Synthesis and properties of photoluminescent polymers bearing electron-facilitating oxadiazole derivative side groups

Abstract

Poly(p-divinylene phenylene) derivatives bearing fluorene and carbazole units in the main chain and 5-phenyl-1,3,4-oxadiazole moieties as side groups were prepared by the polycondensation of a newly synthesized monomer, [2-(5'-phenyl-1',3',4'-oxadiazole-2'-yl)-1,4-xylylene]bis(triphenyl phosphonium bromide) (OXAD), with 9,9-dibutylfluorene-2,2'-dicarbaldehyde (DBFDA) and 9-(2-ethylhexyl)carbazole3,6-dicarbaldehyde (EHCDA), which gave DBFDA-OXAD and EHCDA-OXAD. Analogues of these polymers without the side groups were also synthesized by the reaction of 1,4-xylene bis(triphenyl phosphonium bromide) (PXYL) with the dicarbaldehydes, which gave DBFDA-PXYL and EHCDA-PXYL. All the synthesized polymers are soluble in organic solvents, giving films of good quality. The polymers are stable beyond 375 degreesC. They emit blue and blue-green light, and their quantum yields are 38-79% in solution and 1-24% in film, depending on the fluorene and carbazole units as well as the side groups. In particular, the OXAD-based polymers contain hole-facilitating backbones and electron-facilitating side groups, perhaps allowing these polymers to transport both holes and electrons. Overall, the synthesized polymers are potential candidates for the fabrication of light-emitting devices. (C) 2002 Wiley Periodicals, Inc.