Formation and redox transformations of polyphenazine

Abstract

The electropolymerization of phenazine (Ph) in acidic aqueous media was studied on a gold electrode by cyclic quartz crystal microbalance measurements. It is demonstrated that polyphenazine films can be prepared by oxidative electropolymerization. The results of the electrochemical microgravimetry are consistent with a redox mechanism where H 3O + ions are inserted in the first reduction step and anions are expelled in the second reduction step in acid solutions. Simultaneously with the desorption of anions, a sorption of solvent molecules occurs. The latter is the slowest process, therefore the relative contributions of ions and solvent molecules to the mass change depend on the scan rate. The relative participation of these species is also related to the pH of the solution. At pH > 3 a transition from the reversible to irreversible behaviour and a decreasing electrochemical activity can be observed, as well as the anion exchange is replaced by cation exchange during the electrochemical transformations. The FTIR spectrum indicates that—in contrast with the poly(1-hydroxyphenazine) where the phenazine units are linked by ether bonds—the polymer is formed via C C or C N couplings.