Luminescent copoly(aryl ether)s consisting of alternate oxadiazole and 1,4-distyrylbenzene derivatives: Synthesis and characterization

Abstract

In an effort to decrease the electron-injection barrier from the anode electrode, four copoly(aryl ether)s (P1–P4), consisting of alternating isolated electron-transporting [2,5-diphenyl-1,3,4-oxadiazole for P1 and P3 and 5,5′-diphenyl-2,2′-p-(2,5-bishexyloxyphenylene)-bis-1,3,4-oxadiazole for P2 and P4] and emitting chromophores (1,4-distyryl-2,5-dihexyloxybenzene for P1 and P2 and 1,4-distyryl-2,5-dihexylbenzene for P3 and P4), have been synthesized by the nucleophilic displacement reaction between bisfluoride and bisphenol monomers. They are basically amorphous materials with 5% weight-loss temperature above 400 °C. The photoluminescence spectra and quantum yields of these copolymers are dependent on the compositions of the two isolated fluorophores. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of these copolymers have been estimated from their cyclic voltammograms. All the observations directly prove that the oxidation starts at the hole-transporting segments. The electron affinity can be enhanced by the introduction of isolated electron-transporting segments that lead to a charge-injection balance. Single-layer light-emitting diodes (Al/P1–P4/ITO glass) have been fabricated. P1 and P2 reveal blue electroluminescence, and P3 and P4 reveal purple-blue electroluminescence. Moreover, the incorporation of bisoxadiazole units increases the electron affinity and reduces the turn-on electric field better than one oxadiazole unit. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2765–2777, 2003