POLYPYRROLE-BASED ANION-EXCHANGE POLYMERS

The preparation and electrochemistry of two polypyrroles with cationic substituents in the 3-Position, and a precursor alkyl bromide substituted polymer, are reported. The electrochemical and ion-exchange properties of the new cationic polymers are similar to those of a previously reported N-substituted analogue. However, their lower redox potentials (ca. -0.1 V vs SSCE) mean that they become conductive at less oxidizing potentials. This is shown to be advantageous in the catalysis of ascorbate oxidation. The enhanced conductivity at low potentials also greatly accelerates the electrochemistry of electrostatically bound ferrocyanide. Surprisingly, the maximum conductivity of the new 3-substituted cationic polymers is lower than that of the N-substituted analogue. Poly[3-(3-bromopropyl)pyrrole] and cationic copolymers formed by its partial reaction with trimethylamine were used to probe the origin of this difference. Swelling of the polymers with electrolyte solution and associated morphological changes appear to be important factors.