Effects of acceptor level on chemically synthesized polypyrrole-halogen complexes

Abstract

Electrically conductive polypyrrole (PPY)-halogen complexes have been synthesized by simultaneous chemical polymerization and oxidation of pyrrole. The ratio of pyrrole monomer to halogen (chlorine, bromine, or iodine) used in the synthesis was varied and the physicochemical and electrical properties of the resulting complexes were studied in detail. With all three halogens, the yield of the complex is affected by the initial amount of halogen used, with the properties of the polypyrrole-bromine complex showing the strongest dependence on the acceptor level. For this complex, both the percentage of bromine incorporated and the ratio of covalent to ionic bromide increase upon increasing the initial bromine concentration, while the electrical conductivity shows a maximum. Experimental evidence suggests that some halogen substitution at the pyrrole ring must have occurred in the PPY-Br2 and PPY-Cl2 complexes, but not in the PPY-I2 complex.