Biomimetic Synthesis of Water Soluble Conductive Polypyrrole and Poly (3,4 ethylenedioxythiophene)
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Biomimetic Synthesis of Water Soluble Conductive Polypyrrole and Poly (3,4 ethylenedioxythiophene). Ferdinando F. Bruno, Jacqueline M. Fortier1, Ramaswamy Nagarajan1, Sucharita Roy1*, Jayant Kumar1, and Lynne A. Samuelson. Materials Science Team, Natick Soldier Center, U.S. Army Soldier and Biological, Chemical Command, Natick, MA 01760. 1 Departments of Physics and Chemistry, Center for Advanced Materials, University of Massachusetts Lowell, Lowell, MA 01854. *Presently at Organix Inc., Woburn, MA 01810 ABSTRACT A novel biomimetic method for the synthesis of a conducting molecular complex of polypyrrole and of Poly(3,4 ethylenedioxythiophene) (PEDOT) in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS) is presented. A poly(ethylene glycol) modified hematin (PEG-Hematin) was used to catalyze the polymerization of pyrrole and of 3,4 ethylenedioxythiophene in the presence of SPS to form a Polypyrrole/SPS and PEDOT/SPS complex. UV-vis, FTIR, electrical conductivity and TGA studies for all complexes indicate the presence of a thermally stable and electrically conductive form of these polymers. Furthermore the presence of SPS in this complex provides a unique combination of properties such as processability and water-solubility. Water-soluble polypyrrole opens new avenues for the fabrication of novel biosensors. INTRODUCTION The increasing environmental problem of hazardous chemical wastes, has led to an upsurge in efforts towards the development of biochemical alternatives for synthesis of electronic and photonic polymers. Enzymatic polymerization has attracted much attention using oxidative enzymes, such as horseradish peroxidase (HRP), for the synthesis of polyanilines and polyphenols through oxidative free radical coupling reactions.[1-3] The proposed mechanism for HRP catalyzed polymerization involves the interaction of the heme–iron cofactor of the enzyme with the peroxide yielding an oxidized heme-iron complex [4]. Subsequently the oxidized hemeiron complex reacts with the substrate in a one-electron transfer reaction to produce the substrate radical and a new iron-heme complex followed by the coupling of the radicals to form the polymer. However, until recently, this enzymatic approach could not be extended to other conducting polymers such as polythiophene or polypyrrole [5, 6]. This was due to the fact that monomers such 3,4-dimethoxythiophene (EDOT) and pyrrole (PYR) complexed with the active site of the enzyme catalyst, causing deactivation and thus proving to be unsuitable substrates for this enzymatic approach. This deactivation behavior drastically limited the prospects for the enzymatic synthesis of a wide range of polymers, such as poly (3,4-dimethoxythiophene) (PEDOT) and polypyrrole, which are desirable for such applications as antistatic thin films, organic lightweight batteries and smart display devices [6]. Encouraged by the numerous reports based on the use of Fe2+ catalysts, we investigated the use of biomimetic catalysts that could effectively simulate the action of
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