A Study on Formation of Needle-like Polyanilines
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A Study on Formation of Needle-Like Polyanilines Woo-Hyuk Jung1, Dong-Young Kim2, Young-Moo Lee3, and Stephen P. McCarthy1 1 Plastics Engineering, University of Massachusetts Lowell, One Univerisity Ave., Lowell, MA, 01854 2 Photoelectronic Materials Research Center, Korea Instutue of Science and Technology, 39-1 Hawelgok-dong Sungbuk-gu, Seoul, 136-791, Korea, Republic of 3 Industrial Chemistry, Hanyang University, 17 Haengdang-dong Sungdong-gu, Seoul, 133-791, Korea, Republic of ABSTRACT Needle-like polyanilines (PANi) were prepared at 15 oC by emulsion polymerization and their conductivities were obtained up to 3 S/cm according to the addition rate of ammonium peroxysulfate (APS) aqueous solutions with reaction conditions of 0.4 to 0.5 APS/aniline ratios and 0.4 to 0.5 M aniline concentrations. Needle-like complexes doped with p-toluenesulfonic acid (pTSA) were prepared with the oxidant solution added so slowly as to be for 3 to 3.6 hours. The high reaction temperatures ranging from 5 to 15 oC was the second condition to have needlelike anilinium complexes polymerized without their breaking during polymerization. A filler shape is one of the most important parameters influencing a percolation concentration of conductive fillers dispersed in a non-conductive matrix. Needle-like polyanilines could be potentially used as conductive fillers to show electromagnetic interference and radar absorption effects. INTRODUCTION Polyanilines in situ doped by aromatic sulfonic acids have become attractive materials to polymer researchers for several decades, and a huge number of publication on the subject of polyanilines have been put out. Aniline is a cheap product whose polymerization is straightforward, and polyanilines are very stable materials even showing high conductivity. Their yields increased getting along the amounts of oxidants added. Moreover, a conductive form of polyanilines showed excellent chemical stability, combined with relatively high levels of electrical conductivity [1-2], and thermal stability [3]. Intrinsic conducting polymers have the unique properties such as the capability to transfer charges into intrachains, interchains and interparticles [4], the controllable electrical properties by doping and dedoping [5], and good thermal stability to electrical, electrochemical and optical properties [6]. Conducting polymers might actually replace many heavy metal parts due to the good electrical bulk conductivity on doping for the fields of secondary battery [7-8], media for erasable information storage [9], electromagnetic shielding and artificial muscles, and could reach new applications to electronic polymer fibers, media of polymer dispersed liquid crystal displays, light electroluminescence devices, non-linear optics, membranes for selective gas separation, catalysts, and biosensors. The mixture of conductive and insulating materials offers good feasibility of electromagnetic shielding materials. In general, the conductivity of such a mixture increased drastically at a certain concentration
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