Transport of neutral species in electroactive polymer films

A new procedure has been applied to the analysis of electrochemical quartz crystal microbalance data for transfer of mobile species in electroactive polymer films. The procedure enables the distinction between global equilibrium and rate-limiting transfer of electrons, ions and neutral species during film redox conversion. For polyvinylferrocene, polythionine and polybithiophene films (under the experimental conditions employed), transfer of a neutral species was found to be rate limiting. In the first two cases, solvent (water) was unequivocally identified as the slow species. In the third case, solvent (CH₃CN) transfer was tentatively identified as the rate-limiting step. Slow transfer of neutral species is due to the absence of migration effects, which can aid ion transfer. Transfer rates depend on direction of transfer in all three systems.