Electrosynthesis and characterization of a novel electrochromic copolymer of N-methylpyrrole with cyclopenta[2,1-b:3,4-b′]dithiophene

Electrochemical copolymerization of N -methylpyrrole (NMPy) and cyclopenta[2,1-b:3,4-b′]dithiophene (CPDT) was performed in acetonitrile containing sodium perchlorate as a supporting electrolyte. Characterization of the resultant copolymer P(CPDT-co-NMPy) was performed by cyclic voltammetry, UV–vis spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The P(CPDT-co-NMPy) film has distinct electrochromic properties and exhibits four different colors (reddish brown, pale khaki, pale sea green and light blue) under various potentials. The maximum contrast (Δ T %) and response time of the copolymer film at 750 nm were measured as 47.0% and 2.20 s, respectively. An electrochromic device (ECD) based on P(CPDT-co-NMPy) and poly(3,4-ethylenedioxythiophene) was constructed and characterized. The optical contrast (Δ T %) at 630 nm was found to be 40.2%, and the response time was measured as 1.77 s. The coloration efficiency of the device was calculated to be 476 cm 2 per C at 630 nm. The ECD also has satisfactory optical memories and redox stability.