INSITU QUARTZ CRYSTAL MICROBALANCE RESPONSES AND ELECTROCHEMISTRY REGARDING LANGMUIR-BLODGETT-FILM OF VIOLOGEN POLYION COMPLEX ON THE ELECTRODE SURFACE

The electrochemical behavior and the response of the quartz crystal mi crobalance(QCM) for the Langmuir-Blodgett(LB) viologen film have been examined. LB monolayers employed are prepared by electrostatically fix ing the viologen monolayer containing the alkyl chain moiety on the po ly(potassium 1-sulfatoethylene). The number of monolayers accumulated on the polycrystalline Au electrode of a piezoelectric quartz crystal was controlled by changing the general vertical dipping times. The QCM frequency response for the first reduction scan of viologen dication (V2+) to monocation radical (V+.) shows extremely large frequency incr ease, qualitatively indicative of mass loss, viscoelasticity decrease, or mechanical stress decrease during the reduction. A frequency incre ase during the second reduction scan is also observed, although not as large as for the first scan. The frequencies increase continuously wi th increasing number of scans and the steady-state responses can only be obtained after many repetitive potential scans. The results of the conductance spectra measurements of the quartz crystal/LB film composi te resonator are interpreted as break-in and/or an increase of aggrega tion of the orientated structure during potential scans. The cyclic vo ltammetric wave obtained in the potential range 0 to -0.7 V vs. sodium chloride saturated calomel electrode has the characteristics of a sim ple, one electron transfer between V2, and V+., being chemically rever sible process. The subsequent cyclic voltammogram responses obtained a fter the first cycle of potential scan are nearly identical for some h ours, in contrast to the responses of the QCM. It is shown that struct ural change of the organized film dose not have a significant influenc e on the shape of the electrochemical response but does have an effect on the frequency response of the QCM.