Mechanical resonance effects in electroactive polycarbazole films

Abstract

Abstract We describe crystal impedance data acquired dynamically during the electropolymerization of carbazole, to produce polycarbazole films on the electrode surface. Data were obtained at the fundamental and third harmonic modes of a 10 MHz thickness shear mode resonator. At a critical thickness, the system exhibits mechanical resonance, a special condition in which the mechanical shear deformation across the polymer film corresponds to one quarter of the acoustic wavelength. This situation has not been reported previously for electroactive polymer films exposed to a liquid phase. At this point, the resonant frequency and admittance data show dramatic changes with polymer coverage. Prior to mechanical resonance, the impedance spectra can be fitted readily to a modified Butterworth–Van Dyke model, recognizing the presence of an ideal mass layer, a finite viscoelastic layer and a semi-infinite Newtonian fluid (the electrolyte). The data indicate spatial variation of shear modulus.