Synthesis and light emitting properties of polyacetylenes having pendent fluorene groups

Abstract

Five novel fluorene-containing polymers, poly[(9,9-dimethylfluoren-2-yl)acetylenel (PFA1), poly[(1-pentyl-2-(9,9-dimethylfluoren-2-yl)acetylene) (PFA2), poly[1-decyl-2-(9,9-dimethylfluoren-2-yl)acetylene] (PFA3), poly[1-phenyl-2-(9,9-dimethylfluoren-2-yl)acetylenel (PFA4), and poly[1-(3,4-difluorophenyl)-2-(9,9-dimethylfluoren-2yl)acetylene] (PFA5) were synthesized by the polymerization of the corresponding fluorene-substituted acetylenic monomers (M1-M5), using WCl6, MoCl5, and TaCl5 as catalysts and n-Bu4Sn as a cocatalyst. The synthesized polymers were thermally stable and readily soluble in common organic solvents. The degradation temperatures for a 5% weight loss of the polymers were similar to 352-503 degrees C under nitrogen. PFA1-PFA5 show emission peaks from 402 to 590 nm. Besides, their electroluminescent properties were studied in heterostructure light-emitting diodes (LEDs), using PFA2-PFA5 as an emitting layer. The PFA5 device revealed an orange-red emission peak at 602 nm with a maximum luminescence of 923 cd/m(2) at 8 V. A device with the ITO/PEDOT/ a mixture of PFA2 (98 wt %) and PFA5 (2 wt %)/Ca/Al showed near white emission. Its maximum luminance and current efficiency are 450 cd/m(2) at 15 V and 1.3 cd/A, respectively. 0 2005 Wiley Periodicals, Inc.