The electrochemical behavior and electron spin resonance response of thin films of tetracyanoquinodimethane polyester in contact with aqueous buffers have been studied. The results indicate that the coupling of electron- and proton-transfer steps in the classical 3 ⨯ 3 square scheme, which describes quinone electrochemistry, can significantly influence the charge-transport rate through the film, limiting the electroactivity to a fraction of the available electron-transfer sites and decreasing the effective diffusion coefficient for charge transport through the polymer film by 100-fold for specific conditions. The acid-base chemistry of the reduced acceptor sites in the film matrix accounts for the pH dependence of the voltammetric waves, the film passivation in acidic solutions, and the film dissolution at negative potentials in simple salt electrolytes. The acid dissociation constants of the reduced acceptor sites in the polymer matrix are estimated from the pH dependence of the E1/2values-for TCNQH2pKavalues of 6.9 ± 0.1 and 10 are obtained in aqueous phosphate buffers.
ASJC Scopus subject areas
- Colloid and Surface Chemistry