The synthesis of new donor–acceptor polymers containing the 2,3-di(2-furyl) quinoxaline moiety: Fast-switching, low-band-gap, p- and n-dopable, neutral green-colored materials

Abstract

Three donor–acceptor type π-conjugated polymers were synthesized electrochemically:poly[2,3-di(2-furyl)-5,8-bis(2-(3,4-ethylenedioxythiophene)) quinoxaline] (PFETQ), poly[2,3-di(2-furyl)-5,8-bis(2-thienyl) quinoxaline] (PFTQ) and poly[2,3-di(2-furyl)-5,8-bis(2-(3-methoxythiophene)) quinoxaline] (PFMTQ). All of the synthesized polymers, contained the 2,3-di(2-furyl) quinoxaline moiety in the backbone as the acceptor unit and different thiophene derivatives as the donor units. The electroactivity of the monomers and the electrochemical properties of their polymers were investigated by cyclic voltammetry. The presence of the strong electron-donating ethylenedioxy and methoxy groups on the aromatic structure increased the electron density. Thus, the oxidation potential of FETQ and FMTQ shifted to a lower value than that of FTQ. The optical properties of the polymers were investigated by UV–vis–NIR spectroscopy. Both PFETQ and PFMTQ reveal two distinct absorption bands in the red and blue regions of the visible spectrum, while PFTQ has only one dominant wavelength at 596nm in the visible region. The colorimetry analysis revealed that while PFTQ has a light blue color, PFETQ and PFMTQ are green in the neutral state. The optical band gaps, defined as the onset of the π–π* transition, were found to be 1.15eV for PFETQ, 1.2eV for PFMTQ and 1.34eV for PFTQ. Moreover, all three polymers showed both n-doping and fast switching times.