Synthesis and electroluminescence properties of ortho-, meta- and para-linked polymers containing oxadiazole unit

A series of electroluminescent pi -conjugated polymers containing an oxadia zole group in the backbone was prepared through Heck's coupling or Wittig's condensation reaction, poly[(2,5-bis(5-hexyloxyphenyl)-1,3,4-oxadiazole)-2 ,2-diylvimylene-alt-1,4-phenyleneviny-lene] (POOXPV), poly[(2,5-bis(2-hexyl oxyphenyl)-1,3,4-oxadiazole)-5,5-divylvinylene-alt-1,4-phenylenevinylene] ( PMOXPV) and poly[(2,5-diphenyl-1,3,4-oxadiazole)-2,4-diylvinylene-alt-1,4-( 2,5-dihexyloxy)-phenylenevinylene] (PPOXPV). The three polymers were solubl e in common organic solvents and showed good thermal stability. The maximum photoluminescence (PL) wavelengths of POOXPV, PMOXPV and PPOXPV appeared a t 495, 470, and 510 nm, respectively. The electroluminescence (EL) spectra of POOXPV and PPOXPV showed maximum peaks at 500 and 510 nm, respectively, corresponding to greenish-blue light, with the single-layer light-emitting diodes of Al/polymer/ITO glass fabricated. In blending synthesized polymers with 4-(dicyanomethylene)-2-methyl-6-[p-(dimethylamino)stryl]-4H-pyran (DC M), polymers are also believed to serve as an excellent polymer electron-tr ansporting materials in our devices. (C) 2001 Published by Elsevier Science Ltd.