Polarographic Studies on Aqueous Solutions of Poly-o-xylylviologen Dibromide

Abstract

Dropping mercury electrode polarography of the redox polymer poly-o-xylylviologen dibromide in water gave two well-defined irreversible diffusion controlled reduction waves over the pH range 1.70 to 6.40. The half-wave potentials for both waves (Wave I) = -0.404 V, E 1 /2 (Wave II)= -0.981 V vs SCE) are independent of pH and the total concentration of the solutions. However, the gross effect of pH on the relative wave heights suggests that an equilibrium of the type BH =+ H' + B (where B represents the compound studied) exists in solution where the reduction of the protonated as well as of unprotonated form of the polymer results in Waves I and 11, respectively. A tentative mechanism for the reduction processes is proposed. The dissociation constant of the protonated species was found to be 1.0 X 0.1 M) on calculation from a pH-dependence study of the limiting currents for both waves at a particular concentration. © 1985, Taylor & Francis Group, LLC. All rights reserved.