Macromolecules, 40, 8913-8923 (2007).Conjugated polymers are of wide current interest for applications in electronic and optoelectronic devices including organic lightemitting diodes (OLEDs), thin film transistors, and photovoltaic cells. In the field of polymer-based electroluminescent (EL) device, much interest has been paid to main-chain conducting polymers such as poly(phenylenevinylene) (PPV), poly(p-phenylene) (PPP), poly(thiophene), poly(fluorene), their copolymers and soluble derivatives because of potential application as large-area lightemitting diodes (LEDs). Poly(fluorene) (PF) with large band gaps have emerged as very promising materials for blue emission because of their unique combination of high thermal stability, high hole mobility, easy processablility, and high photoluminescence (PL) quantum yield in the solid state.In this investigation, we designed and synthesized a series of fluorene copolymers containing the DCMderivatized moiety (0.5~50 mole% in feed) which is well-known low molecular weight red-emitting materials from Eastman Kodak (DCM class). All the DCM class red dyes contain 2-pyran-4-ylidenemalononitrile (PM) derivatives as electron acceptor. We attempted to extend the conjugation length and enhance the electron affinity of the copolymers by introducing the p-phenylenevinylene segment with a cyano group onto the vinylene unit. Additionally, the side n-hexyloxy groups were incorporated to increase the solubility of the copolymers. The PL emission changed gradually with the DCM contents in the copolymers, from yellow at low ratio to red at high ratio. Furthermore, we tried to find the optimal ratio of the DCM content in the copolymer or blend, which simultaneously contained the fluorene emission (blue) and the DCM emission (yellow), to obtain the white light. This article presents the synthesis and characterization of the new DCM-containing copolyfluorenes, followed with discussions of their photo-physical, electrochemical and electroluminescent properties.

New copoly(aryl ether)s (P1-P3) containing alternate 2,5-dihexyloxy-1,4di(m-ethoxystyryl)benzene (P1, P2) or 2,5-dihexyloxy-1,4-distyrylbenzene (P3) chromophores and aromatic 1,3,4-oxadiazole (P1) or 3,3@-terphenyldicarbonitrile (P2, P3) segments were prepared by Horner reaction (P1 and P2) or nucleophilic displacement reaction (P3). They are basically amorphous materials with 5% weight-loss temperature above 410 8C. Their absorption, photoluminescence spectra, and quantum yields are dependent on the composition of the isolated fluorophores. The emissions are exclusively dominated by 1,4-distyrylbenzene segments via excitation energy transfer from electron-transporting 1,3,4-oxadiazole (P1) or 3,3@-terphenyldicarbonitrile (P2, P3) chromophores. The HOMO and LUMO energy levels have been estimated from their cyclic voltammograms, and the observations confirm that oxidation and reduction start from the emitting 1,4-distyrylbenzene and electron-transporting segments, respectively, indicating that both carriers affinity can be enhanced simultaneously. Among the two-layer PLED devices (ITO/PEDOT/P1-P3/Al), P1 exhibits the best performance with a turn-on field of 4 Â 10 5 V/cm and a maximum luminance of 225 cd/m 2 . However, P2 emits green-yellow light (555 nm), owing to the excimer emission. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5009-5022, 2005

A series of fluorene derivatives containing nonsymmetric and bulky aromatic groups at C‐9 position were synthesized and used for the preparation of blue‐light‐emitting copolyfluorenes (P1–P4) by the Suzuki coupling polycondensation. The copolymers were characterized by molecular weight determination, elemental analysis, differential scanning calorimeter, thermogravimetric analysis, absorption and emission spectroscopy, cyclic voltammetry, and differential pulse voltammetry. Their decomposition temperatures and glass transition temperatures are 423–441 °C and >120 °C, respectively. In film state, the copolyfluorenes exhibit blue photoluminescence at 425–450 nm, which remains almost unchanged after annealing at 200 °C in air for 60 min. Polymer light‐emitting diodes [ITO/PEDOT:PSS/P1–P4/Ca(50 nm)/Al(100 nm)] show stable blue‐light emission under device operation with the CIE co‐ordinates being between (0.16, 0.07) and (0.17, 0.09). The light‐emitting diodes devices from P1 and P3 containing electron‐deficient oxadiazole units display enhanced performance, with the maximum brightness and maximum current efficiency being (4510 cd/m2 and 2.40 cd/A) and (2930 cd/m2, 1.19 cd/A), respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2821–2834, 2009

Copolyfluorenes (PFR1 and PFR2), chemically doped with 0.1 and 0.025 mol % 2,5-dihexyloxy-1,4-bis(2-thienyl-2-cyanovinyl)benzene (MR chromophere) were synthesized by the Suzuki coupling reaction. The PFRs were used to fabricate whitelight-emitting devices through incomplete energy transfer. Because of the low content of the MR chromophore, the optical, thermal, and electrochemical properties of the PFRs were almost identical to those of polyfluorene, except for their photoluminescent (PL) and electroluminescent (EL) properties. The copolymer films showed PL peaks at about 428 and 570 nm originating from fluorene segments and MR chromophores, respectively. Compared with the model compound (MR), the polymer chains extended the conjugation length of the MR chromophores and exhibited a 20-48 nm red-shift in the emission band. In addition, the lower LUMO level of the MR (À3.27 eV) was expected to improve the electron injection. The EL devices [ITO/PEDOT:PSS/ PFRs/Ca (50 nm)/Al (100 nm)] showed a broad emission band, covering the entire visible region, with chromaticity coordinates of (0.36, 0.35) and (0.32, 0.30) for PFR1 and PFR2 devices, respectively. The emission color of the PFR2 device was very similar to that of a pure white light (0.33, 0.33); and the maximal brightness and current efficiency were 3011 cd/m 2 and 1.98 cd/A, respectively, which surpass those found for polyfluorene devices (1005 cd/m 2 , 0.28 cd/A).

Four copolyfluorenes chemically doped with 0.1 and 1 mol % 3,7‐bis[2‐thiophene‐2‐yl)‐2‐cyanovinyl]phenothiazine (PFPhT) or 2,5‐bis[2‐(thiophene‐2‐yl)‐2‐cyanovinyl]thiophene chromophores (PFThT) were synthesized using the Suzuki coupling reaction and applied in white‐light‐emitting devices. They were characterized by GPC, elemental analysis, DSC, TGA, optical spectra, and cyclic voltammetry. They exhibited good thermal stability (Td > 420 °C) and moderate glass transition temperatures (>95 °C). The PhT‐Br and ThT‐Br showed PL peaks at 586 and 522 nm (with a shoulder at 550 nm). In film state, PL spectra of the copolymers comprised emissions from the fluorene segments and the chromophores due to incomplete energy transfer. Both monomers exhibited low LUMO levels around −3.50 to −3.59 eV, whereas the PhT‐Br owned the higher HOMO level (−5.16 eV) due to its electron‐donating phenothiazine core. Light‐emitting diodes with a structure of ITO/PEDOT:PSS/copolymer/Ca(50 nm)/Al(100 nm) showed broad emission depending on the chromophore contents. The maximum brightness and maximum current efficiency of PFPhT2 (PFThT1) device were 8690 cd/m2 and 1.43 cd/A (7060 cd/m2 and 0.98 cd/A), respectively. White‐light emission was realized by further blending PFPhT2 with poly(9,9‐dihexylfluorene) (w/w = 10/1), with the maximum brightness and maximum current efficiency being 10,600 cd/m2 and 1.85 cd/A. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 833–844, 2009