Donor–acceptor type neutral green polymers containing 2,3-di(5-methylfuran-2-yl) quinoxaline acceptor and different thiophene donors

• Three novel donor-acceptor type polymers are synthesized and characterized.
• Two polymers are shown to be neutral-state green polymeric materials with high optical contrasts.
• Three polymers are shown paramount choices for the polymer electrochromic display applications.

A series of donor–acceptor type π-conjugated monomers containing quinoxaline moiety in the backbone as the acceptor unit and thiophene derivatives as the donor unit have been synthesized by Stille coupling. The effects of different donor substituents on the polymer’ electrochemical and spectroelectrochemical properties were examined. 2,3-di(5-methylfuran-2-yl)-5,8-bis(2-(3,4-ethylenedioxythiophene)) quinoxaline (MFEQ) with strong electron-donating ethylenedioxy group has a lower oxidation potential than that of 2,3-di(5-methylfuran-2-yl)-5,8-bis(2-thienyl) quinoxaline (MFTQ) and 2,3-di(5-methylfuran-2-yl)-5,8-bis(2-(3-methoxythiophene)) quinoxaline (MFMQ). The optical properties of polymers are also tuned due to different strength of donor units. Both PMFEQ and PMFMQ exhibit a green color in the neutral state, while PMFTQ with two absorption bands at 360 nm and 558 nm is purple. As donor–acceptor type materials, all three polymers can be both p- and n-doped, with fast response time, narrow band gap and high optical contrast (ΔT%).

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