Poly(p‐phenylene vinylene) derivatives containing triazole or oxadiazole segments: Connector effect in optical,electrochemical, and electroluminescent properties

To study the effect of connector structure between hole‐ and electron‐transporting segments, we synthesized and characterized new electroluminescent polymers P 1 – P 7 consisting of hole‐transporting 1,4‐bis(hexyloxy)‐2,5‐distyrylbenzene (DSB: P 1 and P 2 ) and electron‐transporting 4‐(4‐(hexyloxy)phenyl)‐3,5‐diphenyl‐4H‐1,2,4‐triazole (TAZ: P 3 and P 4 ) or 2‐(2,5‐bis(hexyloxy)‐4‐(5‐phenyl‐1,3,4‐oxadiazol)phenyl)‐5‐phenyl‐1,3,4‐oxadiazole (DIOXD: P 5 – P 7 ) segments linked by different connectors. The connectors between hole‐ and electron‐transporting segments are (1) 1,4‐phenylene in P 3 and P 5 , (2) 1,4‐divinylbenzene in P 4 and P 6 , and (3) 4,4′‐biphenyl in P 7 . Three corresponding end‐capped model polymers P 1‐M , P 2‐M , and P 3‐M were also synthesized to evaluate the effect of end groups. From optimized semiempirical MNDO calculations, the adjacent benzene rings between DSB and TAZ or DIOXD chromophores in P 3 , P 5 , and P 7 twist about 81°–89°. The effect of twisted architectures and connectors in optical and electrochemical properties for P 1 – P 7 have been discussed by comparing with copolymers P 1 and P 2 , which possess single bond or ether spacer as connectors. From cyclic voltammograms, the torsion in P 3 , P 5 , and P 7 confines electron delocalization and leads to simultaneously enhanced hole and electron affinity as compared to those of P 1 and P 2 . Furthermore, double‐layer light‐emitting diodes with a configuration of ITO/PEDOT:PSS/ P 1 – P 7 /Al all reveal green–yellow electroluminescence with maximum luminance at 8–320 cd/m² and their performances are greatly influenced by the connector's structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4514–4531, 2006