Electrochromic and spectroelectrochemical properties of polythiophene β-substituted with alkyl and alkoxy groups
Polythiophenes are conjugated polymers that are highly promising candidates for use as an active layer in flexible optoelectronic devices. The β-substitution position in the thiophene ring minimizes the occurrence of couplings during polymerization, producing more regular structures and resulting in better properties. The relatively high stability and the possibility of tuning the properties by molecular engineering make polythiophenes one of the most versatile classes of conjugated polymers. In this study, we present an investigation of the influence of two types of polythiophenes on their spectroelectrochemical properties: (i) poly(alcoxythiophenes) (POTs), including poly(3-methoxythiophene) (PMOT) and poly(3,4-ethylenedioxythiophene) (PEDOT), and (ii) poly(3-alkylthiophenes) (PYTs), including poly(3-hexylthiophene) (P3HT) and poly(3-dodecylthiophene) (PDDT). The polymers were electrochemically synthesized by cyclic voltammetry and characterized by infrared spectroscopy. The “in situ” simultaneous optical absorption and fluorescence investigation of the solutions showed new energy state polarons in the redox process. Chronoabsorptometry measurements enabled determination of parameters such as electrochromic efficiency, coulombic efficiency, optical contrast, and switching time of the polymers in the reduced and oxidized states. A switching time of 2 s and an electrochemical efficiency of almost 90 cm2 C−1 are promising for applying these polymers in electrochromic devices.
KeywordsSubstituted polythiophenes Electrochemistry Electrochromism
This work was supported by CNPq (457586/2014-1), CAPES, FAPEMIG (TEC-APQ-02715-14), and CTNano. We also would like to thank professors Tulio Matencio - UFMG and Marcos Roberto de Abreu Alves - UNIFEI for the important discussions.
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