In situ monitoring of viscoelastic/volume and mass changes occuring during the electrochemical growth and redox switching of poly(pyrrole) and poly(N-vinylcarbazole) films was performed using impedance analysis of quartz resonators. For that purpose, simultaneous measurements of damping resistance, charge, and frequency were carried out. The dopant anion (tetrafluoroborate, tosylate, dodecyl sulfate, and /8-cyclodextrintetradecasulfate) did not significantly affect the doping level of poly(pyrrole) layers lying between 0.21 and 0.34. However, by comparison with the other polymer matrix poly(N-vinylcarbazole), it is shown that, during growth, resistance changes depend greatly on the size and the amount of counteranions incorporated in the polymer matrix. Results are correlated to the film morphology. Volume or viscoelastic changes occurring upon redox switching only depend on the size and not the charge of counteranions. For small dopants, reversible changes of resistance are attributed to swelling/ shrinking. For large anions, the significant frequency upshifts observed upon reduction are attributed to an irreversible "softening" of the polymer network.Since their discovery about 10 years ago, conducting polymers have drawn the attention of the research community.1 They have found promising applications as light-weight rechargeable batteries, electrochromic displays,* 12 345and gas3-5 or muscle sensors6 78to cite a few. The mechanisms behind these applications are doping or undoping, charge compensation, and associated structural or volumetric changes. However, very little work has been devoted to the latter mechanisms.7•8 Indeed, the use of conducting polymers in the abovecited applications requires a firm knowledge of their morphology, adhesion properties, temperature stability, mechanical stability, etc. in the environment in which they operate.In the past few years, the electrochemical quartz crystal microbalance (EQCM) has been extensively used to study f Current address: CEA/DAM, Centre d'Études du Ripault, BP 16, F-37260 Monts, France.
