Synthesis and optical and electrochemical properties of novel copolymers containing alternating 2,3-divinylquinoxaline and hole-transporting units

For the enhancement of charge affinity, electron-affinitive 2,3-divinylquinoxaline and a series of hole-transporting chromophores (iminodibenzyl, phenothiazine, dihexyloxybenzene, and didodecyloxydistyrylbenzene) were incorporated alternately into the polymeric main chain. The resulting copolymers (P1-P4) were basically amorphous materials and were thermally stable below 300°C. The electronic structures, photoluminescence, and electrochemical properties of these copolymers were mainly determined by the electron-donating chromophores in the backbone. They showed significant positive solvatochromism in formic acid. An electrochemical study revealed that they exhibited lower band gaps (<2.3 eV) due to alternating donor and acceptor conjugated units (push-pull structure). Single-layer light-emitting diodes of aluminum, P1-P4, and indium tin oxide glass were fabricated, and preliminary electroluminescence spectra showed that P1, P3, and P4 were orange-emitting materials.