A Highly Stable, New Electrochromic Polymer: Poly(1,4-bis(2-(3′,4′-ethylenedioxy)thienyl)-2-methoxy-5-2″-ethylhexyloxybenzene)

A highly stable new electrochromic polymer, poly(l,4-bis(2-(3′,4′-ethylenedioxy)thienyl)-2-methoxy-5-2″-ethylhexyloxybenzene) (P(BEDOT-MEHB)) was synthesized and its electrochemical and electrochromic properties are reported. P(BEDOT- MEHB) showed a very well defined electrochemistry with a relatively low oxidation potential of the monomer at + 0.44 V versus Ag/Ag⁺, E_1/2 at -0.35 V versus Ag/Ag⁺ and stability to long-term switching up to 5000 cycles. A high level of stability to over-oxidation has also been observed as this material shows limited degradation of its electroactivity at potentials 1.4 V above its half-wave potential. Spectroelectrochemistry showed that the absorbance of the π-π* transition in the neutral state is blue-shifted compared to PEDOT, displaying a maximum at 538 nm (onset at 640 nm), thus giving an almost colorless, highly transparent oxidized polymer with a bandgap of 1.95 eV. Different colors observed at different oxidation levels and strong absorption in the near-IR make this polymer a good candidate for several applications.