Synthesis and properties of new luminescent poly(arylenevinylene) copolymers containing spirobifluorene

Two new light-emitting polymers, poly[2,2′-spirobifluorylene vinylene-alt-2,5-di-(n-buthoxy)-1,4-phenylene vinylene] (PSBF-PV) and poly[2,2′-spirobifluorylene vinylene-alt-9,9′-di-(fl-hexyl)-2,7-fluorenyl vinylene] (PSBF-FV) have been synthesized through the well-known Homer-Emons condensation between appropriate diphosphonates and dialdehydes. The polymers consist of arylenevinylene chromophores linked through 9,9′-spirobifiiorene to control the effective conjugation length and to suppress interchain aggregation. Photoluminescence maxima of PSBF-PV and PSBF-FV in thin solid film were shown at 512 and 446 nm, corresponding to green and blue-green emission, respectively. The single-layer light-emitting diodes of the two copolymers were fabricated in the configuration of ITO (indium-tin oxide)/polymer/Al, exhibiting weak emission. Better performance (luminance maxima is 846 cd/m2) was achieved using Alq3 as electron injection layer in double layer LEDs for PSBF-PV.