Synthesis and characterization of luminescent polyethers with 2,5-distyrylthiophene and aromatic oxadiazole chromophores

Two new luminescent copolyethers (P1 and P2) with isolated 2,5-distyrylthiophene-emitting segments and electron-transporting 2,5-diphenyl-1,3,4-oxadiazole chromophores were successfully synthesized by the Horner-Wadworth-Emmons reaction. The solubility, optical, and electrochemical properties of the polymers were investigated and correlated with nonlinear thiophene and 1,3,4-oxadiazole groups. P2 with pendant 1,3,4-oxadiazole was soluble in common organic solvents such as chloroform, tetrahydrofuran, and C₂H₂Cl₄. Thermogravimetric analysis and differential scanning calorimetry showed that the copolyethers were thermally stable below 345 °C, with glass-transition temperatures higher than 110 °C. They were yellow-greenish emitting materials with a band gap of 2.57-2.58 eV estimated from the onset absorption. Incorporating the thiophene moiety narrowed the band gaps of the copolyethers. The photophysical and electronic properties of the polymer and the preliminary electroluminescent device made from the polymer demonstrate that the polymer may be a potential candidate material for the fabrication of polymeric light-emitting devices.