Electrochemical polymerization, characterization and in-situ conductivity studies of poly-3,4-ortho-xylendioxythiophene (PXDOT)

The electrochemical polymerization of 3,4-ortho-xylendioxythiophene (XDOT) in acetonitrile on Pt electrode let to obtain stable and well-adhered conducting polymer films. The voltamperometric response of the poly-3,4-ortho-xylendioxythiophene (PXDOT) showed a mirror-image, indicating fast electron transfer (ΔE_p = 60 mV), which is a rare phenomenon in thick layers of conducting polymers. The in-situ electrochemical conductance experiments showed that the maximal conductance for PXDOT is reached at lower potentials and with less hysteresis than the observed for PEDOT, confirming a fast electrochemical response of the polymer. This behavior could be attributed to the presence of the xylen-unit attached to the polymer chain, which generates an internal order on the oligomeric chains, forming channels that facilitate the mobility of the electrolyte ions during the charge/discharge processes. Additionally, PXDOT showed an irreversible cathodic process which does not correspond to an n-doping, nevertheless induce a polymer internal rearrangement, which causes a major change in the p-doping signal. This cathodic process thus, it was attributed to the reduction of intrachain charge-trapped that was produced during electropolymerization.