Electrochromic Linear and Star Branched Poly(3,4-ethylenedioxythiophene−didodecyloxybenzene) Polymers

Abstract

New linear and star structured poly(3,4-ethylenedioxythiophene−didodecyloxybenzenes) (PEBs) have been prepared which exhibit thermochromism and multicolor electrochromism as they are able to produce the three basic colors in the RGB system: red, green, and blue. The star polymer features a conjugated hyperbranched poly(triphenylamine) core with PEB arms ca. 8−10 repeat units (16−20 rings) in length. Red in solution, the optical spectra of both polymers exhibit a maximum absorption at 455 nm in the neutral state. Linear and star PEB are thermally stable up to 300 °C as demonstrated by TGA. The presence of an EDOT-phenylene repeat in the conjugated backbone results in a relatively low half-wave potential of +0.20 V vs Fc/Fc+, which is lower than regioregular poly(3-hexylthiophene) by 0.4 V and only slightly higher than PEDOT. As a result, star PEB is the first representative of a new class of star-shaped polymers where it is possible to address the electroactive arms independently from the conjugated core. The redox switching properties of these star PEBs are quite stable with a 90% retention of electroactivity after 4500 double potential switches. These properties are of particular importance for electrochemically based display applications where highly stable processable electrochromic polymers are needed.