EQCM Investigations of a Thin Polymer Film

This Application Note is intended to provide the reader with a general framework for characterization of an electroactive polymer film. Electropolymerization is a convenient way to control film growth either through repeated cycling, potential steps, or current steps. Examination of the film redox behavior in monomer-free, fresh electrolyte provides insight on doping and dedoping of these polymer films. Polybithiophene films were assembled by cycling an Au-coated 10 MHz quartz crystal between 0 and 1.5 V in the presence of 1 mM bithiophene solution containing 100 mM tetrabutylammonium perchlorate (TBAP) in acetonitrile (MeCN). Potentials are reported against a Ag/Ag+ pseudo-reference electrode. The Teflon? cell was outfitted with a Teflon o-ring to prevent swelling from the acetonitrile and placed inside a VistaShield?. The cell was connected to an eQCM 10M? which was coupled to a Reference 600?. Both instruments were connected to a computer running Resonator? version 5.67. Bithiophene, electropolymerizes via a two-electron oxidation at potentials greater than ~1.25 V versus a Ag/Ag+ pseudo reference electrode.