The Polymerization and Oxidation of Pyrrole by Halogens in Organic Solvents

Abstract

Simultaneous chemical polymerization and oxidation of pyrrole have been initiated by a halogenic electron acceptor, bromine or iodine, in various organic solvents. The polypyrrole (PPY)-halogen charge transfer (CT) complexes obtained from polymerization in acetonitrile are of particular interest. Both the PPY-I₂ and PPY-Br₂ CT complexes are granular in nature and have an electrical conductivity in the order of 1 to 10 ohm⁻¹ cm⁻¹. Both complexes show remarkable stability in the atmosphere and in the presence of moisture. The PPY-I₂ and PPY-Br₂ CT complexes in the form of thin, coarse films have also been synthesized on a SnO₂ electrode by electrochemical polymerization in acetonitrile. The physicochemical properties of the PPY-I₂ and PPY-Br₂ CT complexes prepared by the chemical methods are characterized by means of UV-visible and IR absorption spectroscopy, thermal and chemical analysis, and electrical conductivity and density measurements.