Electrosynthesis and characterization of a multielectrochromic copolymer of 1,4-bis(2-thienyl)-naphthalene with 2,2′-bithiophene

Abstract Electrochemical copolymerization of 1,4-bis(2-thienyl)-naphthalene (BTN) and 2,2′-bithiophene (BT) is carried out in acetonitrile (ACN) containing sodium perchlorate (NaClO4) as a supporting electrolyte. Cyclic voltammetry (CV), UV–vis and FT-IR analyzes confirm that the resulting polymer is a copolymer rather than a blend or a composite of the respective homopolymers. The obtained P(BTN-co-BT) film exhibits five different colors (orange yellow, yellowish green, green, greenish blue and blue) under various potentials, revealing distinct electrochromic properties from that of the BTN homopolymer film. Maximum contrast (ΔT%) and response time of the copolymer film are measured as 32.7% and 0.59 s at 750 nm. Electrochromic device (ECD) based on P(BTN-co-BT) and poly(3,4-ethylenedioxythiophene) (PEDOT) is also constructed and characterized. This ECD shows a maximum optical contrast (ΔT%) of 24.2% in visible region with a response time of 0.32 s at 780 nm. The coloration efficiency (CE) of the device is calculated to be 308 cm2 C−1 at 780 nm.