HIGH-CONTRAST ELECTROCHROMIC POLYMERS FROM ALKYL-DERIVATIZED POLY(3,4-ETHYLENEDIOXYTHIOPHENES)

The syntheses of two new derivatives of 3,4-ethylenedioxythiophene (ED OT), specifically 5-octyldioxeno[2,3-c]thiophene (EDOT-C-8) (2) and 5- tetradecyldioxeno[2,3-c]thiophene (EDOT-C-14) (3), and their polymers are reported in this paper. Cyclic voltammetry of 2 and 3 in 0.1 M TBA P/CH3CN show irreversible monomer oxidation peaks (E-p,E-m) at 0.89 an d 0.93 V, respectively. Multiple scans yield electroactive and conduct ing polymer films on electrode surfaces. The PEDOT-C-8 and PEDOT-C-14 formed oxidize with relatively low peak potentials at -0.22 and -0.19 V, respectively, indicating the doped form of tile polymer to be quite stable. Both PEDOT-C-8 and PEDOT-C-14 show two reduction processes wi th peaks at -0.18 and -0.16 V (E-c2,E-p) and -0.55 and -0.36 V (E-c1,E -p) respectively. Optoelectrochemical studies reveal an E-g of 1.75 eV for both polymers. The polymers are electrochromic, relatively transm issive and light gray in the oxidized form, while being opaque and dee p purple in the reduced form exhibiting high electrochromic contrasts. Long term switching studies carried out in 0.1 M LiClO4/PC with Li/Li + as a reversible counter electrode shows that PEDOT, PEDOT-C-8, and P EDOT-C-14 retained 65%, 50%, and 62% of their electroactivity after 60 00, 9000, and 16 000 double switches, respectively.