Synthesis and light‐emitting properties of carbazole‐based copolymers bearing cyano‐substituted arylenevinylene chromophore

Two arylenevinylene compounds bearing the cyano group at α‐position ( 6 ) and β‐position ( 9 ) from the dialkoxylphenylene unit were synthesized, in which the molecular termini were functionalized with 3‐bromocarbazole. The Suzuki coupling copolymerization of these compounds with 1,4‐bis[(3′‐bromocarbazole‐9′‐yl)methylene]‐2,5‐didecyloxybenzene and 9,9‐dihexylfluorene‐2,7‐bis(boronic acid) was carried out to obtain copolymers ( cp67 and cp97 ) containing the cyano‐substituted arylenevinylene fluorophore of 7 mol %. Model compounds ( 6 ′ and 9 ′) corresponding to the arylenevinylene fluorophore were also prepared. The UV spectra of copolymers resembled that of homopolymer hp with no arylenevinylene segment in both CHCl₃ solution and thin film. The emission maxima of copolymers in CHCl₃ (394 nm) agreed with that of homopolymer indicating that the emission bands originated from the carbazole‐fluorene‐carbazole segment. The emission maximum wavelength of copolymer cp67 in thin film (477 nm) indicated fluorescence from the cyano‐substituted arylenevinylene fluorophore because of the occurrence of fluorescence resonance electron transfer. In contrast, copolymer cp97 showed fluorescence at 528 nm to suggest the formation of a new emissive species such as a charge‐transfer complex (exciplex). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 91–98, 2010     

Significantly improved photovoltaic performances of the dithiophene‐benzothiadiazole‐alt‐fluorene copolymers by incorporating carbazole units in fluorene moiety

To exploit an effective way to improve polymeric photovoltaic performance, a series of dithiophene‐benzothiadiazole‐alt‐fluorene copolymers containing carbazole groups at C‐9 positions of the alternating fluorene units (PFO‐FCz‐DBT) were synthesized and characterized. The effect of the carbazole groups on the optophysical, electrochemical, and photovoltaic properties of these copolymers was investigated. By comparison, this type of copolymers with carbazole units exhibited significantly improved photovoltaic properties than poly(2,7‐(9,9‐dioctyl‐fluorene)‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole) (PFO‐DBT) in the bulk heterojunction solar cells. A maximum power‐conversion efficiency (PCE) of 2.41% and a highest short‐circuit current density (J_sc) of 9.68 mA cm^?2 were obtained for the PFO‐FCz‐DBT30, which are about two times higher than the corresponding levels for the PFO‐DBT30. This work demonstrated that introducing a hole‐transporting carbazole unit into copolymer is a simple and effective method to improve the J_sc and PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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     

Incorporation of fluorene‐based emitting polymers into silica

Novel polyfluorene copolymers with pendant hydroxyl groups, poly[2,7‐(9,9‐dihexylfluorene)‐2,7‐(9,9‐bis(6‐hydroxyhexyl)fluorene)‐co‐2,7‐(9,9‐dihexylfluorene)‐1,4‐phenylene] (PFP‐OH) and poly[2,7‐(9,9‐dihexylfluorene)‐2,7‐(9,9‐bis(6‐hydroxyhexyl)fluorene)‐co‐2,7‐(9,9‐dihexylfluorene)‐4,7‐(2,1,3‐benzothiadiazole)] (PFBT‐OH) were prepared. Acid‐catalyzed polycondensations of tetraethoxysilane were carried out in the presence of these polymers to obtain homogeneous hybrids. Photoluminescence spectra of these hybrids suggested the polymers were immobilized in silica matrix retaining their π‐conjugated structures. Further, hybrids of coat film were prepared utilizing perhydropolysilazane as a silica precursor. Their optical properties were examined. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Parameters influencing the molecular weight of 3,6‐carbazole‐based D‐π‐A‐type copolymers

Condensation copolymerization reactions of carbazole 3,6‐diboronate with 4,7‐bis(5‐bromo‐2‐thienyl)‐2,1,3‐benzothiadiazole (DTBT) only produce low‐molecular‐weight donor (D)‐π‐acceptor (A) copolymers. High‐molecular‐weight copolymers for use in optoelectronic devices are necessary for achieving extended π‐conjugation and for controlling the copolymer processibility. To elucidate the cause of the persistently low molecular weight, we synthesized three 3,6‐carbazole‐based D‐A copolymers using copolymerizations of N‐9′‐heptadecanyl‐3,6‐carbazole with DTBT, N‐9′{2‐[2‐(2‐methoxy‐ethoxy)‐ethoxy]‐ethyl}‐3,‐6‐carbazole with DTBT, and N‐9′‐heptadecanyl‐3,6‐carbazole with alkyl‐substituted DTBT. We investigated several parameters for their influence on molecular copolymer weight, including the conformation of the chain during growth, the solubility of the monomers, and the dihedral angles between the donor and acceptor units. Size exclusion chromatography, UV–vis absorption spectroscopy, and computational studies revealed that the low molecular weights of 3,6‐carbazole‐based D‐A copolymers resulted from conjugation breaks and the resulting high coplanarity, which led to strong interactions between polymer chains. These interactions limited formation of high‐molecular‐weight‐copolymers during copolymerization. The strong intermolecular interactions of the 3,6‐carbazole moiety were exploited by incorporating 3,6‐carbazole units into poly[9′,9′‐dioctyl‐2,7‐flourene‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] prepared from 9′,9′‐dioctyl‐2,7‐flourene and DTBT. Interestingly, the number average molecular weight increased gradually with increasing 2,7‐fluorene monomer content but the number of conjugation breaks was a range of 6–7. The hole mobilities of the copolymers were studied for comparison purposes. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and fluorescent properties of conjugated copolymers containing maleimide and fluorene units at the main chain

Yamamoto or Suzuki–Miyaura coupling polymerizations of 2,3‐diiodo‐N‐cyclohexylmaleimide with fluorene derivatives (2,7‐dibromo‐9,9′‐dihexylfluorene and 9,9′‐dihexylfluorene‐2,7‐diboronic acid) were carried out. The number‐average molecular weights (M_n) of the resulting copolymers were 2600–3500 by gel permeation chromatography analysis. The fluorescence emission of the alternating copolymer showed the emission maxima at 551 nm in THF. On the other hand, the random copolymers showed the bimodal emission peaks at 418–420 and 555–557 nm region, respectively. The fluorescence peaks of the random copolymers on the long wavelength region (555–557 nm) were attributed to the conjugated neighboring N‐cyclohexylmaleimide‐9,9′‐dihexylfluorene units in the polymer main chain. Furthermore, the copolymers exhibited the fluorescence solvatochromism by the difference of the polarity of solvents. The alternating and random copolymers showed the different fluorescence solvatochromism, and the emission colors are distinguishable by the naked eye, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4945–4956     

High‐efficiency,electrophosphorescent polymers with porphyrin–platinum complexes in the conjugated backbone: Synthesis and device performance

A series of soluble, conjugated, electrophosphorescent copolymers with (meso‐tetraphenylporphyrinato‐κ⁴N)platinum(II) (PtTPP) complexes incorporated into the polymer main chain were synthesized through the copolymerization of narrow‐band‐gap monomeric porphyrin–platinum(II) complexes and wide‐band‐gap dialkyl‐substituted fluorene monomers by a modified Suzuki coupling reaction. The study of the photoluminescence decay indicated that poly[2,7‐(9,9‐dioctylfluorene)‐co‐2,12‐((meso‐tetraphenylporphyrinato‐κ⁴N)platinum(II))] (PFO–PtTPP) was a triplet emitter. The electroluminescence emission from the fluorene segment was completely quenched for copolymers with PtTPP contents as low as 0.5 mol %. The PFO–PtTPP copolymers emitted deep red light. The device based on the porphyrin–platinum(II) copolymer PFO–5PtTPP (with 5 mol % PtTPP in the copolymer) showed the highest external quantum efficiency of 1.95% with an emission peak at 684 nm in an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polyvinylcarbazole (PVK)/70:30 (w/w) PFO–5PtTPP: 2‐(biphenyl‐4‐yl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole/Ba/Al device configuration. In comparison with the PFO–PtTPP copolymers synthesized via a postpolymerization metalation route, copolymerization from Pt metal complexes proved to be a more efficient synthetic route for high‐efficiency electrophosphorescent polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4174–4186, 2006     

Light‐emitting copolymers based on fluorene and selenophene—Comparative studies with its sulfur analogue: Poly(fluorene‐co‐thiophene)

A series of soluble conjugated copolymers derived from 9,9‐dioctylfluorene (FO) and selenophene (SeH) was synthesized by a palladium‐catalyzed Suzuki coupling reaction with various feed ratios of SeH to FO less than or equal to 50%. The efficient energy transfer from fluorene segments to narrow band‐gap selenophene sites was observed. In comparison with the very well studied copolymer poly(fluorene‐co‐thiophene), poly(9,9‐dioctylfluorene‐co‐selenophene) (PFO‐SeH) shows redshifted photoluminescence (PL) and electroluminescence (EL) emission. PL spectra of the PFO‐SeH copolymers show a significant redshift along with increasing selenophene content in the copolymers and also with increasing polymer concentration in solution. PL quantum efficiency of the selenophene‐containing PFO copolymer is much lower than that of corresponding PFO‐thiophene (Th) copolymers. All these features of PFO‐SeH copolymers can be explained by the difference in aromaticity of selenophene and thiophene heterocycles and the heavy atom effect of Se in comparison with S‐atoms. The device fabricated with PFO‐SeH15 as the emissive layer exhibited high external quantum efficiency (0.51%) at a luminance of 1570 cd/m². Device performance is limited by electron injection and the strong quenching effect of Se atoms. Devices with PFO‐SeH copolymers blended into PFO homopolymers show significant improvement in device performance. External quantum efficiency as high as 1.7% can be obtained for PFO‐SeH30/PFO blend devices. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 823–836, 2005     

Tuning photovoltaic performance of 9,9‐dioctylfluorene‐alt‐5,7‐bis(thiophen‐2‐yl)‐2,3‐biphenylthieno[3,4‐b]pyrazine copolymeric derivatives by attaching additional donor units in pendant phenyl ring

A class of the 9,9‐dioctylfluorene‐alt‐5,7‐bis(thiophen‐2‐yl)‐2,3‐biphenylthieno [3,4‐b]pyrazine copolymeric derivatives (PFO‐3ThPz‐D) attaching additional donor (D) units in the pendant phenyl ring with a D‐A D structure was synthesized and investigated, where the additional D unit is a substituent group of fluorene, carbazole, and triphenylamine (Tpa). Their photovoltaic properties were significantly tuned by these pending donor units. Among these copolymers, the PFO‐3ThPz‐Tpa exhibited the best photovoltaic properties in the bulk heterojunction polymeric solar cells (BHJ‐PSC). The maximum power conversion efficiency (PCE) of 2.09% and the highest circuit current density (J_sc) of 7.91 mA/cm² were obtained in the cell using a blend of PFO‐3ThPz‐Tpa and PC₆₀BM (1:3, w/w) as active layer, which are 2.5 and 1.8 times higher than those corresponding levels in the other cell using the parent PFO‐3ThPz‐Ph copolymer instead of PFO‐3ThPz‐Tpa as donor, respectively. While PC₆₀BM was replaced by PC₇₀BM, the PFO‐3ThPz‐Tpa‐based BHJ‐PSC exhibited better photovoltaic properties with PCE of 3.08% and J_sc of 10.3 mA/cm². This work demonstrated that attaching donor units into the D‐A‐based copolymeric side‐chain is a simple and effective method to improve the photovoltaic properties for the resulting copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Triarylamine N‐functionalized 3,6‐linked carbazole main chain polymers and copolymers: Preparation and physical properties

The preparation of triarylamine N‐functionalized 3,6‐linked carbazole homopolymers as well as alternating copolymers with 2,5‐diphenyl‐[1,3,4]oxadiazole and benzo[1,2,5]thiadiazole was undertaken using Suzuki cross‐coupling polymerization procedures associating 3,6‐bis(4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolan‐2‐yl)‐9‐(bis[4‐(2‐butyl‐octyloxy)‐phenyl]‐amino‐phen‐4‐yl)‐carbazole and, respectively, 3,6‐dibromo‐9‐(bis[4‐(2‐butyl‐octyloxy)‐phenyl]‐amino‐phen‐4‐yl)‐carbazole, 2,5‐bis(4‐bromo‐phenyl)‐[1, 3,4]oxadiazole, and 4,7‐dibromo‐benzo[1,2,5]thiadiazole. Both the carbazole homopolymer and alternating copolymer with 2,5‐diphenyl‐[1,3,4]oxadiazole were found as wideband gap materials emitting in the blue part of the electromagnetic spectrum while the carbazole alternating copolymer with 4,7‐benzo[1,2,5]thiadiazole had a narrower band gap and emitted in the orange part of the electromagnetic spectrum. The new polymers are thermally stable up to 300 °C. A discussion of the electrochemical and optical properties of the new polymers is presented. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5957–5967, 2007.     

Novel blue‐greenish electroluminescent poly(fluorenevinylene‐alt‐dibenzothiophenevinylene)s and their model compounds

Poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐2,8‐vinylene) (PS) and poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐5,5‐dioxide‐2,8‐ vinylene) (PSO) as well as corresponding model compounds were synthesized by Heck coupling. Both the polymers and model compounds were readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane, chloroform, and toluene. The polymers showed a decomposition temperature at ～430 °C and a char yield of about 65% at 800 °C in N₂. The glass‐transition temperatures of the polymers were almost identical (75–77 °C) and higher than those of the model compounds (26–45 °C). All samples absorbed around 390 nm, and their optical band gaps were 2.69–2.85 eV. They behaved as blue‐greenish light emitting materials in both solutions and thin films, with photoluminescence emission maxima at 450–483 nm and photoluminescence quantum yields of 0.52–0.72 in solution. Organic light‐emitting diodes with an indium tin oxide/poly(ethylene dioxythiophene):poly(styrene sulfonic acid)/polymer/Mg:Ag/Ag configuration with polymers PS and PSO as emitting layers showed green electroluminescence with maxima at 530 and 540 nm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6790–6800, 2006     

Synthesis and optical and electrochemical properties of copolymers consisting of 9,9‐dihexylfluorene and aromatic triazole chromophores

Aromatic triazole chromophores were incorporated into polyfluorene in an attempt to increase electron affinity, to promote emission efficiency, and to diminish excimer formation. Poly(9,9‐dihexylfluorene) ( P1 ) and new copolymers with aromatic triazoles ( P2 – P4 ) were prepared by Suzuki coupling polymerization. In P2 , the aromatic triazole (3.8 mol %) was attached exclusively as terminal groups, whereas P3 and P4 were main‐chain copolymers containing 3.9 and 10.3 mol % aromatic triazole chromophores, respectively. The copolymers were soluble in common organic solvents and showed high decomposition temperatures (437–458 °C). The twisted structure between the triazole and fluorene increased the emission efficiency and effectively prevented excimer formation in P2 – P4 . After the introduction of the triazole units, the absorption spectra showed a blueshift (from 388 to 381 nm in chloroform) due to confined conjugation, but the photoluminescence spectra remained almost the same (417–418 nm); this was attributed to oligofluorene segments. No emission of triazole fluorophores was observed because of efficient energy transfer from the triazole to oligofluorene segments. However, incomplete energy transfer was observed in CH₃COOH. The optical stability upon thermal annealing was also improved by the incorporation of aromatic triazole segments. From cyclic voltammetry results, P2 – P4 , containing triazole groups, showed greater electron affinity (lowest unoccupied molecular orbital level = ?2.67 to ?2.71 eV) than P1 (?2.52 eV). Electroluminescence devices of P1 – P4 all exhibited excimer emissions (483–521 nm), which could also be diminished by the introduction of aromatic triazole chromophores. © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 136–146, 2007     

Synthesis and characterization of novel red‐emitting alternating copolymers based on fluorene and diketopyrrolopyrrole derivatives

Two novel alternating copolymers, poly{9,9‐dihexylfluorene‐2,7‐diyl‐alt‐2,5‐dioctyl‐3,6‐bis(4‐phenyl)pyrrolo[3,4‐c] pyrrole‐1,4‐dione} ( P1 ) and poly{9,9‐dihexylfluorene‐2,7‐diyl‐alt‐2,5‐dioctyl‐3,6‐bis(3‐phenyl)pyrrolo[3,4‐c] pyrrole‐1,4‐dione} ( P2 ), derived from 9,9‐dihexylfluorene and diketopyrrolopyrrole (DPP), have been successfully synthesized through palladium‐catalyzed Suzuki polycondensation in good yields. P1 and P2 possess moderate molecular weights and polydispersities, well‐defined structures, and excellent thermal properties with an onset decomposition temperature around 400 °C. Both P1 and P2 in thin films exhibit red photoluminescence from DPP species exclusively, with peaks at 609 and 616 nm, respectively. Cyclic voltammetry studies show that P1 and P2 have low‐lying lowest unoccupied molecular orbital energy levels at ?3.65 eV and reversible reduction processes, so these polymers may constitute another kind of red‐emitting polymer with high electron affinity. Preliminary electroluminescent results of devices with an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polymer/Ba/Al configuration reveal that P1 may be a promising candidate for red emitters with a maximum brightness of 153 cd/m² and a maximum external quantum efficiency of 0.13%, whereas the performance of P2 is relatively poor. These differences might originate from different conjugation lengths in their main chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2395–2405, 2006     

Synthesis and characterization of fluorene‐based copolymers containing benzothiadiazole derivative for light‐emitting diodes applications

Five new thermally robust electroluminescent fluorene‐based conjugated copolymers, including poly[2,7‐(9,9‐dioctylfluorene)‐co‐4,7‐{5,6‐bis(3,7‐dimethyloctyloxymethyl)‐2,1,3‐(benzothiadiazole)}] ( PFO‐P2C₁₀BT ) were synthesized and used to fabricate the efficient polymer light‐emitting diodes (PLEDs). The glass transition temperatures of the polymers were found to be higher than that of poly(9,9‐dialkylfluorenes) and are in the range 113–165 °C. We fabricated PLEDs in indium‐tin oxide/PEDOT/light‐emitting polymer/cathode configurations using either double‐layer LiF/Al or triple‐layer Alq₃/LiF/Al cathode structures. The new copolymers were found to have emission colors that vary from greenish blue (491 nm) to green (543 nm) depending on the copolymer composition. The maximum brightness and luminance efficiency of these PLEDs were found to be up to 5347 cd/m² and 1.51 cd/A at 10 V, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6762–6769, 2008     

Poly(9‐undecyl‐9‐methyl‐fluorene) and poly(9‐pentadecyl‐9‐methyl‐fluorene): Synthesis,solution structure,and effect of side chain asymmetry on aggregation behavior

We report on solution aggregates and backbone conformation of poly(9‐undecyl‐9‐methyl‐fluorene) (PF1‐11) and poly(9‐pentadecyl‐9‐methyl‐fluorene) (PF1‐15), having two different side chains compared with poly(9,9‐dihexylfluorene) (PF6) and poly(9,9‐dioctylfluorene) (PF8) with two identical side chains. In the poor solvent methylcyclohexane (MCH), X‐ray scattering indicates that PF1‐11 and PF1‐15 appear as three‐dimensional aggregates (5–10 nm wide and thick), forming ribbon‐like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two‐dimensional aggregates (>10 nm wide and 2–3 nm thick) involving ribbon‐like agglomerates (correlation lengths much greater than 100 nm). Upon heating, all aggregates undergo a gel–sol transition which occurs at lower temperatures for PF1‐11 and PF1‐15 (<60°C) than for PF6 and PF8 (>80°C). In the good solvent toluene, PF1‐11 and PF1‐15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1–2 nm). Nuclear magnetic resonance spectra in toluene‐d₈ together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1‐11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1‐15. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 826–837     

Synthesis of novel π‐conjugating polymers based on dibenzothiophene

Novel π‐conjugating polymers based on dibenzothiophene were synthesized with a novel dibenzothiophene derivative, 2,8‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)dibenzothiophene ( 1 ), prepared from dibenzothiophene. The Suzuki coupling polycondensation of 1 with 2,7‐dibromo‐9,9‐dioctylfluorene, 3,6‐dibromo‐9‐octylcarbazole, or 1,4‐dibromo‐2,5‐dioctyloxybenzene afforded the corresponding dibenzothiophene‐based polymers. The measurements of photoluminescence indicated that all these polymers exhibited blue emission in solution. The copolymer containing dibenzothiophene and 9,9‐dioctylfluorene units exhibited higher thermal stability than poly[(9,9‐dioctylfluorene‐2,7‐diyl)], although the quantum yield of copolymer was lower than that of poly[(9,9‐dioctylfluorene‐2,7‐diyl)]. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1521–1526, 2003     

Donor–acceptor rod–coil block copolymers comprising poly[2,7‐(9,9‐dihexylfluorene)‐alt‐bithiophene] and fullerene as compatibilizers for organic photovoltaic devices

The successful synthesis is described for a donor–acceptor rod–coil block copolymer comprising blocks of poly[2,7‐(9,9‐dihexylfluorene)‐alt‐bithiophene] (F6T2) and polystyrene functionalized with fullerene (PS(C₆₀)) (F6T2‐b‐PS(C₆₀)). This new material was obtained by combining Suzuki polycondensation with radical addition fragmentation chain transfer. The block copolymer was characterized by nuclear magnetic resonance, gel permeation chromatography, and optical spectroscopy methods. Photophysical data for (F6T2‐b‐PS(C₆₀)) and a related block copolymer (F6T2‐b‐PS(PCBM)) (PCBM, phenyl‐C61‐butyric acid methyl ester) are reported and their performance as compatibilizers in bulk heterojunction organic solar cells is assessed. It is demonstrated that the addition of the rod–coil block copolymers to the active layer extends the operational stability of organic photovoltaic devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 888–903     

Synthesis and characterization of fluorene‐based low‐band gap copolymers containing propylenedioxythiophene and benzothiadiazole derivatives for bulk heterojunction photovoltaic cell applications

The following noble series of soluble π‐conjugated statistical copolymers was synthesized by palladium catalyzed Suzuki polymerization: poly[(9,9‐dioctylfluorene)‐alt‐(4,7‐bis(3′,3′‐dihepyl‐3,4‐propylenedioxythienyl)‐2,1,3‐benzothiadiazole)] (PFO‐PTBT) derived from poly(9,9‐dioctylfluorene) (PFO) and poly[(4,7‐bis(3′,3′‐dihepyl‐3,4‐propylenedioxythienyl)‐2,1,3‐benzothiadiazole)] poly(heptyl₄‐PTBT). The structure and properties of these polymers were characterized using ¹H‐, ¹³C‐NMR, UV–visible spectroscopy, elemental analysis, GPC, DSC, TGA, photoluminescence (PL), and cyclic voltammetry (CV). The statistical copolymers, PFO‐PTBT (9:1, 8.4:1.6, 6.5:3.5), were soluble in common organic solvents and easily spin coated onto indium‐tin oxide (ITO) coated glass substrates. The weight‐average molecular weight (M_w) and polydispersity of the PFO‐PTBT ranged from (1.0–4.2) × 10⁴ and 1.5–2.3, respectively. Bulk heterojunction photovoltaic cells with an ITO/PEDOT/PFO‐PTBT:PCBM/LiF/Al configuration were fabricated, and the devices using PFOPTBT (6.5:3.5) showed the best performance compared with those using PFO‐PTBT (9:1, 8.4:1.6). A maximum power conversion efficiency (PCE) of 0.50% (V_oc = 0.66 V, FF = 0.29) was achieved with PFO‐PTBT (6.5:3.5). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6175–6184, 2008     

Synthesis,characterization, and preceramic properties of π‐conjugated polymers based on Ni(II) complexes of goedken's macrocycle

Nickel(II) complexes of Goedken's macrocycle bearing alkyne substituents were copolymerized with 2,7‐dibromo‐9,9‐dihexylfluorene, 2,5‐dibromo‐3‐hexylthiophene, and 1,4‐dibromo‐2,5‐bis(hexyloxy)benzene via microwave‐induced Sonogashira cross‐coupling reactions to produce copolymers 6F , 6T , and 6B . The spectroscopic and electrochemical properties of the copolymers were examined and compared to model compounds. Specifically, each polymer exhibited a nickel‐based absorption centered at about 589 nm and two π → π* transitions between 272 and 387 nm. While the copolymers did not exhibit extended π conjugation, the nature of the organic spacer did affect the high energy transitions. Furthermore, each copolymer underwent two ligand‐based one‐electron oxidations at potentials of about 0.24 V and about 0.75 V relative to the ferrocene/ferrocenium redox couple. Postpolymerization functionalization of the alkyne group in 6F with Co₂(CO)₈ afforded a novel heterobimetallic copolymer that yielded amorphous nanomaterials containing Ni/Co when pyrolyzed at 800 °C for 3 h under an atmosphere of N₂/H₂ (95:5). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3257–3266     

Suppressing charge recombination by incorporating 3,6‐carbazole into poly[9‐(heptadecan‐9‐yl)‐9H‐carbazole‐2,7‐diyl‐alt‐(5,6‐bis‐(octyloxy)‐4,7‐di(thiophen‐2‐yl)benzo[1,2,5]‐thiadiazole)‐5,5‐diyl]

A series of poly[9‐(heptadecan‐9‐yl)‐9H‐carbazole‐2,7‐diyl‐alt‐(5,6‐bis‐(octyloxy)‐4,7‐di(thiophen‐2‐yl)benzo‐[1,2,5]‐thia‐diazole)‐5,5‐diyl] compositions containing various ratios of 3,6‐carbazole was synthesized for testing in a polymer solar cell. An appropriate amount of 3,6‐carbazole units incorporated into the copolymer improved intermolecular charge transport, whereas excess amount of 3,6‐carbazole units temporarily seized on the partial negative charge generated in the conjugation breaks. We extensively studied the effects of the incorporated 3,6‐carbazole units on the intermolecular interactions, which can affect nongeminated recombination in bulk heterojunction‐polymer solar cells. These properties were investigated using photocurrent‐ and light intensity‐dependent measurements and electrochemical impedance spectroscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2047–2056