ELECTROCHEMICAL CHARACTERIZATION OF A THERMORESPONSIVE N-ISOPROPYLACRYLAMIDE-VINYLFERROCENE COPOLYMER FILM BY THE USE OF QUARTZ-CRYSTAL OSCILLATORS

N-Isopropylacrylamide was copolymerized with vinylferrocene (13:1), and an electrode was coated with a film of thus obtained copolymer. Electrochemical and other properties of the film were examined at various temperatures by use of quartz crystal oscillators coupled with conventional electrochemical measurement systems. The copolymer film showed thermally induced volumetric phase transition; at higher or lower temperatures than the transition temperature (T(t)), the film is shrunken or swollen, respectively, in aqueous media. The apparent diffusion coefficient for the homogeneous charge transport in the swollen film is at least 5-fold larger than that in the shrunken film. The apparent formal potential of the film is also different between the swollen and shrunken states. Further, the phase transition temperature for the oxidized film was found to be higher than that for the reduced film. Thus, it was found that the copolymer film has two functions, namely, conversion of thermal information into electrochemical one and electrochemical control of phase transition or the transition temperature.