Synthesis, Characterization, and Electroluminescence of Novel Copolyfluorenes and Their Applications in White Light Emission

New copolyfluorenes (PC8OF0-PC8OF50) comprised of 9,9-dioctylfluorene and jacketed units 2,5-bis[(5-octyloxy-phenyl)-1,3,4-oxadiazole]-1-(3,5-dibromophenyl)-benzene (35C8) were synthesized by palladium-catalyzed Suzuki coupling reaction. They were characterized by molecular weight determination, (1)H NMR, elemental analysis, DSC, TGA, absorption and emission spectroscopy, and cyclic voltammetry (CV). These copolymers were readily soluble in common organic solvents and exhibited high glass transition temperature and thermal stability.The copolymer films showed absorption peaks from 381 nm to 351 nm, and PL peaks from 432 nm to 421 nm with a blue shift originated from 35C8 units. Both the HOMO energy levels and LUMO levels changed little as the content of 35C8 units increased (-5.59 eV to -5.48 eV and -2.60 eV to -2.49 eV). Electroluminescent devices: ITO/PEDOT:PSS[poly(ethylenedioxythiophene):polystyrenesulfonate]/polymer/Ca (25 nm)/ Ag(80 nm) (a), ITO/PEDOT:PSS/polymer/TPBI [1,3,5- tris(N-phenylbenzimidazol-2-yl)benzene](15 nm)/Mg:Ag(10:1, wt)/Ag (b), and ITO/PEDOT:PSS/PVK[Poly(N-vinyl-carbazole)]/polymer/TPBI(15 nm)/Ca(25 nm)/Ag(80 nm) (c) were fabricated to investigate the influence of jacketed contents and device architectures on emission characteristics. The maximum brightness and current efficiency of the PC8OF25 device (5097.8 cd/m(2) and 0.484 cd/A) surpassed those of the PC8OF0 device (3122.8 cd/m(2) and 0.416 cd/A). The EL emissions of PC8OF0 - PC8OF50 were pure blue and low-energy excimer emission bands were successfully suppressed, indicating that these copolymers could be good candidates for blue light-emitting materials. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4555-4565, 2009Polymer ScienceSCI(E)EI8ARTICLE184555-45654