Electrochromic polymer based on a rigid cyanobiphenyl substituted 3,4-ethylenedioxythiophene

A cyanobiphenyl substituted 3,4-ethylenedioxythiophene (EDOT) derivative was synthesized in order to test the hypothesis that a bulkier substituent leads to better contrast in electrochromic polymers based on alkylenedioxythiophenes. Electropolymerization of this derivative resulted in the formation of a highly electroactive and well-adhered polymeric film on the electrode surface. Spectroelectrochemical studies indicated that the polymer switches from a highly transmissive state in the oxidized form to an opaque dark-blue in the reduced state. Optical switching studies showed that the polymer films could be fully switched between its reduced and oxidized form in ca. 0.4-1.0 s with a DeltaT% of 67%. In situ conductivity studies showed a sharp transition from insulating state to the conducting state at around -0.5 V with maximum in situ conductivity of 0.03 S/cm. (C) 2001 Elsevier Science B.V. All rights reserved.