Synthesis and spectroelectrochemical characterization of multi-colored novel poly(3,6-dithienylcarbazole) derivatives containing azobenzene and coumarin chromophore units

Azobenzene and coumarin units bearing four novel 3,6-linked thiophene-carbazole-thiophene type electroactive monomers were synthesized in order to observe the effects of strong chromophore units on the electrochemical and spectroelectrochemical behaviors of resulting pi-conjugated conducting polymers (PTCbzAz, PECbzAz, PTCbzCo and PECbzCo). Electronic and optoelectronic properties of all polymers were investigated by cyclic voltammetry and in situ spectroelectrochemical studies, and their oxidation potentials, HOMO/LUMO energy levels, band gaps (E-g(op)), optical contrasts (Delta T%) and switching times were reported in detail. It was observed that incorporation of strong chromophore units in polymer backbones resulted in poly(3,6-dithienylcarbazole) derivatives with different optical band gap values and different number of colored states. The optical band gap values for PECbzAz, PECbzCo, PTCbzAz, PTCbzCo and were calculated as 1.71 eV, 1.75 eV, 1.93 eV and 2.07 eV, respectively, from the onset of pi-pi* transition in polymer films' neutral state absorptions. All polymers exhibited multicolored electrochromic behavior upon extarnally applied potential. Reported electrochemical and optical features of PECbzAz, PECbzCo, PTCbzAz, PTCbzCo suggest that these poly(3,6-dithienylcarbazole) derivatives are promising candidates for multicolored electrochromic device applications. (C) 2016 Elsevier Ltd. All rights reserved.