Synthesis and chemosensing behavior of fluorene‐based alternating copolymers containing ether side chains and Si–vinylene units in the main chain

Alternating copolymerization of 9,9‐bis(3,6,9‐trioxadecyl)‐2,7‐dibromofluorene (ODFl) or 9,9‐bis(3,6‐dioxaheptyl)‐2,7‐dibromofluorene with Si containing divinyl compounds, divinyldiphenylsilane (VPS), or divinyldimethylsilane (VMS) is investigated using the Mizoroki–Heck reaction with palladium(II) acetate. The corresponding alternating copolymer is obtained in the copolymerization of ODFl with VPS. The copolymerization of ODFl with VMS yields low molecular weight oligomers. Optical properties of the ODFl–VPS copolymer have been investigated with UV–vis absorption and photoluminescence (PL) spectroscopy. The ODFl–VPS copolymer shows absorption peaks due to π–π* transition and intramolecular charge transfer through σ–π moiety at around 330 and 360–400 nm, respectively. An emission peak is observed at 450 nm in the PL spectrum of the ODFl–VPS copolymer, and the PL quantum yield is 0.19. The PL spectroscopy of ODFl–VPS copolymer is investigated in the presence of Li⁺, Na⁺, and K⁺, and the intensity of emission peak is decreased by those metal cations, especially by Na⁺. © 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     

Synthesis and characterization of poly(fluorene)‐based copolymers containing various 1,3,4‐oxadiazole pendants

A series of soluble alternating poly(fluorene)‐based copolymers containing electron‐transporting 1,3,4‐oxadiazole (OXD) and hole‐transporting carbazole pendants attached to the C‐9 position of fluorene units by long alkyl spacers were synthesized. These copolymers possess mesogenic and nonmesogenic pendants attached to a rigid mesogenic poly(fluorene) (PF) backbone. All these polymers exhibit glass‐forming liquid crystalline properties, including the nematic and smectic A (SmA) phases, and reveal much wider mesophasic temperature ranges than that of PF. The thermal properties and mesomorphism of these conjugated polymers are mainly affected by the nature of these pendants, and thus the mesophasic temperature ranges and glass‐forming properties are greatly enhanced by introducing the OXD pendants. In addition, the tendencies of crystallization and aggregation of PF are also suppressed by introducing the OXD pendants. A single layer device with P4 as an emitter shows a turn‐on voltage of 5 V and a bright luminescence of 2694 cd/m² at 11 V with a power efficiency of 1.28 cd/A at 100 mA/cm². © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2700–2711, 2005     

Synthesis and characterization of nitrogen‐linked carbazole‐containing fluorescent polymers

We have prepared four light‐emitting polymers bearing a chromophore composed of carbazole and fluorene by the Suzuki coupling polycondensation. Two nonconjugated polymers (P3CzBFXy and P2CzFXy) had a chromophore tethered by the p‐xylylene spacer, whose connection point between carbazole and fluorene in addition to the number of fluorene unit was systematically changed to investigate the emission wavelength and intensity. The red‐shifted absorption and emission maximum wavelengths together with the improved fluorescence quantum yield of polymers P3CzBFXy and P2CzFXy indicate that the increment of the number of para‐connected benzene rings included in the chromophore effectively extends the conjugation length. The fact that polymer P3CzBFXy has longer wavelength absorption and emission spectra also indicates the interaction of the carbazole nitrogen lone pair with the oligophenylene moiety. Other two polymers P3CzFPy and P3CzFPym having the heterocycle directly bound to the carbazole nitrogen were prepared to know the character of the carbazole nitrogen lone pair and their influence on the fluorescence behavior. The fluorescence spectra of polymer P3CzFPym bearing the pyrimidine ring gradually red‐shifted in conjunction with the decrease of fluorescence quantum yield on going from toluene solution to CHCl₃ solution because of the intramolecular charge transfer at the excited state. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3729–3735, 2010     

Synthesis and characterization of alternating copolymers containing triphenylamine as hole‐transporting units

A series of light‐emitting poly(p‐phenylene vinylene)s with triphenylamine units as hole‐transporting moieties in the main chain were synthesized via Wittig condensation in good yields. The newly formed vinylene double bonds possessed a trans configuration, which was confirmed by Fourier transform infrared and NMR spectroscopy. The high glass‐transition temperature (83–155 °C) and high decomposition temperature (>300 °C) suggested that the resulting copolymers possessed high thermal stability. These copolymers, especially TAAPV1, possessed a high weight‐average molecular weight (47,144) and a low polydispersity index (1.55). All the copolymers could be dissolved in common organic solvents, such as tetrahydrofuran (THF), CHCl₃, CH₂Cl₂, and toluene, and exhibited intense photoluminescence in THF (the emission maxima were located from 478 to 535 nm) and in film (from 478 to 578 nm). The low onsets of the oxidation potential (0.6–0.75 V) suggested that the alternating copolymers possessed a good hole‐transporting property due to the incorporation of triphenylamine moieties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3278–3286, 2001     

Random fluorene copolymers with on‐chain quinoxaline acceptor units

Two series of novel random polyfluorene copolymers containing quinoxaline units were prepared by stressing the coupling according to Yamamoto. The first series contains 2,3‐bis‐(4′‐tert‐butyl‐biphenyl‐4‐yl)benzo[g]quinoxaline and the second series 2,3‐bis‐(4′‐tert‐butyl‐biphenyl‐4‐yl)quinoxaline as energy accepting unit. The copolymers were identified by gel permeation chromatography, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Thermal properties were analyzed by thermal gravimetric analysis and differential scanning calorimetry revealing amorphous copolymers that are stable up to 430 °C. The morphology was investigated using atomic force microscopy. The optical properties in solutions and thin films were analyzed. Furthermore, the thin film electro‐optical properties were determined in monolayer polymer light‐emitting devices. Single layer devices were built with efficiencies ranging from 0.15 to 2.0 cd/A. For the random copolymers with 5 mol % benzo[g]quinoxazoline in the polyfluorene backbone some threefold efficiency enhancement from 1.1 to 3.0 cd/A was achieved by utilizing an ultra thin interlayer of poly(9,9‐di‐n‐octylfluorene‐2,7‐diyl)‐alt‐[1,4‐phenylene‐(4‐sec‐butylphenylimino)‐1,4‐phenylene] between PEDOT:PSS and the emissive random copolymer layer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4773–4785, 2007     

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     

Synthesis,characterization, and electroluminescence of fluorene and carbazole‐based blue light‐emitting polymers with different noncoplanar molecular architectures

In order to investigate the explicit optoelectronic variations of the photoluminescent polymer with sterically hindered side chains, three novel alternate polymers (P0, P1, and P2) based on fluorene and carbazole moieties were successfully synthesized through Suzuki coupling reaction. The molecular structures of the polymers were fully characterized by ¹H‐NMR, ¹³C‐NMR, elemental analysis, and gel permeation chromatograph, respectively. The photophysical properties, thermal stability, and energy band gaps of polymers P0, P1, and P2 were further examined through UV–vis absorption, photoluminescent spectra, differential scanning calorimetry, thermogravimetric analysis, and cyclic voltammetry. The experimental results indicated that the polymers took on wide band gaps of about 3.50 eV with deep blue emission in thin solid films. These polymers were found to show a high thermal stability with decomposition temperatures at 5% weight loss of the compounds in the range of 353–416 °C. Blue light‐emitting electroluminescent devices of the most branched polymer P2 with highest light‐emitting efficiency as emitting layers were characterized, which showed obviously improved spectral stabilities with respect to the parent polyfluorene materials. In conclusion, we have established an effective method to improve the spectral stabilities of polyfluorene material by synthesizing the zigzag‐shaped copolymer of fluorene and carbazole with sterically hindered pendant moieties of different molecular sizes. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of polyethylene and polypropylene containing fluorene units in the side chain

Copolymerizations of ethylene or propylene and allyl monomers containing 9‐fluorenyl group, diallyl‐di‐9‐fluorenylsilane (DAFS), 9,9‐diallylfluorene (DAF), and 9‐allylfluorene (AF), were investigated with various zirconocene catalysts using methylaluminoxane as a cocatalyst. The bridged zirconocene catalysts, especially a syndioselective catalyst, showed a higher reactivity for all the comonomers than the nonbridged catalysts. DAFS was mainly incorporated into the polymer chain via cyclization insertion, whereas DAF was copolymerized via both 1,2‐ and cyclization insertions. Cyclization selectivity, ratio of cyclized insertion unit, of DAF in the copolymerization with propylene was higher than that in the copolymerization with ethylene. Copolymerization with AF yielded low‐molecular weight copolymer because of frequent chain transfer reaction. Optical properties of the propylene based‐copolymers were investigated by UV‐vis and photoluminescence spectroscopy, and absorption‐ and emission‐derived from fluorenyl groups were detected in the copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3542–3552, 2010     

Theoretical studies on the electronic and optical properties of two new alternating fluorene/carbazole copolymers

Poly(fluorene)-type materials are widely used in polymer-based emitting devices. During operation there appears, however, an additional emission peak at around 2.3 eV, leading to both a color instability and reduced efficiency. The incorporation of the carbazole units has been proven to efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate two series of alternating fluorene/carbazole oligomers and copolymers poly[2,7-(N-(2-methyl)-carbazole)-co-alt-2,7-m(9,9-dimethylfluorene)], namely, PFmCz (m = 1,2) and gain a detailed understanding of the influence of carbazole units on the electronic and optical properties of fluorene derivatives. The electronic properties of the neutral molecules, HOMO-LUMO gaps (Delta(H-L)), in addition to the positive and negative ions, are studied using B3LYP functional. The lowest excitation energies (E(g)s) and the maximal absorption wavelength lambda(abs) of PFmCz (m = 1,2) are studied, employing the time-dependent density functional theory (TD-DFT). The properties of the two copolymers, such as Delta(H-L), E(g), IPs, and EAs were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/n = 0). The outcomes showed that the carbazole unit is a good electron-donating moiety for electronic materials, and the incorporation of carbazole into the polyfluorene (PF) backbone resulted in a broadened energy gap and a blue shift of both the absorption and photoluminescence emission peaks. Most importantly, the HOMO energies of PF1Cz and PF2Cz are both a higher average (0.4 eV) than polyfluorene (PF), which directly results in the decreasing of IPs of about 0.2 eV more than PF, indicating that the carbazole units have significantly improved the hole injection properties of the copolymers. In addition, the energy gap tends to broaden and the absorption and emission peaks are gradually blue-shifted to shorter wavelengths with an increase in the carbazole content in the copolymers. This is due to the interruption of the longer conjugation length of the backbone in the (F1Cz)(n) series.     

Synthesis and properties of conjugated copolycondensates consisting of carbazole‐2,7‐diyl and fluorene‐2,7‐diyl

Carbazole and fluorene‐based random and alternating copolycondensates were synthesized to develop high‐performance blue light‐emitting polymers by improving electron injection ability of poly(N‐aryl‐2,7‐carbazole)s that showed intense blue electroluminescence (EL) with good hole‐injection and ‐transport ability. These copolycondensates absorbed light energy at about λ_max = 390 nm in CHCl₃ and 400 nm in film state, and fluoresced at about λ_max = 417 nm in CHCl₃ and 430 nm in the thin film state. Energy gaps between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of them were about 2.9 eV, and the energy levels of LUMO situated lower than that of corresponding polycarbazole. Polymer light‐emitting diode devices having configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate)/polymer/CsF/Al using the copolycondensates, poly(N‐arylcarbazole‐2,7‐diyl), and poly(9,9‐dialkylfluorene‐2,7‐diyl), emitted bluish EL at operating voltages lower than 7 V. The device embedded the random copolycondensate showed notably higher performance with maximum luminance of 31,200 cd m^?2 at 11.0 V, and the current efficiencies observed under operating voltages lower than 7 V were higher than those of the other devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

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 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     

Synthesis and properties of conjugated polymers containing 3,9‐ and 2,9‐linked carbazole units in the main chain

Novel conjugated polymers containing 3,9‐ or 2,9‐linked carbazole units in the main chain were synthesized by the polycondensation of ethynyl‐ and iodo‐substituted 9‐arylenecarbazolylene monomers, and their optical and electrical properties were studied. Polymers with weight‐average molecular weights of 3400–12,000 were obtained in 76–99% yields by the Sonogashira coupling polycondensation in piperidine or tetrahydrofuran (THF)/piperidine at 30 °C for 48 h. All the 3,9‐linked polymers absorbed light around 300 nm. The para‐phenylene‐linked polymer also absorbed light around 350 nm, while meta‐phenylene‐linked one did not. The 3,9‐linked polymers absorbed light at a wavelength longer than the 2,9‐linked one. The polymers emitted blue fluorescence with high quantum yields (0.21–0.78) upon excitation at the absorption maxima. The polymers were oxidized around 0.6 V, and reduced around 0.5 V. Poly( 1 ) showed the dark conductivity of 3.7 × 10^?11 S/cm (10³ V/cm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3506–3517, 2009     

Random poly(fluorenylene‐vinylene)s containing 3,7‐Dibenzothiophene‐5,5‐dioxide units: Synthesis,photophysical, and electroluminescence properties

The synthesis of new random poly(arylene‐vinylene)s containing the electron withdrawing 3,7‐dibenzothiophene‐5,5‐dioxide unit was achieved by the Suzuki–Heck cascade polymerization reaction. The properties of poly[9,9‐bis(2‐ethylhexyl)‐2,7‐fluorenylene‐vinylene‐co‐3,7‐dibenzothiophene‐5,5‐dioxide‐vinylene] (50/50 mol/mol, P1 ) and poly[1,4‐bis(2‐ethylhexyloxy)‐2,5‐phenylene‐vinylene‐co‐3,7‐dibenzothiophene‐5,5‐dioxide‐vinylene] (50/50 mol/mol, P2 ) were compared with those of terpolymers obtained by combining the fluorene, dibenzothiophene, and 1,4‐bis(2‐ethylexyloxy)benzene in 20/40/40 ( P3 ), 50/25/25 ( P4 ), and 80/10/10 ( P5 ) molar ratios. The polymers were characterized by ¹H NMR and IR, whereas their thermal properties were investigated by TGA and DSC. Polymers P1–5 are blue–green emitters in solution (λ_em between 481 and 521 nm) whereas a profound red shift observed in the solid state is emission (λ_em from 578 to 608 nm) that can be attributed both to the charge transfer stabilization exerted by the polar medium and to intermolecular interactions occurring in the solid state. Cyclic voltammetry permitted the evaluation of the ionization potentials and also revealed a quasi‐reversible behavior in the reduction scans for the polymers ( P1–4 ) containing the higher amounts of 3,7‐dibenzothiophene‐5,5‐dioxide units. Electroluminescent devices with both ITO/PEDOT‐PSS/ P1–5 /Ca/Al (Type I) and ITO/PEDOT‐PSS/ P1–5 /Alq₃/Ca/Al (Type II) configuration were fabricated showing a yellow to yellow–green emission. In the case of P4 , a luminance of 1835 cd/m² and an efficiency of 0.25 cd/A at 14 V were obtained for the Type II devices. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2093–2104, 2009     

Synthesis and properties of carbazole‐layered polymers

New aromatic ring‐layered polymers consisting of carbazole as a layered aromatic group and xanthene as a scaffold were designed and synthesized via the Sonogashira–Hagihara coupling reaction. Their optical and electrochemical behaviors were investigated in detail; the results showed that these polymers could be used as hole‐transporting materials. Polymers with nitrobenzene moieties at the polymer chain ends quenched the emission from the layered carbazoles to the nitrobenzene termini; thus, the polymers acted as the molecular wire that transferred photoexcited energy and/or electrons to the polymer termini. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4279–4288, 2009     

Synthesis and properties of conjugated polymers containing 3,9‐carbazolylene and silylenevinylene moieties in the main chain

Novel conjugated polymers containing 3,9‐carbazolylene and silylenevinylene moieties were synthesized by the hydrosilylation polymerization of 1,4‐bis(3‐ethynyl‐9‐carbazolyl)benzene ( 1 ) with various bis(hydrosilane)s or dihydrosilanes using a rhodium catalyst. Polymers with weight‐average molecular weights ranging from 5400 to 20,000 were obtained in 55–97% yields by the polyaddition with a rhodium catalyst in toluene at 25 °C for 24 h. All the polymers were soluble in CHCl₃ and THF, and had predominantly trans‐structures. The polymers exhibited λ_max at a longer wavelength region than 1 , and emitted fluorescence in 14–50% quantumn yields. The polymers were oxidized and reduced in the region of 0.4–1.6 V, and thermally stable up to 200 °C under air. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1815–1821, 2010     

Synthesis and characterization of new blue‐light‐emitting polymers based on PPP and PPV having fluorene pendant at vinyl bridge

The new poly(arylene vinylene) derivatives, which are composed of biphenylene vinylene phenylene vinylene, biphenylene vinylene m‐phenylene vinylene, terphenylene vinylene phenylene vinylene, and terphenylene vinylene m‐phenylene vinylene as backbone and bulky fluorene pendants at each vinyl bridge, were designed, synthesized, and characterized. The obtained polymers showed weight‐average molecular weights of 11,100–39,800 with polydispersity indexes ranging from 1.5 to 2.1. The resulting polymers were amorphous with high thermal stability and readily soluble in common organic solvents. The obtained polymers showed blue emission (λ_max = 456–475 nm) in PL spectra, and polymer 4 containing terphenylene vinylene m‐phenylene vinylene showed the most blue shifted blue emission (λ_max = 456 nm). The double layer light‐emitting diode devices fabricated by using obtained polymers as emitter emitted bright blue light. The device showed turn on voltage around 6.5 V and brightness of 70–250 cd/m². © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4923–4931, 2006     

Synthesis and characterization of fluorene‐based copolymers containing siloxane or distilbene moieties on their main chain

Two novel types of polyfluorene copolymers containing siloxane linkages or distilbene moieties on their main‐chains were synthesized by Ni(0)‐mediated Yamamoto coupling polymerization. These polymers, designated P2Silo05, P2Silo15, PF‐P02, and PF‐P05 were prepared by copolymerization between 2,7‐dibromo‐9,9′‐dihexylfluorene and bis(bromobenzene)‐terminated disiloxane monomer (for P2Silo05 and P2Silo15) or dibromodistilbene monomer (for PF‐P02 and PF‐P05). All of the polymers were highly soluble in common organic solvents such as chloroform, toluene, and p‐xylene. The glass transition temperatures of the polymers were between 92 and 113 °C, and the decomposition temperatures for a 5% weight loss (T_d) were above 420 °C for all of the polymers, demonstrating high thermal stability. The molecular weight (M_w) of the polymers ranged from 4.2 × 10⁴ to 8.8 × 10⁴. The blue shift of the maximum in the UV‐visible absorption was greater in polymers with a higher molar percentage of siloxane linkages or distilbene moieties than in homo poly (dihexylfluorene) (PDHF). However, the photoluminescence spectra of the polymers were similar to those of PDHF in terms of the onsets and patterns. Single‐layer light‐emitting diodes were fabricated with a configuration of ITO/PEDOT:PSS/polymers/Ca/Al. The maximum electroluminescence emission wavelengths of the polymers were 425–450 nm, corresponding to pure blue light. The CIE co‐ordinates of the polyfluorenes containing siloxane linkages or distilbene moieties ranged from (0.21, 0.21) to (0.17, 0.10), indicating deeper blue light than that of PDHF {CIE co‐ordinates of (0.25, 0.29)}, with P2Silo15 giving the deepest blue‐light {CIE co‐ordinates of (0.17, 0.10)}. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1595–1608, 2009     

Synthesis of poly(p‐phenylene vinylene)‐ and poly(phenylene ethynylene)‐based polymers containing p‐terphenyl in the main chain with alkoxyphenyl side groups

Starting from the pyrylium salt and following a facile synthetic route, we synthesized and polymerized 4,4″‐diiodo‐2′,6′‐di[4‐(2′‐ethylhexyl)oxy]phenyl‐p‐terphenyl with p‐divinylbenzene or p‐diethynylbenzene. The resulting polymers had moderate molecular weights, were amorphous, and dissolved in tetrahydrofuran and chloroform, with glass‐transition temperatures of 120–131 °C. The polymers behaved as violet‐blue‐emitting materials with photoluminescence maxima around 420 and 450 nm in solution and in thin films, respectively. They possessed well‐defined chromophores resulting from steric interactions in the polymer chain. The photoluminescence quantum yields were up to 0.29. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2591–2600, 2002