Synthesis,characterization, and properties of regioregular conjugated polymers containing quaterthiophene and an acceptor repeating units

Novel donor–acceptor type polymers consisting of alternating quaterthiophene and an electron withdrawing moiety, pyrazinyl or pyridinyl, have been prepared using Stille coupling approach with moderate yields. The polymers were highly soluble in common organic solvents such as tetrahydrofuran and chloroform. The structure and optical properties of the polymers were characterized by NMR, UV‐vis and fluorescence spectroscopy, and cyclic voltammetry, respectively. The polymer having pyrazine unit exhibited a red‐shift in both absorption and emission in comparison with those analogs containing pyridine because of strong electron withdrawing character of the pyrazinyl group. The polymer containing pyrazinyl as acceptor units also depicted decrease in its optical and electrochemical bandgap relative to those polymers containing 2,5‐ or 2,6‐pyridine moieties. The electrochemical behavior showed facile n‐doping and p‐doping properties of those polymers consisting of alternating quaterthiophene and the acceptor moiety. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2163–2171, 2009     

Synthesis and characterization of a new acceptor (n‐type) fluorinated and terminal‐functionalized polythiophene

Donor‐ or acceptor‐substituted polythiophenes have many potential applications in optoelectronics. Fluorinated polythiophenes are particularly attractive because of the presence of fluorine, which can withdraw electrons and also improve polymer chemical stability. Because of the promising future of these polymers, there has been much interest in identifying favorable synthetic routes to new fluorinated monomers and polymers. In this study, the monomer had an electron‐withdrawing fluorinated ester and was derived from 3‐thiophene carboxylic acid and 2,2,3,3,4,4,4‐heptafluoro‐1‐butanol. The synthesis of an n‐type fluorinated and terminal‐functionalized polythiophene was accomplished with the Ullmann coupling reaction. A polymer soluble in tetrahydrofuran was obtained with a molecular weight of approximately 15,000 g/mol. In solution, it exhibited a band gap of 2.4 eV, and the photoluminescent excitation and emission maxima were 370 nm and 555 nm, respectively. All peaks were bathochromically shifted when they were measured in the solid state. The glass‐transition and decomposition (in air) temperatures were 129 and 493 °C, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4280–4287, 2005     

Blue‐emitting poly[(m‐phenylene vinylene)‐alt‐(o‐phenylene vinylene)]s: The effect of regioregularity on the optical properties

Poly[(m‐phenylene vinylene)‐alt‐(o‐phenylene vinylene)]s with different contents of cis‐/trans‐CH?CH ( 3 and 6 ) have been synthesized through Wittig condensation. The polymers exhibit good solubility in common organic solvents such as toluene and tetrahydrofuran. A comparison of the optical properties has been made between 3 and its phenyl regioisomers containing either p‐phenylene or m‐phenylene units. The results show that the regiochemistry of the phenyl ring can be a useful tool for tuning the emission color of π‐conjugated polymers because the extension of π conjugation can only partially be achieved through an o‐phenylene bridge. Although both polymers 3 and 6 exhibit comparable low fluorescence quantum efficiencies (≈0.18) in solution, their films are highly luminescent, showing a broad emission band near 456 nm (blue color). Electroluminescence results show that the device of polymer 3 , which has a higher content of trans‐CH?CH linkages, is about 20 times more efficient than that of 6 . © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2650–2658, 2003     

Synthesis of carbazole‐based light‐emitting polymers incorporating 2,5‐bis(phenylethenyl)‐4‐decyloxyanisole as collateral fluorophore

The Suzuki coupling polymerization between bis(carbazole) monomer ( CzDB ) and 9,9‐dihexylfluorene‐2,7‐diboronic acid was carried out to obtain PFCz‐PEDA0 having the number‐averaged molecular weight of 7000. The absorption and emission maximum wavelengths were observed at 344 and 408 nm, respectively. The quantum yield (QY) was relatively low (0.12) because of the photo‐induced electron transfer. Subsequently, CzPEDA ‐bearing 2,5‐bis(phenylethenyl)‐4‐decyloxyanisole (PEDA) segment sandwiched with 3‐bromocarbazole units was copolymerized to give PFCz‐PEDAn (n = 05, 10, 20, 35, and 50). The content of PEDA segment in polymer could be controlled by the monomer feed ratio. In CHCl₃ solution, the absorbance at around 400 nm became larger with one isosbestic point at 370 nm, and the emission peak at 448 nm became prominent with increasing the PEDA content. The QY of polymer was increased as the PEDA content, which was a consequence of the fluorescence resonance energy transfer from carbazole‐containing chromophore (energy donor) to PEDA fluorophore (energy acceptor). In spin‐coated film, the maximum QY was obtained in PFCz‐PEDA05 having the most appropriate molar balance of energy donor and acceptor units. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8141–8148, 2008     

Structures and properties of liquid‐crystalline polymers based on laterally attached oligo p‐phenylenes

The structures and properties of liquid‐crystalline polymers containing laterally attached p‐terphenyl and p‐pentaphenyl have been studied. In contrast to their mesogenic groups, that is, p‐terphenyl and p‐pentaphenyl, the polymers have much lower crystallinity and also lower nematic‐to‐isotropic transition temperatures. The significant depression in crystallinity can be attributed to flexible chain segments laterally attached to the oligo p‐phenylene rods, which prevent close packing of the rods and thus disrupt the crystallization. The destabilization of the liquid‐crystalline phase is due to the diluting effect of the flexible polymer backbones; that is, the concentration of the mesogenic groups is reduced. The polymer containing p‐pentaphenyl can still exhibit good solubility in common solvents and emit light at about 402 nm in the solvent tetrahydrofuran. In the solid state, the emission redshifts to 418 nm, which is fairly close to the blue‐light emission. An interdigitated packing structure of mesogenic groups has been proposed to represent the structure of the polymer in the oriented state. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3394–3402, 2005     

A solution‐processible poly(p‐phenylene vinylene) without alkyl substitution: Introducing the cis‐vinylene segments in polymer chain for improved solubility,blue emission,and high efficiency

A soluble all‐aromatic poly(2,5‐diphenyl‐1,4‐phenylenevinylene) (2,5‐DP‐PPV) is synthesized by utilizing aromatic phosphonium and aldehyde monomers through Wittig reaction. The H¹ NMR and FTIR measurements indicate that over 50% content of cis‐vinylene units exist in polymer backbone. The diphenyl‐substituted benzaldehyde monomer plays an important role to enhance cis‐products (Z‐selectivity) in Wittig reactions. The twisted cis‐segments in polymer backbone reduce the interchain interactions and enhance the solubility of such all‐aromatic PPV derivative in common organic solvents. 2,5‐DP‐PPV exhibits good solubility in common organic solvents, such as tetrahydrofuran and chloroform. The polymer film exhibits a blue light emission (λ_max = 485 nm) and a very high photoluminescence efficiency of 78%. The cis‐trans photo isomerization of this polymer in solution and the impact on the optical properties are also investigated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5242–5250, 2008     

Poly[2,7‐(9,9‐dihexylfluorene)‐alt‐pyridine] with donor‐acceptor architectures: A new series of blue‐light‐emitting alternating copolymers

A novel series of well‐defined alternating poly[2,7‐(9,9‐dihexylfluorenyl)‐alt‐pyridinyl] (PDHFP) with donor‐acceptor repeat units were synthesized using palladium (0)‐catalyzed Suzuki cross‐coupling reactions in good to high yields. In this series of alternating polymers, 2, 7‐(9,9‐dihexylfluorenyl) was used as the light emitting unit, and the electron deficient pyridinyl unit was employed to provide improved electron transportation. These polymers were characterized by ¹H‐NMR and ¹³C‐NMR, gel permeation chromatography (GPC), thermal analyses, and UV‐vis and fluorescence spectroscopy. The glass transition temperature of copolymers in nitrogen ranged from 110 to 148 °C, and the copolymers showed high thermal stabilities with high decomposition temperatures in the range of 350 to 390 °C in air. The difference in linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases. Meta‐linkage (3,5‐ and 2,6‐linkage) of pyridinyl units in the polymer backbone is more favorable to polymer for pure blue emission and prevention of aggregation of polymer chain than para‐linkage (2,5‐linkage) of the pyridinyl units. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4792–4801, 2004     

Study of supramolecular side‐chain and cross‐linking polymers by complexation of various H‐donor acids with H‐acceptor copolymers containing pendent carbazole and fluorescent pyridyl units

Two H‐bonded acceptor (H‐acceptor) homopolymers 14 and 17 were successfully prepared by polymerization of fluorescent pyridyl monomers PBT and PBOT ( 12 and 13 ), which were synthesized via Sonogashira coupling and Wittig‐Horner reactions. To increase the glass transition temperatures as well as reduce the π‐π stacking of the photoluminescent (PL) H‐acceptor copolymers and their H‐bonded polymer complexes, fluorescent monomers 12 and 13 were copolymerized with N‐vinylcarbazole monomer CAZ (23) to produce H‐acceptor copolymers 15–16 and 18–19 . Supramolecular side‐chain and crosslinking polymers (i.e., H‐bonded polymer complexes) obtained by complexation of light‐emitting H‐acceptor polymers 14–19 with various proton donor (H‐donor) acids 20–22 were further characterized by DSC, POM, FTIR, XRD, and PL measurements. The mesomorphic properties can be tuned from the nematic phase in H‐acceptor homopolymers ( 14 and 17 ) to the tilted smectic C phase in their H‐bonded polymer complexes ( 14/20–21 and 17/20–22 ) by the introduction of H‐donor acids (20–22). Moreover, the PL properties of light‐emitting H‐acceptor polymers can be adjusted not only by the central structures of the conjugated pyridyl cores but also by their surrounding nonfluorescent H‐donor acids. In general, redder shifts of PL emissions in H‐bonded polymer complexes occurred when the light‐emitting H‐acceptor polymers were complexed with H‐donors having smaller pKa values. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2734–2753, 2009     

High‐efficiency blue light‐emitting polymers based on 3,6‐silafluorene and 2,7‐silafluorene

A novel blue‐emitting polymer based on 3,6‐silafluorene and 2,7‐silafluorene was synthesized via the Suzuki polycondensation. The resulting polymers are readily soluble in common organic solvents, such as toluene, xylene, THF, and chloroform. The thermal, electrochemical, photophysical, and electroluminescence properties of the resulting polymers were investigated. The device fabricated from the copolymer with a configuration of ITO/PEDOT:PSS/PVK/polymer/Ba/Al exhibited an external quantum efficiency of 1.95%, a luminous efficiency of 1.69 cd A^?1 and a maximal brightness of 6000 cd m^?2. It has been found that the incorporation of the 3,6‐silafluorene unit into the poly(2,7‐silafluorene) main chain can not only improve the color purity of the devices from the resulting copolymer but also enhance its device efficiency. Moreover, no undesired long‐wavelength green emission was observed in the PL spectra of P36‐27SiF90 compared to that of PFO with a dominating emission at 500–600 nm after thermal annealing at 200 °C for 8 h. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4941–4949, 2007     

Design,synthesis, photophysical,and electrochemical properties of DCM‐based conjugated polymers for light‐emitting devices

A series of conjugated hyperbranched polymers, hyperbranched copolymers, and linear polymers containing 2‐pyran‐4‐ylidenemalononitrile (acceptor) and triphenylamine/fluorene (donor) units were synthesized and characterized by FTIR, ¹H NMR, thermogravimetric analyses, differential scanning calorimetry, gel permeation chromatography, UV–visible, photoluminescence, and cyclic voltammetry measurements. All the polymers show red‐light emission in the range of 566–656 nm both in solution and in solid state. The quantum efficiency of the polymers was in the range of 56–82%. Among the six polymers synthesized, only polymers containing fluorene units show T_g and polymers based on triphenylamine not exhibit T_g. The band gap of these polymers were found to be reasonably low; hyperbranched copolymer containing fluorene unit shows lowest band gap of 2.18 eV due to the stabilization of LUMO energy level by the electron withdrawing ? CN groups. The thermal and solubility behavior of the polymers were found to be good. All the EL spectra of the devices (indium‐tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)/polymer/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline/tris(8‐hydroxyquinoline)aluminum)/LiF/Al) show red‐light emission, and the device fabricated with P3 and P4 shows maximum luminance and luminous efficiency of 4104 cd m^?2 and 0.55 cd Å^?1 and 3696 cd m^?2 and 0.47 cd Å^?1, respectively, indicates that they had the best carrier balance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Modular synthesis of polymers containing 2,5‐di(thiophenyl)‐N‐arylpyrrole

A modular and facile route has been developed to synthesize functionalized 2,5‐di(thiophen‐2‐yl)‐1‐H‐arylpyrroles from readily available starting materials. These units are compatible with various polymerization conditions and are versatile building blocks for conjugated polymers. The polymers show high thermal stability and solubility in a number of solvents. Characterization of the polymers reveals a correlation between molecular packing, controllable by polymer design, and charge carrier mobility. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1133–1139     

Synthesis,optical properties,and electroluminescence of conjugated poly(p‐phenylenevinylene) derivatives containing 1,3,4‐oxadiazole and pyridine rings in the main chain

Three new poly(p‐phenylenevinylene) derivatives—PO, POD, and POP—with oxadiazole and pyridine rings along the main chain were synthesized via Heck coupling. The polymers were amorphous and dissolved readily in common organic solvents. They showed relatively low glass‐transition temperatures (up to 42 °C) and satisfactory thermal stability. Solutions of the polymers emitted blue‐greenish light with photoluminescence (PL) emission maxima around 460 nm and PL quantum yields of 0.28–0.49. Thin films of the polymers displayed PL emission maxima at 461–521 nm, and their tendency to form aggregates was significantly influenced by the chemical structure. Light‐emitting diodes with polymers PO and POP, with an indium tin oxide/poly(ethylenedioxythiophene) (PEDOT)/polymer/Ca configuration, emitted yellow and green light, respectively, and this could be attributed to excimer emission. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3212–3223, 2004     

Bandgap engineering of indenofluorene‐based conjugated copolymers with pendant donor‐π‐acceptor chromophores for photovoltaic applications

Three narrow‐band‐gap conjugated copolymers based on indenofluorene and triphenylamine with pendant donor‐π‐acceptor chromophores were successfully synthesized by post‐functionalization approach. All the polymers have good solubility in common solvents and excellent thermal stability. The photophysical properties, energy levels and band gaps of the polymers were well manipulated by introducing different acceptor groups onto the end of their conjugated side chains. By using different acceptor groups, the band gaps of the polymers were narrowed from 1.86 to 1.53 eV by lowering their lowest unoccupied molecular orbital levels, whereas their relatively deep highest occupied molecular orbital levels of approximately ?5.35 eV were maintained. Bulk‐heterojunction solar cells with these polymers as electron donors and (6,6)‐phenyl‐C₇₁‐butyric acid methyl ester as acceptor showed power conversion efficiencies as high as 3.1% and high open circuit voltages more than 0.88 eV. The relationships between the performance and film morphology, energy levels, charge mobilities were discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of three new 1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl) pyrrole‐based donor polymers and their bulk heterojunction solar cell applications

A series of three new 1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole‐based polymers such as poly[1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole] ( PTPT ), poly[1,4‐(2,5‐bis(octyloxy)phenylene)‐alt‐5,5'‐(1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole)] ( PPTPT ), and poly[2,5‐(3‐octylthiophene)‐alt‐5,5'‐(1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole)] ( PTTPT ) were synthesized and characterized. The new polymers were readily soluble in common organic solvents and the thermogravimetric analysis showed that the three polymers are thermally stable with the 5% degradation temperature >379 °C. The absorption maxima of the polymers were 478, 483, and 485 nm in thin film and the optical band gaps calculated from the onset wavelength of the optical absorption were 2.15, 2.20, and 2.13 eV, respectively. Each of the polymers was investigated as an electron donor blending with PC₇₀BM as an electron acceptor in bulk heterojunction (BHJ) solar cells. BHJ solar cells were fabricated in ITO/PEDOT:PSS/polymer:PC₇₀BM/TiO_x/Al configurations. The BHJ solar cell with PPTPT :PC₇₀BM (1:5 wt %) showed the power conversion efficiency (PCE) of 1.35% (J_sc = 7.41 mA/cm², V_oc = 0.56 V, FF = 33%), measured using AM 1.5G solar simulator at 100 mW/cm² light illumination. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Fluorene copolymers containing bithiophene/2,5‐ or 2,6‐pyridine units: A study of their optical,electrochemical, and electroluminescence properties

Two alternating copolymers, poly[(2,5‐di(2‐thienyl)‐pyridine‐5,5′‐diyl)‐alt‐(9,9‐dioctylfluorene‐2,7‐diyl)], PFO‐TPy25T, and poly[(2,6‐di(2‐thienyl)‐pyridine‐5,5′‐diyl)‐alt‐(9,9‐dioctylfluorene‐2,7‐diyl)], PFO‐TPy26T, were synthesized by the Pd‐catalyzed Suzuki polymerization method. The pyridine units are present as trimeric monomers in these copolymers and have different connectivities to their two neighboring thiophenes, para‐ and meta‐linkages. We investigated the variations in the optical and electrochemical properties of the copolymers that arise from these different connectivities. The two polymers exhibit 5% weight loss above 410 °C and high glass transition temperatures (T_g: 113 °C for PFO‐TPy25T, 142 °C for PFO‐TPy26T). The UV–vis absorption maximum peaks of PFO‐TPy25T and PFO‐TPy26T in the solid state were found to be 449 and 398 nm respectively, with photoluminescence maximum peaks in the solid state of 573 and 490 nm respectively. Using cyclic voltammetry, we determined their energy band gaps: 3.08 eV for PFO‐TPy25T and 3.49 eV for PFO‐TPy25T. The cyclic voltammetry study of these polymers revealed that there are some differences. The electroluminescence (EL) properties of the copolymers were measured for the device configuration of ITO/PEDOT/polymers/Ca/Al. The device fabricated with the polymer containing 2,5‐pyridine exhibits pale orange emission, whereas the device fabricated with the polymer containing 2,6‐pyridine exhibits pale blue emission. The EL device fabricated with PFO‐TPy25T has a higher brightness (2010 cd/m²) and external quantum efficiency (0.1%) than the PFO‐TPy26T device (260 cd/m², 0.008%), because it has a smaller energy barrier to the injection of charges from PEDOT and Ca into the HOMO and LUMO levels. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4611–4620, 2006     

Deep‐red emissive conjugated poly(2,6‐BODIPY‐ethynylene)s bearing alkyl side chains

Novel deep‐red emissive poly(2,6‐BODIPY‐ethynylene)s bearing dodecyl side chains (polymers A , B , and C ) have been prepared by palladium‐catalyzed Sonogashira polymerization of 2,6‐diiodo‐functionalized BODIPY monomers with 2,6‐diethynyl‐functionalized BODIPY monomers. These polymers emit in the deep‐red region with emission maxima at up to 690 nm, and exhibit significant red shifts (up to 166 and 179 nm) of both absorption and emission maxima compared with their parent BODIPY dyes due to significant extension of π‐conjugation. These polymers possess good thermal stability with decomposition temperature between 270 and 360 °C. The polymers exhibit a little larger Stokes shifts and shorter lifetime than their corresponding BODIPY dyes. The solid state thin films of polymers A , B , and C emit in near‐infrared region between 723 and 743 nm, and show significantly red shifts (up to 57 nm) in absorption and emission maxima relative to their polymer solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5354–5366, 2009     

Optical properties of a novel fluorene‐based thermally stable conjugated polymer containing pyridine and unsymmetric carbazole groups

A new diiodo monomer containing heterocyclic pyridine and carbazole groups was synthesized via Chichibabin reaction and used in the preparation of a conjugated polymer via Suzuki coupling approach. The conjugated polymer was highly soluble in common organic solvents such as NMP, THF, dichloromethane, chloroform, toluene, xylene, and benzene at room temperature. The polymer had high glass transition temperature at 191 °C and T_d10 at 434 °C in nitrogen atmosphere. The pristine polymer exhibited the UV–vis maximum absorption at 355 nm and shifted to 420 nm after protonation. The emission of the polymer in THF solution changed from the blue region with maximum peak at 400 nm to the yellow region with maximum peak at 540 nm after protonated by HCl, and the intensity of emission depended on the concentration of acid. The polymer also showed electrochromic behavior under applied voltage. The emission color of the polymer film changed from blue (435 nm) to yellow (570 nm) when 2.5 V bias voltage was applied. The polymer also exhibited write‐once and read‐many‐times (WORM) polymer memory effect with tristable states. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 991–1002, 2009     

Narrow band gap D–A copolymer of indacenodithiophene and diketopyrrolopyrrole with deep HOMO level: Synthesis and application in field‐effect transistors and polymer solar cells

A novel fused ladder alternating D–A copolymer, PIDT–DPP, with alkyl substituted indacenodithiophene (IDT) as donor unit and diketopyrrolopyrrole (DPP) as acceptor unit, was designed and synthesized by Pd‐catalyzed Stille‐coupling method. The copolymer showed good solubility and film‐forming ability combining with good thermal stability. PIDT–DPP exhibited a broad absorption band from 350 to 900 nm with an absorption peak centered at 735 nm. The optical band gap determined from the onset of absorption of the polymer film was 1.37 eV. The highest occupied molecular orbital level of the polymer is as deep as ?5.32 eV. The solution‐processed organic field‐effect transistor (OFETs) was fabricated with bottom gate/top contact geometry. The highest FET hole mobility of PIDT–DPP reached 0.065 cm² V^?1 s^?1 with an on/off ratio of 4.6 × 10⁵. This mobility is one of the highest values for narrow band gap conjugated polymers. The power conversion efficiency of the polymer solar cell based on the polymer as donor was 1.76% with a high open circuit voltage of 0.88 V. To the best of our knowledge, this is the first report on the photovoltaic properties of alkyl substituted IDT‐based polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and electroluminescent properties of polyfluorene‐based conjugated polymers containing bipolar groups

A bipolar dibromo monomer, bis‐(4‐bromophenyl)[4‐(3,5‐diphenyl‐1,2,4‐ triazole‐4‐yl)‐phenyl]amine ( 9 ), containing electro‐rich triphenylamine and electro‐deficient 1,2,4‐triazole moieties was newly synthesized and characterized. Two fluorescent fluorene‐based conjugated copolymers ( TPAF , TPABTF ) were prepared via facile Suzuki coupling from the dibromo bipolar monomer, 4,7‐dibromo‐2,1,3‐benzothiadiazole ( BTDZ ), and 9,9‐dioctylfluorene. They were characterized by molecular weight determination, IR, NMR, DSC, TGA, solubility, absorption and photoluminescence spectra, and cyclic voltammetry. The polymers showed good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and dichlorobenzene at room temperature. They had glass transition temperatures (T_g) higher than 135 °C and 5% degradation temperatures in nitrogen atmosphere were higher than 428 °C. Single layer polymer light‐emitting diodes (PLED) of ITO/PEDOT:PSS/polymer/metal showed a blue emission at 444 nm and Commission Internationale de I'Eclairage (CIE) 1931 color coordinates of (0.16, 0.13) for TPAF . The device using TPABTF as emissive material showed electroluminescence at 542 nm with CIE1931 of (0.345, 0.625), low turn‐on voltage of 5 V, a maximum electroluminance of 696 cd/m², and a peak efficiency of 2.02 cd/A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6231–6245, 2009     

Synthesis and characterization of indeno[1,2‐b]fluorene‐based white light‐emitting copolymer

An indenofluorene‐based copolymer containing blue‐, green‐, and red light‐emitting moieties was synthesized by Suzuki polymerization and examined for application in white organic light‐emitting diodes (WOLEDs). Tetraoctylindenofluorene (IF), 2,1,3‐benzothiadiazole (BT), and 4,7‐bis(2‐thienyl)‐2,1,3‐benzothiadiazole (DBT) derivatives were used as the blue‐, green‐, and red‐light emitting structures, respectively. The number‐average molecular weight of the polymer was determined to be 25,900 g/mol with a polydispersity index of 2.02. The polymer was thermally stable (T_d = ～398 °C) and quite soluble in common organic solvents, forming an optical‐quality film by spin casting. The EL characteristics were fine‐tuned from the single copolymer through incomplete fluorescence energy transfer by adjusting the composition of the red/green/blue units in the copolymer. The EL device using the indenofluorene‐based copolymer containing 0.01 mol % BT and 0.02 mol % DBT units ( PIF‐BT01‐DBT02 ) showed a maximum brightness of 4088 cd/m² at 8 V and a maximum current efficiency of 0.36 cd/A with Commission Internationale de L'Eclairage (CIE) coordinates of (0.34, 0.32). The EL emission of PIF‐BT01‐DBT02 was stable with respect to changes in voltage. The color emitted was dependent on the thickness of the active polymer layer; layer (～60 nm) too thin was unsuitable for realizing WOLED via energy transfer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3467–3479, 2009