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Synthesis of n-type organic semiconductors with high electron mobilities, good environmental stability, and good processability is an urgent task in current organic electronics. This is because most of π-conjugated materials are p-type and prefer to transport positive hole carriers. In this article, a series of new dicarboxylic imide-substituted poly(p-phenylene vinylenes) (DI-PPVs) were first synthesized. They exhibited a high electron affinity of 3.60 eV and thus are able to transport electrons. The polymers showed tunable solubility in common organic solvents and high chemical and thermal stability. They remain rigidity of the PPV backbone, and strong interchain π-stacking was observed in thin films by X-ray diffraction measurement. All these suggested that these polymers could serve as good candidates as n-type semiconductors in organic electronic devices such as n-channel field-effect transistors and all polymer-based solar cells.

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 H 1 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.

Two new poly(phenylene vinylene)s (PPVs) carrying electron-donating triphenylamine or carbazole and electron-deficient quinoxaline units were synthesized and characterized. Their properties were compared with those of PPV containing only quinoxaline unit. The two polymers showed PL maximum at 501–510 in solution and 533–540 in thin film. Because of the presence of electron donor and acceptor units they displayed strong intramolecular charge transfer (ICT) effects; hence, low-photoluminescence quantum yields. The polymers showed reversible electrochemical reduction with electron affinity of 2.75 eV and irreversible oxidation with ionization potential of 5.10–5.24 eV. Single-layer LED of configuration ITO/PEDOT/polymer/Al showed low turn-on voltage at 5 V, but limited brightness of 50–60 cdm−2. The electroluminescence maximum was voltage-tunable varying from 500 to 542 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2367–2378, 2008

Three series of poly(phenylene vinylene) (PPV) derivatives containing hole-transporting triphenylamine derivatives [N-(4-octoxylphenyl)diphenylamine, N,N'-di(4-octyloxylphenyl)-N,N'-diphenyl-1,4-phenylenediamine, and N,N'-di(4-octoxylphenyl)-N,N'-diphenylbenzidine] (donor) and electron-transporting oxadiazole unit (2,5-diphenyl-1,3,4-oxadiazole) (acceptor) in the main chain were synthesized by improved Wittig copolymerization. The resulting donor-acceptor (D-A) polymers are readily soluble in common organic solvents, such as chloroform, dichloroethane, THF, and toluene.

To study the effect of connector structure between hole- and electron-transporting segments, we synthesized and characterized new electroluminescent polymers P1–P7 consisting of hole-transporting 1,4-bis(hexyloxy)-2,5-distyrylbenzene (DSB: P1 and P2) and electron-transporting 4-(4-(hexyloxy)phenyl)-3,5-diphenyl-4H-1,2,4-triazole (TAZ: P3 and P4) or 2-(2,5-bis(hexyloxy)-4-(5-phenyl-1,3,4-oxadiazol)phenyl)-5-phenyl-1,3,4-oxadiazole (DIOXD: P5–P7) segments linked by different connectors. The connectors between hole- and electron-transporting segments are (1) 1,4-phenylene in P3 and P5, (2) 1,4-divinylbenzene in P4 and P6, and (3) 4,4′-biphenyl in P7. Three corresponding end-capped model polymers P1-M, P2-M, and P3-M were also synthesized to evaluate the effect of end groups. From optimized semiempirical MNDO calculations, the adjacent benzene rings between DSB and TAZ or DIOXD chromophores in P3, P5, and P7 twist about 81°–89°. The effect of twisted architectures and connectors in optical and electrochemical properties for P1–P7 have been discussed by comparing with copolymers P1 and P2, which possess single bond or ether spacer as connectors. From cyclic voltammograms, the torsion in P3, P5, and P7 confines electron delocalization and leads to simultaneously enhanced hole and electron affinity as compared to those of P1 and P2. Furthermore, double-layer light-emitting diodes with a configuration of ITO/PEDOT:PSS/P1–P7/Al all reveal green–yellow electroluminescence with maximum luminance at 8–320 cd/m2 and their performances are greatly influenced by the connector's structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4514–4531, 2006

Factors affecting the syntheses ofhigh-molecular-weight poly(2,5-dialkyl-1,4-phenylene vinylene) by the acyclic diene metathesis polymerization of 2,5-dialkyl-1,4-divinylbenzenes [alkyl = n-octyl (2) and 2-ethylhexyl (3)] with a molybdenum or ruthenium catalyst were explored. The polymerizations of 2 by Mo(N-2,6-Me 2 C 6 H 3 ) CHMe 2 Ph)[OCMe(CF 3 ) 2 ] 2 at 25 C was completed with both a high initial monomer concentration and reduced pressure, affording poly(p-phenylene vinylene)s with low polydispersity index values (number-average molecular weight = 3.3-3.65 x 10 3 by gel permeation chromatography vs polystyrene standards, weight-average molecular weight/number-average molecular weight = 1.1-1.2), but the polymerization of 3 was not completed under the same conditions. The synthesis of structurally regular (all-trans), defect-free, high-molecular-weight 2-ethylhexyl substituted poly(p-phenylene vinylene)s [poly3; degree of monomer repeating unit (DP n ) = ca. 16-70 by 1 H NMR] with unimodal molecular weight distributions (number-average molecular weight = 8.30-36.3 x 10 3 by gel permeation chromatography, weight-average molecular weight/number-average molecular weight = 1.6-2.1) and with defined polymer chain ends (as a vinyl group, -CH=CH 2 ) was achieved when Ru(CHPh) (Cl) 2 (IMesH 2 )(PCy 3 ) orRu(CH-2-O i Pr-C 6 H 4 )(Cl) 2 (IMesH 2 )[IMesH 2 = 1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene] was employed as a catalyst at 50 C.

A novel synthetic method for soluble precursor polymers of poly(p-phenylene vinylene) (PPV) derivatives by the palladium-catalyzed three-component coupling polycondensation of aromatic diiodides, aromatic bis(boronic acid) derivatives, and norbornadiene is described. For example, the polymerization of 1,4-diiodo-2,5-dioctyloxybenzene, benzene-1,4-bis(boronic acid propanediol ester), and norbornadiene at 100 °C for 3 days provided a polymer consisting of the three monomer units in a 97% yield (number-average molecular weight = 3100, weight-average molecular weight/number-average molecular weight = 1.37). A derivative of PPV was produced smoothly by the retro Diels–Alder reaction of the polymer both in a dodecyloxybenzene solution and in a film at 200 °C in vacuo. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3403–3410, 2005

cited By 9; International audience; Water-soluble and photoluminescent block copolymers [poly(ethylene oxide)-block-poly(p-phenylene vinylene) (PEO-b-PPV)] were synthesized, in two steps, by the addition of α-halo-α′-alkylsulfinyl-p-xylene from activated poly(ethylene oxide) (PEO) chains in tetrahydrofuran at 25°C. This copolymerization, which was derived from the Vanderzande poly(p-phenylene vinylene) (PPV) synthesis, led to partly converted PEO-b-PPV block copolymers mixed with unreacted PEO chains. The yield, length, and composition of these added sequences depended on the experimental conditions, namely, the order of reagent addition, the nature of the monomers, and the addition of an extra base. The addition of lithium tert-butoxide increased the length of the PPV precursor sequence and reduced spontaneous conversion. The conversion into PPV could be achieved in a second step by a thermal treatment. A spectral analysis of the reactive medium and the composition of the resulting polymers revealed new evidence for an anionic mechanism of the copolymerization process under our experimental conditions. Moreover, the photoluminescence yields were strongly dependant on the conjugation length and on the solvent, with a maximum (70%) in tetrahydrofuran and a minimum (

A series of new poly(p-phenylene vinylene) derivatives with different den- dritic pendants—poly{2-(3 0 ,5 0 -bis(2@-ethylhexyloxy)benzyloxy)-1,4-phenylenevinylene} (BE-PPV), poly{2-(3 0 ,5 0 -bis(3@,7@-dimethyl)octyloxy)-1,4-phenylenevinylene} (BD-PPV), poly(2-{3 0 ,5 0 -bis(3@,5@-bis(2 000 -ethylhexyloxy)benzyloxy)benzyloxy}-1,4-phenylenevinylene) (BBE-PPV), poly(2-{3 0 ,5 0 -bis(3@,5@-bis(3 000 ,7 000 -dimethyloctyloxy)benzyloxy)benzyloxy}- 1,4-phenylenevinylene) (BBD-PPV), and poly((2-{3 0 ,5 0 -bis(3@,5@-bis(2 000 -ethylhexyloxy)- benzyloxy)benzyloxy}-1,4-phenylenevinylene)-co-(2-{3 0 ,5 0 -bis(3@,5@-bis(3 000 ,7 000 -dimethyl- octyloxy)benzyloxy)benzyloxy}-1,4-phenylenevinylene)) (BBE-co-BBD-PPV; 1:1) —were successfully synthesized according to the Gilch route. The structures and properties of the monomers and the resulting conjugated polymers were character- ized with 1 H and 13 C NMR, elemental analysis, gel permeation chromatography, thermogravimetric analysis, ultraviolet-visible absorption spectroscopy, photolumi- nescence, and electroluminescence spectroscopy. The obtained polymers possessed excellent solubility in common solvents and good thermal stability, with a 5% weight loss temperature of more than 328 8C. The weight-average molecular weights and polydispersity indices of BE-PPV, BD-PPV, BBE-PPV, BBD-PPV, and BBE-co-BBD- PPV (1:1) were in the range of 1.33-2.28 � 10 5 and 1.35-1.53, respectively. Double- layer light-emitting diodes (LEDs) with the configuration of indium tin oxide/poly- mer/tris(8-hydroxyquinoline) aluminum/Mg:Ag/Ag devices were fabricated, and they emitted green-yellow light. The turn-on voltages of BE-PPV, BD-PPV, BBE-PPV, BBD-PPV, and BBE-co-BBD-PPV (1:1) were approximately 5.6, 5.9, 5.5, 5.2, and 4.8 V, respectively. The LED devices of BE-PPV and BD-PPV possessed the highest electroluminescent performance; they exhibited maximum luminance with about 860 cd/m 2 at 12.8 V and 651 cd/m 2 at 13 V, respectively. The maximum luminescence efficiency of BE-PPV and BD-PPV was in the range of 0.37-0.40 cd/A. V C 2005 Wiley

Two novel poly(p-phenylene vinylene) polymers, which carried side substituents with cyano groups or 1,3,4-oxadiazole, were synthesized by Heck coupling. They consisted of alternating conjugated segments and nonconjugated aliphatic spacers. The polymers had moderate molecular weights, were amorphous, and dissolved readily in tetrahydrofuran and halogenated organic solvents. They were stable up to approximately 340 °C in N2 and 290 °C in air, and the anaerobic char yield was around 60% at 800 °C. The polymer with cyano side groups emitted blue light in solutions and thin films with identical photoluminescence (PL) maximum at 450 nm; this supported the idea that chain interactions were hindered even in the solid state. The PL maximum of this polymer in thin films was blueshifted upon annealing at 120 °C, indicating a thermochromic effect as a result of conformational changes in the polymer backbone. The polymer containing side substituents with oxadiazole rings emitted blue light in solutions with a PL maximum at 474 nm and blue-greenish light in thin films with a PL maximum at 511 nm. The PL quantum yields of the polymers in tetrahydrofuran were 0.13–0.24. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1768–1778, 2004

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/m 2 . 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.

A poly(p-phenylenevinylene) (PPV) derivative containing a bulky (2,2-diphenylvinyl)phenyl group in the side chain, EHDVP-PPV, was synthesized by Gilch route. The reduced tolane-bisbenzyl (TBB) defects, as well as the structure of the polymer, was confirmed by various spectroscopic methods. The intramolecular energy transfer from the (2,2-diphenylvinyl)phenyl side group to the PPV backbone was studied by UV-vis and photoluminescence (PL) of the obtained polymer and model compound. The polymer film showed maximum absorption and emission peaks at 454 and 546 nm, respectively, and high PL efficiency of 57%. A yellow electroluminescence (λmax = 548 nm) was obtained with intensities of 6479 cd/m2 when the light-emitting diodes of ITO/PEDOT/EHDVP-PPV/LiF/Al were fabricated. The maximum power efficiency of the devices was 0.729 lm/W with a turn-on voltage of 3.6 V. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5636–5646, 2004

A soluble cyano-substituted poly[(1,3-phenylene vinylene)-alt-(1,4-phenylene vinylene)] derivative (9) was synthesized and characterized. Comparison between 9 and its model compound (10) showed that the chromophore in 9 remained to be well defined as a result of a π-conjugation interruption at adjacent m-phenylene units. The attachment of a cyano substituent only at the β position of the vinylene allowed the maximum electronic impact of the cyano group on the optical properties of the poly(p-phenylene vinylene) material. At a low temperature (−108 or −198 °C), the vibronic structures of 9 and 10 were partially resolved. The absorption and emission spectra of a film of 9 were less temperature-dependent than those of a film of 10, indicating that the former had a lower tendency to aggregate. A light-emitting diode (LED) based on 9 emitted yellow light (λmax ≈ 578 nm) with an external quantum efficiency of 0.03%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3149–3158, 2003

Poly[(2-alkyloxy-5-methyl-1,3-phenylenevinylene)-alt-(1,3-phenylenevinylene)]s (8) and poly[(2-alkyloxy-5-methyl-1,3-phenylenevinylene)-alt-(1,4-phenylenevinylene)]s (10) were synthesized by the Wittig reaction to provide materials containing 45–62% cis-vinylene bonds. The optical characteristics of 8 and 10 were compared with those of their respective isomers, 3 and 4, the cis-vinylene contents of which were significantly lower (9–16%). Although a greater fraction of cis-CHCH linkages caused the absorption maximum (λmax) of 8 and 10 to be slightly blueshifted (by ∼3–6 nm) from that of 3 and 4, the impact of the vinylene bond geometry appeared to be negligible on their fluorescence spectra. The fluorescence quantum efficiencies of 8 and 10 were estimated to be approximately 0.25 and 0.72, respectively. Both 8 (λmax ≈ 445 or 462 nm) and 10 (λmax ≈ 480 or 506 nm) were electroluminescent, showing effective color tuning by the controlled insertion of m-phenylene moieties. The external electroluminescence quantum efficiencies were determined to be 4.26 × 10−3% for 8 and 0.63% for 10. The cis/trans-vinylene bond ratio had a great impact on the electroluminescence device performance of 8 but a much smaller impact on the performance of 10. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 303–316, 2004

Poly(p-phenylene vinylene) (PPV), poly(2,5-dioctyl-p-phenylene vinylene) (PDOPPV), and poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEHPPV) were synthesized by a liquid-solid two-phase reaction. The liquid phase was tetrahydrofuran containing 1,4-bis(bromomethyl)benzene, 1,4-bis(chloromethyl)-2,5-dioctyl-benzene, or 1,4-bis(chloromethyl)-2-methoxyl-5-(2'-ethylhexyloxy)benzene as the monomer and a certain amount of tetrabutylammonium bromide as a phase-transfer catalyst. The solid phase consisted of potassium hydroxide particles with diameters smaller than 2 mm. The experimental results demonstrated that the reaction conversions of PPV and PDOPPV were fairly high (∼65%), but the conversion of MEHPPV was only 45%. Moreover, gelation was found in the polymerization processes. As a result, PPV was insoluble and PDOPPV and MEHPPV were partially soluble in the usual organic solvents, such as tetrahydrofuran and chloroform. Soluble PDOPPV and MEHPPV were obtained with chloromethylbenzene or bromomethylbenzene as a retardant regent. The molar mass of soluble PDOPPV was measured to be 2 x 10 4 g mol -1 , and that of MEHPPV was 6 × 10 4 g mol -1 . A thin, compact film of MEHPPV was formed via spin coating, and it emitted a yellow light.

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.

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 degreesC) and high decomposition temperature (> 300 degreesC) 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 photoluminesence 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. (C) 2001 John Wiley & Sons, Inc.

A new p-phenylene–vinylene–thiophene-based siloxane block copolymer has been synthesized. The copolymer consists of alternating rigid and flexible blocks. The rigid blocks are composed of phenylene–vinylene–thiophene-based units, and the flexible blocks are derived from 1,3-dialkyldisiloxane units. The former component acts as the chromophore, and allows fine tuning of band gap for blue-light emission, while the latter imparts good solubility of the copolymer in organic solvents, and thus, should enhance processibility of the resulting copolymer. The thermal properties of the copolymer have been characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The photoluminescence (PL) of the copolymer in solution and in cast film has been studied. The effects of concentration on the PL intensity of the new copolymer in polymer blends with poly(methyl methacrylate) (PMMA) and poly(vinyl carbazole) (PVK) have also been described. Efficient energy transfer from PVK to the new block copolymer in the blended film was observed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1450–1456, 2000