree of polarization of PANI/MWNT composite particle increases with applied electric ?eld strengths. The shear stresses of the PANI/MWNT nanocomposite based ER ?uid increase with the electric ?eld strength for a broad range of shear rates. ó 2006 Elsevier B.V. All rights reserved. PACS: 73.61.Ph; 47.65.Gx; 83.80.Gv; 83.80.Hj Keywords: Carbon nanotube; Polyaniline; Dispersion; Electrorheological ?uid 1. Introduction Carbon nanotubes (CNTs)/polymer nanocomposites have been widely applied for various industrial applications due to their interesting characteristics of good thermal property, s