Applications of the quartz crystal microbalance to electrochemistry. Measurement of ion and solvent populations in thin films of poly(vinylferrocene) as functions of redox state

The quartz crsytal microbalance (QCM) technique is applied to a study of ion and solvent content within poly(vinylferrocene) (PVF) as a function of redox state in various supporting electrolytes. It is concluded that in ClO₄^- and PF₆^- containing electrolytes the oxidation of the film occurs with little and no change in solvent content of the film, respectively. These findings are in agreement with previously postulated phaselike behavior for this system. Multiple peaks are observed in the voltammetry of the PVF film in Cl^- containing electrolytes. Based on the concurrent QCM measurements the structure in the voltammetric response is proposed to result from the electrochemically induced dissolution or delamination of the film and a new charge transport (diffusional) situation which results from loss of the film from the surface. The QCM technique is shown to be a powerful tool for the study of processes which result in mass changes at solid/liquid interfaces, especially electrode surfaces.