New series of highly phenyl‐substituted polyfluorene derivatives for polymer light‐emitting diodes

A new series of highly phenyl‐substituted polyfluorene derivatives were synthesized and characterized. The resulting polymers were amorphous and showed excellent solubility in common organic solvents, such as chloroform, tetrahydrofuran, xylene, toluene, chlorobenzene, and so forth. All possessed satisfied thermal stability with glass‐transition temperatures (T_g's) in the range of 79–115 °C. They emitted blue light with photoluminescent (PL) maximum peaks at about 408–412 nm in thin films. The PL efficiencies of the polymer films were measured around 30–33%. The highly phenylated pendants improved the T_g of polyfluorene without forming defects in the polymers and reduced their tendency to form aggregate/excimers. Polymer light‐emitting diodes were fabricated from these polymers with the configuration of indium tin oxide/polyethylenedioxythiophene:polystyrene sulfonic acid/polymer/Ba/Al, which emitted bright blue light with maximum peaks at 418–420 nm. The maximum external quantum efficiencies of these devices were 0.41–0.6%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2985–2993, 2004     

Synthesis,photophysics, structure‐tunable photoluminescence,and electrochemical properties of soluble poly(p‐phenylenevinylene)‐based polymers with adjacent 1,3,4‐oxadiazoles in the backbone

Three new poly(p‐phenylenevinylene)‐based polymers containing two 1,3,4‐oxadiazole moieties in the main chain per repeat unit were synthesized by Heck coupling. A single, double, or triple bond was introduced between the oxadiazoles to provide a means for modifying the polymer properties. The polymers were readily soluble in common organic solvents and showed T_g values lower than 50 °C. The color of the emissive light in both the solid state and the solution could be tuned by a change in the nature of the bond between the oxadiazole rings. The polymers emitted ultraviolet‐green light in solution with a photoluminescence (PL) emission maximum at 345–483 nm and blue‐green light at 458–542 nm in thin films. The PL quantum yields in solution were 0.36–0.43. The electrochemical properties are affected by the nature of the bond between the oxadiazoles as well. In polymers with a single bond between the oxadiazoles, a lower ionization potential was observed than in polymers with a double or triple bond. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3079–3090, 2005     

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     

New poly(p‐phenylene vinylene) derivatives with two oxadiazole rings per repeat unit: Synthesis,photophysical properties,electroluminescence, and metal ion recognition

Two new poly(p‐phenylene vinylene) derivatives OX1‐PPV and OX2‐PPV bearing two 1,3,4‐oxadiazole rings per repeat unit and a fully conjugated backbone with solubilizing dodecyloxy side groups were synthesized and investigated. The amorphous conjugated polymers had glass‐transition temperature values of 60–75 °C and emitted intense blue or greenish‐blue light in solution with photoluminescence (PL) emission maxima at 379–492 nm and PL quantum yields of 0.41–0.52. In the solid state they emitted yellowish‐green light with PL emission maxima at 533–555 nm. Cyclic voltammetry showed that both conjugated polymers had reversible reduction and irreversible oxidation, making them n‐type materials. The electron affinity of OX2‐PPV was estimated as 2.85 eV whereas that of OX1‐PPV was 2.75 eV. Yellow electroluminescence (EL) was achieved from single‐layer light‐emitting diodes of OX2‐PPV with an EL emission maximum at 555 nm and a brightness of 70 cd/m². Polymer OX2‐PPV, which was functionalized with 2,6‐bis(1,3,4‐oxadiazole‐2‐yl)pyridine, demonstrated sensitivity to various metal ions as a fluorescence‐mode chemosensor. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2112–2123, 2004     

Synthesis and optical properties of a poly(p‐phenylenevinylene) derivative and polyfluorenes with bipolar groups along the main chain

A poly(p‐phenylenevinylene) derivative (PPV–TPA)] and a series of statistical copolyfluorenes (PF–TPA)] containing oxadiazole and triphenylamine segments along the main chain were synthesized by the Heck reaction and nickel‐mediated coupling, respectively. The PF–TPA copolyfluorenes with relatively low contents of oxadiazole and triphenylamine units were readily soluble in common organic solvents, whereas the other copolyfluorenes displayed lower solubility. PPV–TPA showed excellent solubility in solvents such as tetrahydrofuran (THF), dichloromethane, chloroform, and toluene. Thin films of the polymers absorbed light in the range of 375–396 nm and had optical band gaps of 2.76–2.98 eV. They emitted blue‐green light with a maximum at 414–522 nm. The fluorescence quantum yields in THF solutions were 0.08–0.53. The copolyfluorene PF–TPA thin films with high contents of oxadiazole and triphenylamine moieties emitted pure blue light that remained stable even after annealing at 150 °C for 4 h in air. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3556–3566, 2006     

Enhancement of color purity in blue light emitting poly(fluorene)s and poly(p‐phenylene)s with 2,6‐distyrylpyridine kinked segments along the backbone

2,6‐bis(4‐Distyrylpyridine) ( 1 ) was synthesized by the condensation of 2,6‐dimethylpyridine with 4‐bromobenzaldehyde. Two new series of soluble random or alternating polyfluorenes ( PF‐Py ) and poly‐p‐phenylenes ( PP‐Py ) with various compositions were prepared by Suzuki coupling utilizing 1 as a comonomer. These polymers showed optical band gaps of 3.00–3.07 eV and photoluminescence (PL) quantum yields in solution of 0.37–0.91 for PF‐Py and 0.29–0.38 for PP‐Py . Polymers PF‐Py emitted blue light with PL maximum at 410–424 nm in solution and 406–428 nm in thin films that was red shifted with increasing distyrylpyridine content. Polymers PP‐Py behaved as blue emitters both in solution and in solid state, with PL maximum at 416–436 nm. The optical properties of these polymers could be tuned by the reversible protonation–deprotonation process of the pyridine ring. The emitted color of the polymers in solution and thin film could be changed continuously between blue and green (PL maximum up to about 520 nm) by exposing the polymers to the acid or base environment. Thin films of PF‐Py displayed excellent color stability with a small red shift of 10 nm but without additional emission band in the long wave region of the spectrum, even after being annealed at high temperature for a long time. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4486–4495, 2005     

Polyfluorenes containing tetraphenylthiophene segments: Synthesis,photophysics, and electroluminescence

2,5‐Bis(4‐bromophenyl)‐3,4‐diphenylthiophene was synthesized from benzyl chloride and sulfur and through the subsequent bromination of the intermediate 2,3,4,5‐tetraphenylthiophene. It was condensed with 2,7‐dibromo‐9,9‐dihexylfluorene via a nickel‐mediated Yamamoto coupling reaction to afford a new series of statistical copolymers with various compositions. In addition, poly(9,9‐dihexylfluorene) (PF) was synthesized under the same conditions for comparison. All the polymers were soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, and dichloromethane. Their glass‐transition temperatures increased with an increase in the tetraphenylthiophene (TPT) content in the polymers, and they were 63–149 °C. The solutions of the polymers in THF emitted intense blue light with a photoluminescence maximum at 418–440 nm and quantum yields of 0.32–0.62. Thin films of the polymers with TPT fractions lower than 20 mol % emitted blue‐green light with two well‐resolved peaks at 445 and 520 nm and an optical band gap of about 2.85 eV. A thin film of the polymer with aTPT fraction of 50 mol % emitted pure blue light with a maximum at 419 nm and an optical band gap of 3.28 eV. An enhancement of the light‐emitting‐diode brightness by a factor of ～8 with respect to that of PF was achieved in apolymer containing 5 mol % TPT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4015–4026, 2006     

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     

Coumarin‐containing poly(fluorenediylvinylene)s: Synthesis,photophysics, and electroluminescence

Two new poly(fluorenediylvinylene)s (CV and CF) with coumarin side chains were synthesized via Heck coupling. The coumarin segments were attached to the C‐9 of fluorene through alkyl spacers. The polymers were soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. The photoluminescence (PL), electroluminescence (EL), and electrochemical behavior of these polymers were studied. CV and CF thin films exhibited broad‐band, bluish‐green and orange PL emissions, with maxima at 475 and 585 nm, respectively. These PL maxima were redshifted in comparison with those measured in THF solutions. Aggregate formation played an important role in the solid state. The aggregation was more pronounced in CF thin films than CV thin films. Both polymers oxidized and reduced irreversibly. Light‐emitting devices (LEDs) with indium tin oxide hole‐injecting and aluminum electron‐injecting electrodes were prepared and studied. The LEDs made of CV emitted green light, and the LEDs made of CF exhibited an orange EL emissions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5750–5762, 2006     

Blue light‐emitting poly(p‐phenylenevinylene) derivatives containing alternating conjugated segments and aliphatic spacers

Two new poly(p‐phenylenevinylene) derivatives were prepared by Heck coupling. They contained alternating conjugated segments on the basis of p‐distyrylbenzene and flexible nonconjugated spacers. The synthesized polymers P1 and P2 carried two m‐terphenyl of four tertbutyl pendants, respectively, per repeat unit. Both polymers were amorphous and exhibited satisfactory thermal stability. Polymer P1 displayed a limited solubility in common organic solvents, whereas P2 dissolved readily in these solvents. The glass‐transition temperature values were 128 °C for P1 and 37 °C for P2 . The polymers emitted blue or violet‐blue light with photoluminescent maxima at about 445 and 460 nm for solutions and thin films, respectively. The bulky pendants reduced their tendency to form aggregates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1091–1098, 2003     

Simple synthesis,photophysics, and electroluminescent properties of poly[2,7‐bis(4‐tert‐butylstyryl)fluorene‐9, 9‐diyl‐alt‐alkane‐α,ω‐diyl]

A simple synthetic route was used for the synthesis of a novel series of alternating copolymers based on substituted 2,7‐distyrylfluorene bridged through alkylene chains. First, 2,7‐dibromofluorene was reacted with 2 equiv of butyllithium, and this was followed by a treatment with 1 equiv of α,ω‐dibromoalkane to yield the intermediate, poly(2,7‐dibromofluorene‐9,9‐diyl‐alt‐alkane‐α,ω‐diyl). ( 1 ) Heck coupling of the latter with 1‐tert‐butyl‐4‐vinylbenzene afforded the target, poly[2,7‐bis(4‐tert‐butylstyryl)fluorene‐9,9‐diyl‐alt‐alkane‐α,ω‐diyl] ( 2 ). The two versions of 2 ( 2a and 2b which have hexane and decane, respectively, as alkane groups) were readily soluble in common organic solvents. Their glass‐transition temperature was relatively low (52 and 87 °C). An intense blue photoluminescence emission with maxima at about 408 and 409 nm was observed in tetrahydrofuran solutions, whereas thin films exhibited an orange emission with maxima at 569 and 588 nm. Very large redshifts of the photoluminescence maxima and Stokes shifts in thin films indicated strong aggregation in the solid state. Both polymers oxidized and reduced irreversibly. Single‐layer light‐emitting diodes with hole‐injecting indium tin oxide and electron‐injecting aluminum electrodes were fabricated. They emitted orange light with external electroluminescence efficiencies of 0.52 and 0.36% photon/electron, as determined in light‐emitting diodes made of 2a and 2b , with alkylenes of (CH₂)₆ and (CH₂)₁₀, respectively. An increase in the external electroluminescence efficiency up to 1.5% was reached in light‐emitting diodes made of polymer blends consisting of 2a and poly(9,9‐dihexadecylfluorene‐2,7‐diyl), which emitted blue‐white light. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 809–821, 2007.     

Novel electroluminescent cationic polyelectrolyte based on poly[(fluorene‐2,7‐diylvinylene)‐alt‐(1,4‐phenylenevinylene)] and its precursor

A novel conjugated poly[(fluorene‐2,7‐vinylene)‐alt‐(1,4‐phenylenevinylene)] derivative 2 with quaternizable tertiary amino groups was synthesized by Heck coupling of a substituted 2,7‐dibromofluorene and 1,4‐dialkoxy‐2,5‐divinylbenzene. The corresponding quaternary ammonium cationic polyelectrolyte 3 was obtained by the treatment of 2 with bromoethane. Both polymers were soluble in common organic solvents, like tetrahydrofuran, chloroform, and dichloromethane. Polymer 3 showed a limited solubility in alcohols and was insoluble in water. Photophysical and electrochemical properties of the resulting polymers were fully investigated. An intensive green photoluminescence (PL) with maxima at 550 and 545 nm was observed from thin films of 2 and 3 polymers, respectively, red‐shifted compared with the PL emission spectra measured in the solution. The electrochemical band gaps were 2.38–2.45 eV. Single‐layer and double‐layer (with poly[3,4‐(ethylenedioxy)thiophene]/poly (styrenesulfonate) (PEDOT:PSS)) light‐emitting devices (LEDs) with ITO and Al electrodes were prepared and studied. They emitted a green light and their electroluminescence (EL) spectra were similar to those of PL thin films. The external EL efficiency was determined to be 0.43 and 0.32% for ITO/PEDOT:PSS/ 2 /Al and ITO/PEDOT:PSS/ 3 /Al LEDs, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1016–1027, 2007     

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     

Synthesis and electroluminescent properties of a novel 1,3,4‐oxadiazole‐containing polymer

The new blue light polymer, poly(1′,4′‐phenylene‐1″,4″‐[2″‐(2″″‐ethylhexyloxy)]phenylene‐1‴,4‴‐phenylene‐2,5‐oxadiazolyl) (PPEPPO) was synthesized through the Suzuki reaction of diboronic acid, 2‐methoxy‐[5‐(2′‐ethylhexyl)oxy]‐1,4‐benzene diboronic acid (MEHBBA) and dibromide, 2,5‐bis(4′‐bromophenyl)‐1,3,4‐oxadiazole. This polymer was characterized with various spectroscopic methods. The solid PL spectrum of PPEPPO has a maximum peak at 444 nm corresponding to blue light. Blue LED has been fabricated using this polymer as the electroluminescent layer, ITO as the anode, and aluminum as cathode. This device emitted a blue light, with 40 V of turn‐on voltage. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3086–3091, 2000     

Synthesis and optoelectronic properties of alternating benzofuran/terfluorene copolymer with stable blue emission

The solution processable alternating benzofuran/terfluorene copolymer bearing side oxadiazole groups ( PBF‐OXD ) was synthesized and its optoelectronic properties and color stability were investigated. Electron‐deficient and stereohindered oxadiazole units were used as pendent groups to compensate for the poor electron‐transporting ability of a p‐type polymer backbone, to depress the intermolecular π‐stacking, and to improve solubility while retaining polymer blue emission. PBF‐OXD showed a glass transition at 135 °C and an onset decomposition temperature of ～345 °C. A simple EL device, with the configuration of ITO/PEDOT:PSS/ PBF‐OXD /Ba/Al, displayed a stable blue emission (λ_max = 434 nm), good color purity (full width half‐maximum = 59 nm), maximum brightness of 1400 cd/m², and a maximum luminance efficiency of 0.95 cd/A. The PL and EL spectra changed slightly on annealing and on increasing the applied voltage. These results show that the as‐synthesized copolymer PBF‐OXD had integrated respective functions of its different building blocks and exhibited good thermal and color stability with improved EL performance. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5488–5497, 2009     

New blue electroluminescent n‐type polyfluorene copolymers with a 1,3,4‐oxadiazole unit in the main chain

Novel polyfluorene copolymers alternately having an 1,3,4‐oxadiazole unit in the main chain were prepared by both one‐step and two‐step methods for polyoxadiazole synthesis. They displayed highly efficient blue photoluminescence, the properties of which were affected by the extent of conjugation and the changes in the electron density by a side chain. An electrochemical analysis of the polymers using cyclic voltammetry suggested that they could be used as electron‐transport/hole‐blocking materials as well as blue emission materials for polymer light‐emitting diodes. A simple double‐layer device consisting of poly(N‐vinylcarbazole) as a hole‐transport layer and poly[(9,9′‐didodecylfluorene‐2,7‐diyl)‐alt‐((1,4‐bis(1,3,4‐oxadiazole)‐2,5‐di(2‐ethylhexyloxy)phenylene)‐5,5′‐diyl)] as an emission layer exhibited narrow blue electroluminescence with a maximum at 430 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1058–1068, 2004     

Synthesis and electro‐optical properties of light‐emitting polymers containing oxadiazole derivatives for light‐emitting diodes applications

Two PPV‐based bipolar polymers containing 1,3,4‐oxadiazole pendant groups were synthesized via the Gilch polymerization reaction for use in light‐emitting diodes (LEDs). The resulting polymers were characterized using ¹H and ¹³C NMR, elemental analysis, DSC, and TGA. These polymers were found to be soluble in common organic solvents and are easily spin‐coated onto glass substrates, producing high optical quality thin films without defects. The electro‐optical properties of ITO/PEDOT/polymer/Al devices based on these polymers were investigated using UV‐visible, PL, and EL spectroscopy. The turn‐on voltages of the OC₁Oxa‐PPV and OC₁₀Oxa‐PPV devices were found to be 8.0 V. The maximum brightness and luminescence efficiency of the OC₁Oxa‐PPV device were found to be 544 cd/m² at 19 V and 0.15 cd/A, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1098–1110, 2008     

A novel mesogen‐jacketed liquid crystalline electroluminescent polymer with both thiophene and oxadiazole in conjugated side chain

Mesogen‐jacketed liquid crystalline polymers (MJLCPs) with both electron‐transport oxadiazole and hole‐transport thiophene in the side chain were reported for their promising electroluminescent property. Monomers of 2,5‐bis{5‐[(4‐alkoxyphenyl)‐1,3,4‐oxadiazole]thiophen‐2‐yl}styrene (M‐Cm, m is the number of the carbons in the alkoxy groups, m = 8,10) were synthesized and confirmed by ¹H‐NMR, mass spectrometry, and elemental analysis. The corresponding polymers were successfully obtained and characterized by thermal analysis, optical spectroscopy, cyclic voltammetry, electroluminescent analysis, polarized light microscopy (PLM), and wide‐angle X‐ray diffraction (WAXD). The polymers exhibited high decomposition temperatures reaching 382 °C and high T_g's reaching 184 °C. The absorption spectra indicated that both the monomers and polymers had little aggregation in film than that in solution, and the absorption spectra of the polymers showed an obvious blue‐shift compared with those of the monomers. Both the monomers and the polymers had blue‐green emission, and the photoluminescence spectra of the polymers in film suggested the formation of excimer or exciplex. The polymers showed lower HOMO energy levels and LUMO energy levels than those of the MJLCPs containing oxadiazole unit reported before. Electroluminescence study with the device configuration of ITO/PEDOT/PVK/polymer/TPBI/Ca/Ag showed maximum brightness and current efficiency of 541 cd/m² and 0.10 cd/A, which proved that the introduction of directly connected electron‐ and hole‐transport units could greatly improve the EL property of side‐chain conjugated polymers. The phase structures of the polymers were confirmed to be smectic A phase through the results of PLM and WAXD. The annealed samples emitted polarized photoluminescence at room temperature, which indicated potential utility for practical applications in display. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1502–1515, 2010     

Photophysics,electrochemical properties,and electroluminescence of poly(p‐phenylenevinylene) derivatives with 1,3,5‐triphenylbenzene or 2,4,6‐triphenylpyridine segments along the backbone

The steady‐state and time‐resolved photoluminescence (PL), electrochemical behavior, and electroluminescence (EL) of didodecyloxy poly(p‐phenylenevinylene)‐based polymers that contained along the backbone structure 1,3,5‐triphenylbenzene (PC) or 2,4,6‐triphenylpyridine (PN) were studied. An intensive green PL broad‐band emission with maxima at 516 and 527 nm was observed from thin films of PC and PN polymers, respectively, redshifted in comparison with the PL emission spectra measured in tetrahydrofuran solutions. The PL decay dynamics revealed the existence of more than one excited species, and the decay curves were best described by three‐term exponential functions with a dominant lifetime of about 1 ns. The results of time‐resolved PL and steady‐state PL studies indicated excimer or aggregate formation. Both polymers oxidized irreversibly. A quasireversible reduction was observed in the PN polymer, whereas the PC polymer reduced irreversibly. For PC, slightly higher values of the ionization potential (E_IP) and electron affinity (E_A) were found (E_IP = 5.52 eV, E_A = 2.85 eV) than those for PN (E_IP = 5.37 eV, E_A = 2.77 eV). Light‐emitting devices with indium tin oxide hole‐injecting and aluminum electron‐injecting electrodes were prepared and studied. They emitted green light, and their EL spectra were similar to those of PL thin films. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 524–533, 2006     

New highly luminescent cationic polyelectrolytes based on poly(phenylenevinylene‐alt‐fluorenevinylene) or poly(fluorenevinylene) derivatives and their neutral precursors

Poly(phenylenevinylene‐alt‐fluorenevinylene) ( PF ) or poly(fluorenevinylene) ( F ) derivatives that carried alkyl chains with terminal tertiary amino groups were successfully synthesized via Heck coupling. They were postquaternized by reacting with bromoethane to the corresponding cationic polyelectrolytes PFQ and FQ . The neutral polymers PF and F as well as the quaternized polymer FQ were soluble in common organic solvents such as THF, chloroform, dichloromethane, and toluene. In contrast, the quaternized polymer PFQ did not dissolve in these solvents but was soluble in environmentally friendlier solvents like water and alcohols. The neutral precursors exhibited higher thermal stability and glass‐transition temperatures than the corresponding quaternized counterparts. All polymers emitted intense blue‐greenish light in solution (462–489 nm) with relatively high photoluminescence (PL) quantum yields 0.32–0.57, and as thin films (475–557 nm) with optical band gaps of 2.48–2.57 eV. The water soluble PFQ could find potential applications as chemo or biosensor. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1481–1491, 2007