The thermodynamics of thin films (< 200 nm) of plasma-polymerized vinylferrocene (PPVF) deposited on various substrates have been examined in aqueous and non-aqueous electrolytes by controlled potential coulometry. The Nerst plots (E vs log[cFc+/cFc0]) of these data give slopes in the range of 120-150 mV/decade. Scanning electron microscopy of thicker films (> 400 nm) shows that significant physical damage can occur during electrolysis. These and related observations suggest that the super-Nersntian behavior may be related to stress induced by the forced incorporation of the anion of the supporting electrolyte, as is required to maintain electroneutrality within the films. A mechanical/electrochemical model is employed to explain the origin of the excess free energy required to convert ferrocene sites to ferrocenium sites within the PPVF films.