Abstract
Four donor–acceptor type conducting polymers, namely poly(2,3-bis(4-decyloxy)phenyl)-5,8-bis(4-thiophen-2-yl)pyrido[4,3-b]pyrazine) (P1), poly(2,3-bis(4-decyloxy)phenyl)-5,8-bis(4-butylthiophen-2-yl)pyrido[4,3-b]pyrazine) (P2), poly(2,3-bis(4-(decyloxy)phenyl)-5,8-bis(4-hexyloxythiophen-2-yl)pyrido[4,3-b]pyrazine) (P3) and poly(2,3-bis(4-(decyloxy)phenyl)-5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)pyrido[4,3-b]pyrazine) (P4), containing thiophene or its derivative as the donor and pyrido[4,3-b]pyrazine as the acceptor were prepared and characterized by cyclic voltammetry, scanning electron microscopy, and UV-Vis spectroscopy to detect the influence of the donor units’ strength on the electrochromic performances. The results demonstrated that all of the polymers could be reversibly reduced and oxidized by p-type doping and n-type doping, and showed near-infrared activities and different color changes in p-type doping process. Especially, P3 and P4 showed lower optical band gap than P1 and P2 due to the strong electron-donating hexyloxythiophen group of P3 and ethylenedioxythiophene group of P4. Besides, P3 and P4 displayed the saturated green color at the neutral state and the desirable transparency at the oxidized state. All the polymers displayed desirable optical contrasts, satisfactory coloration efficiency, excellent stability and short switching time, which made the polymers fascinating candidates in the electrochromic device applications.
Highlights
Electrochromism is defined as the reversible optical change phenomenon during the electrochemically redox process [1,2]
TheElectrochemistry four polymers were produced on the working electrode through cyclic voltammetry (CV)
The four polymers were produced on the working electrode through cyclic voltammetry (CV)
Summary
Electrochromism is defined as the reversible optical change phenomenon during the electrochemically redox process [1,2]. Among the various NIR electrochromic materials, we focus on donor–acceptor (D-A) type conjugated polymers because of their low band-gap, which can lead to a spectral shift to the long wavelength into the NIR region [3,11]. D-A type polymers, which consist of alternate electron-donating and electron-withdrawing moieties, have the intra- and/or inter-molecular charge transfer (CT) bands arising from push/pull interactions between the D and A units. Polymers 2016, 8, 377 transfer (CT) bands arising from push/pull interactions between the D and A units. When the donor and acceptor match appropriately, hybridization of the electronic levels of highest occupied appropriately, hybridization the electronic levels of highest occupiedorbital molecular orbital leads (HOMO)
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