A structural effect on electrochemical behavior of hetero-deposited redox polymer Langmuir-Blodgett films containing ferrocene and tris(bipyridine)ruthenium derivatives

A structural effect on the electrochemical behavior of hetero-deposited redox polymer Langmuir-Blodgett (LB) films containing ferrocene (Fc copolymer) and tris(bipyridine)ruthenium derivatives (Ru copolymer) on electrodes was investigated by cyclic voltammetry. The hetero-deposited LB film structure consists of Ru copolymer LB film (three layers) as an inner layer and Fc copolymer LB film (two layers) as an outer layer on ITO electrodes. The hetero-deposited redox polymer LB films which are prepared by the deposition at a surface pressure higher than 28 mN m(-1) show that the redox behavior of the ferrocene moiety in the outer Fc copolymer LB film is controlled by the redox condition of the ruthenium complex in the inner Ru copolymer LB film and not directly influenced by the electrode potential. On the other hand, in the LB films prepared at a pressure less than 25 mN m(-1), such behavior was not observed because the inner Ru copolymer LB films cannot work as an insulator between the outer Fc copolymer LB films and the ITO electrode. The voltammetric shapes of the Ru copolymer LB films were distorted with increasing deposition surface pressure. These results indicate that the insulating property of the inner layer is improved whereas the electron transfer rate in the interlayer becomes slower with increasing deposition surface pressure because of the formation of the high packing density of alkyl side chains of the LB films. (C) 1999 Elsevier Science S.A. All rights reserved.