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Electrochemical synthesis of polypyrrole in powder form
Novel approach to synthesis of conjugated oligomers/polymers is proposed. This approach combines all advantages of electrochemical methods: variation of the oxidation potential in wide range with high precision, direct control of the process rate and product yield, variation of both the doping anion/cation nature and the composition of polymerization medium, absence of chemical oxidative reagents in reaction mixture. Contrary to the conventional use of this synthetic method, it has been exploited in our study for generation of polymeric products outside the electrode surface. This goal has been implemented via oxidation of the monomer at porous electrode with simultaneous pumping of the polymerization medium (monomer in background electrolyte solution) through porous electrode with a certain rate. It leads to electrochemical generation of active intermediates (cation radicals) at the electrode surface with their recombination and subsequent accumulation of the products not only as film on the electrode surface but also as a colloid in solution outside the porous medium. Since this reaction path toward bulk solution products should evidently be favored by slow steps in the course of the polymer formation, this approach has been tested for pyrrole oxidation (both in its pure monomer solution and in the presence of the bromide redox mediator) since this monomer is known of its high rate of polymer chain formation.
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