Electrochemical and spectroelectrochemical studies of poly(2,5-di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-ylthienyl) derivatives bearing azobenzene, coumarine and fluorescein dyes: Effect of chromophore groups on electrochromic properties

Three novel thiophene based monomers, 2,5-di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-ylthienyl derivatives, 1-{4-[(2,5-Di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl-3-thienyl) methoxy] phenyl}-2-phenyldiazene) (ETEAz), 4-[(2,5-Di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl-3-thienyl) methoxy]2H- chromen-2-one) (ETECo) and methyl 2-{6-[(2,5-Di-2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl-3-thienyl) methoxy]-3-oxo-3H-xanthen -9-yl} benzoate (ETEFlo), were synthesized and their conducting polymers were electrochemically prepared on ITO glass electrodes for the first time. The electroactive monomers were functionalized with strong chromophore groups such as azobenzene, coumarine and fluorescein in order to investigate the effect of chromophore units on electrochemical and spectroelectrochemical characteristics of corresponding conducting polymers. Spectroelectrochemical studies demonstrated that combination of a strong chromophore group with polymer backbone leads to significant changes in electronic and optoelectronic behaviors of resulting conducting polymers. PETEAz, PETECo and PETEFlo exhibited multicolored electrochromism with three distinct states. PETEAz revealed 33% (565 nm) and 52% (1270 nm) transmittance changes (Delta T%), while PETECo exhibited 40% (535 nm) and 64% (1245 nm) at their dominant wavelenghts. The optical contrasts of PETEFlo were measured as 15% (495 nm), 28% (560 nm) and 43% (1345 nm), which were lower than those of PETEAz and PETEFlo. It was observed that all conducting polymer films could be very quickly switched between their neutral and oxidized states in both visible and NIR regions. Switching times values were found to be 0.3 s at 565 nm and 0.4 s at 1270 nm for PETEAz, 0.4 s at 535 nm and 0.5 s at 1245 nm for PETECo, 0.4 s at 495 nm, 0.4 s at 560 nm and 0.7 s at 1345 nm. Moreover, the optical band gap values for PETEAz, PETECo and PETEFIo were calculated as 1.6 eV, 1.4 eV and 1.55 eV, respectively, from the onset of pi-pi* transition in polymer films' neutral states. a 2014 Elsevier Ltd. All rights reserved.