Free-standing oligo(oxyethylene)-functionalized polythiophene with the 3,4-ethylenedioxythiophene building block: electrosynthesis, electrochromic and thermoelectric properties

Abstract A free-standing ordered polymer of P(EDT-E5-EDT) based on oligo(oxyethylene)-functionalized polythiophene with two 3,4-ethylenedioxythiophene units as building blocks was electrosynthesized successfully at a low oxidation potential, and comparatively investigated in three electrolytes of ACN/LiClO 4 , PC/LiClO 4 and ionic liquid BmimPF 6 . Interestingly, one ordered film obtained from PC/LiClO 4 resulted in its electrical conductivity up to 40 S m −1 depending on the mild growth condition. Among the fabricated P(EDT-E5-EDT) system, electronic transport is an important factor to receive a highest Seebeck coefficient of 35.9 μV K −1 . P(EDT-E5-EDT) films also exhibited favorable electroactivity and remarkable redox stability in especial. Moreover, the resultant films were demonstrated the electrochromic nature by color changing from salmon pink to blue, and broad absorption can be observed in near infrared region with the band gaps of 1.88–1.93 eV. Further switching transmittance revealed that polymers had reasonable contrast ratios (17.35–52.36%), high coloration efficiencies (151.6–363.5 cm 2 C −1 ), excellent switching stability and color persistence. The effective EDOT moieties in the chain plays a great role in the advanced properties, which could be developed to be semiconducting polymers in many electronic application areas.