Synthesis of a Multifunctional Quinoxaline and Benzodithiophene Bearing Polymer and Its Electrochromic Device Applications

Abstract

A quinoxaline (Qx) and benzodithiophene (BDT) comprising of random copolymers, namely poly(5-(6-(5-(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b ']dithiophen-2-yl)-4-(2-ethylhexyl)thiophen-2-yl)-4,8-bis ((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b ']dithiophen-2-yl)-2,3-bis(3,4-bis(octyloxy)phenyl)quinoxaline) (PQBT), is synthesized via Stille polycondensation reaction. To investigate the effect of the pi-bridge on the electrochromic properties, 3-(2-ethylhexyl) thiophene is incorporated the between Qx and BDT moiety. The resulting random copolymer is characterized by NMR spectroscopy, gel permeation chromatography (GPC), attenuated total reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM). PQBT exhibits ambipolar and multichromic characteristics and is highly soluble in common solvents. Optoelectronic studies reveal two well-separated absorption bands having maxima at 500 and 532 nm with 1.83 eV optical band gap (E-g(op)). PQBT exhibits orange color in the neutral state with brown, green, and blue colors in the intermediate, oxidized, and reduced states, respectively. Subsequently, a PQBT and poly-3,4-ethylenedioxythiophene (PEDOT)-bearing prototype bilayer electrochromic device working between orange and blue colors is constructed and characterized.