Wittig Polycondensation Research Articles

Synthesis and light-emitting properties of a hyperbranched conjugated poly(phenylene vinylene)

A new alkoxy substituted phenyl-containing hyperbranched conjugated poly(phenylene vinylene) (Hyper-PMEH-PPV) has been synthesized through the well-known Wittig polycondensation reaction. The synthesized Hyper-PMEH-PPV was completely soluble in common organic solvents and exhibited good thermal stability up to 383 °C. The photophysical properties of Hyper-PMEH-PPV are investigated and compared with a linear conjugated poly(para-phenylene vinylene) (Linear-PMEH-PPV) and well-known MEH-PPV. An absorption maximum of Hyper-PMEH-PPV film was determined at 395 nm which was far blue-shifted than that of Linear-PMEH-PPV (428 nm). Hyper-PMEH-PPV film showed green photoluminescence (PL) peak at 513 nm. In addition, Hyper-PMEH-PPV film exhibited almost no excimer or aggregate emission peaks even when the polymer film was annealed at 80 °C for 30 min in air condition. No undesirable emissions from Hyper-PMEH-PPV film are due to the inhibition of intermolecular interaction by the introduction of the hyperbranched network into the poly(phenylene vinylene) backbone.

Synthesis and Photophysical Properties of a Hyperbranched Trimethylsilyl Substituted Poly(phenylene vinylene) Derivative

A novel trimethylsilyl substituted hyperbranched conjugated poly(phenylene vinylene) (Hyper-PBTMS-PPV) was synthesized through the Wittig polycondensation polymerization. Hyper-PBTMSPPV has good solubility in common organic solvents and showed good thermal stability up to 402 °C with less than 5 wt% weight loss. The photophysical properties of Hyper-PBTMS-PPV film are investigated and compared with trimethylsilyl-containing linear poly(1,4-phenylene vinylene) (Linear-PBTMS-PPV). An absorption maximum of Hyper-PBTMS-PPV film was determined at 335 nm which was far blue-shifted than that of Linear-PBTMS-PPV (380 nm). Hyper-PBTMS-PPV film showed blue photoluminescence (PL) peak at 449 nm. In addition, Hyper-PBTMS-PPV film exhibited almost no long wavelength emission peaks even the film was annealed at 120 °C for 30 min in air condition. High PL efficiency (Φfilm = 0.80) and no aggregate or excimer emission of Hyper-PBTMS-PPV film are due to the inhibition of intramolecular or intermolecular interaction by the introduction of the hyperbranched network into the trimethylsilyl-containing poly(phenylene vinylene) backbone.

Synthesis and light-emitting properties of a carbazole-containing hyperbranched conjugated poly(phenylene vinylene)

A new carbazole-containing hyperbranched conjugated poly(phenylene vinylene) (Hyper-PCPPV) was synthesized through the Wittig polycondensation polymerization. Hyper-PCPPV has good solubility in common organic solvents and showed excellent thermal stability up to 425 °C with less than 5% weight loss. The photophysical properties of Hyper-PCPPV were investigated and compared with a carbazole-containing linear conjugated poly(para-phenylene vinylene) (Linear-PCPPV). An absorption maximum of Hyper-PCPPV film was determined at 353 nm which was far blue shifted than that of Linear-PCPPV (403 nm). Hyper-PCPPV showed blue photoluminescence (PL) peak at 448 nm. In addition, Hyper-PCPPV exhibited almost no excimer or aggregate emission peaks even when the polymer film was annealed at 80 °C for 30 min in air condition.

Synthesis and Blue Light Emitting Properties of Meta- and Para-Linked Hyperbranched Polymers Containing Oxadiazole Unit.

Two meta-and para-linked hyperbranched polymers containing oxadiazole unit (end-capped by carbazole unit) (E-Hyper-MOXPPV and E-Hyper POXPPV) were synthesized through the Wittig poly-condensation polymerization. Both polymers showed excellent solubility in common organic solvents and exhibited good thermal stability up to 350 °C. An absorption maximum of E-Hyper-MOXPPV film was determined at 298 nm which was far blue shifted than that of E-Hyper-POXPPV film (349 nm). Light emitting properties of E-Hyper-MOXPPV and E-Hyper-POXPPV in solution and net solid film are investigated and compared each other. E-Hyper-MOXPPV and E-Hyper-POXPPV films showed blue photoluminescence (PL) peaks at 451 nm and 478 nm, respectively. Both polymers exhibited almost no excimer or aggregate emission even the films were annealed at 80 °C for 1 hr in air condition. No aggregate and excimer emission are due to inhibition of intramolecular or intermolecular interaction by the introduction of hyperbranched network into the meta-and para-linked oxadiazole containing poly(phenylene vinylene) backbone.

Synthesis and study of morphological, optical and electrical properties of new organic semi conducting polymers containing isosorbide pendant group

Tow isosorbide containing poly(phenylene vinylene-arylene vinylene)s have been synthesized via Wittig polycondensation: PPVIs-Carb (arylene: carbazole) and PPVIs-Naph (arylene: naphtalene). The macromolecular structures were characterized by NMR and FTIR spectroscopies. The polymers are soluble in common organic solvents and show good film-forming abilities thanks to the presence of the polar isosorbide side groups. These organic materials showed an amorphous behavior. A higher polarity of the surface was obtained for PPVIs-Naph. The both polymer films are photoluminescent and exhibit an optical gap of 2.3eV. The carbazole-based polymer emits in yellow-green while a green-yellow emission was obtained in the naphtalene conatainig polymer with higher fluorescence quantum efficiency. The HOMO/LUMO energy levels were determined by cyclic voltammetry and showed higher ionization potential and electronic affinity for PPVIs-Carb. The study of the ITO/polymer thin film/Al devices showed a space-charge limited current transport mechanism with charge carrier mobility in order of 10−8cm2V−1s−1.

Synthesis and light-emitting properties of a fluorene containing hyperbranched conjugated poly(phenylene vinylene)

ABSTRACTA novel fluorene containing hyperbranched conjugated poly(phenylene vinylene) (Hyper-PFPPV) was obtained through the Wittig polycondensation polymerization. Hyper-PFPPV has good solubility in common organic solvents and showed good thermal stability up to 369°C with less than 5wt% weight loss. The photophysical properties of Hyper-PFPPV in solution and net solid film are inspected and compared with fluorene containing linear poly(1,4-phenylene vinylene) (PFPPV). An absorption maximum of Hyper-PFPPV film was determined at 385 nm which was far blue shifted than that of linear PFPPV film (425 nm). Hyper-PFPPV showed blue photoluminescence (PL) peak at 461 nm. In addition, Hyper-PFPPV film exhibited almost no long wavelength emission peaks even the film was annealed at 80°C for 1 hr in air condition. High PL efficiencies (Φsol = 0.78 and Φfilm = 0.75) and no aggregate or excimer emission of Hyper-PFPPV are due to the inhibition of intramolecular or intermolecular interaction by the introduction of the hyperbranched network into the fluorene containing poly(phenylene vinylene) backbone.

Synthesis, characterization, optical and electrical properties of bis(phenylvinyl)anthracene-based polymers

A series of bis(phenylvinyl)anthracene-based polymers containing different lengths of polar ethylene glycol groups in the main chain (P1–3) were efficiently synthesized by Wittig polycondensation. These polymers are fully soluble in volatile solvents, which helped a lot to obtain high quality films. Moreover, these semi-conducting materials exhibited semi-crystalline morphology with relatively high glass transition temperature. In this article, the UV–visible absorption and fluorescence properties of P1–3 were studied consequently both in solution and as thin solid film: tan absorption-onset at 433 nm was observed and all these bis(phenylvinyl)anthracene-based polymers (P1–3) show a blue emission in solution, fluorescence quantum efficiencies being respectively 52% for P1, 75% for P2 and 67% for P3. In addition, the HOMO/LUMO energy levels were evaluated by cyclic voltammetry measurements and indicate a p-type semi-conducting materials. Finally, the electrical properties of P1–3 were investigated by recording current-tension characteristics and these experimental results were modeled by the current space-charge-limited (SCLC) mechanism.

Synthesis and self-assembly of fluorene-vinylene alternating copolymers in “Hairy-Rod” architecture: side chain – mediated tuning of conformation, microstructure and photophysical properties

In the present work, we demonstrate that the side chain choice, as a tunable parameter, is an effective strategy to drive molecular ordering, packing motifs and overall microstructure of a conjugated polymer. By applying Wittig polycondensation novel ‘rod-coil’ structures, in ‘hairy-rod’ architecture, based on fluorenylene vinylene copolymers with well-defined oligomeric side chains were synthesized using ‘T’-shaped or ‘Cross’-shaped p-terphenyl macromonomers. The overall character of the copolymers was systematically varied by attaching of hydrophilic PEG 2000, hydrophobic polar oligo-ε-caprolactone or hydrophobic and non-polar oligostyrene side chains. Self-assembling of the copolymers by simple direct dissolution method was achieved in various solvents by modifying their selectivity in relation to the side chain or main chain. The morphology investigations demonstrated that unique nanofeatures obtained in each case (helical foldamers, vesicles, disks, or helical turns) depend on the nature, number, and position of the side chains which influence the photophysical properties. The ‘hairy-rod’ topology is also responsible for the self-assembly of the materials in molten state, as thermal analysis revealed, and the propensity of the new synthesized conjugated main chain for helical folding was evidenced, as well.

Phenylethynylene-substituted poly(triphenylamine vinylene): Post-modification synthesis and (spectro)electrochemical properties

Phenylethynylene-substituted poly(triphenylamine vinylene) were synthesised in two steps by Wittig polycondensation reaction between 4,4'-diformyl-triphenylamine and bis(4-formyl phenyl)-N,N'-iodo-phenylamine in the presence of a phosphonium salt. The iodine-substituted poly(triphenylamine vinylene) were subsequently subjected to coupling reactions with phenylacetylene obtaining conjugated new structures and properties. The structures were confirmed by C13 and 1H nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) spectroscopy. The attachment of phenylethynyl substituent to the backbone of the polymers influences the optical and electrochemical properties which were analysed by ultraviolet-visible (UV-Vis) and fluorescence spectroscopy. Having triphenylamine units along the backbone, the obtained polymers exhibit electrochemical activity and their redox characteristics were investigated by running cyclic voltammetry for polymer films deposited on working electrode surface. The electrochemical data were used to estimate their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels and the band gap energy values (Eg). The polymers films change their colour while the potential is swept on the positive anodic domain, and this may be due to various oxidation states that undergo the polymers. The in situ UV-Vis vs. applied potential spectra were also recorded.

New anthracene-based semi-conducting polymer analogue of poly(phenylene sulfide): Synthesis and photophysical properties

A new anthracene-based polymer analogue of poly(phenylene sulfide) has been synthesized via Wittig polycondensation. The polymer is soluble and shows a good film quality. This organic material showed an amorphous behavior with a Tg of 70°C. The absorption and fluorescence properties of the polymer were investigated. The HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. The PAnS thin film exhibits an optical gap of 2.56eV and emits in orange region. The fluorescence quantum efficiency in dilute solution of PAnS was of 66%. A PAnS-based single-layer diode has been fabricated and shows relatively low turn-on voltage of 4.8V.

New Semiconducting Poly(arylene sulfide)s: Synthesis, Characterization, and Optical Properties

New semiconducting soluble poly(arylene sulfide)s were synthesized by Wittig polycondensation. The arylene moieties consist of distyrylbiphenyl (P1) and distyrylbithiophene (P2) π-conjugated systems. The polymers are fully amorphous and show good thermal stability. The absorption and photoluminescence properties of the polymers were investigated. P1 film has an optical gap of 2.95 eV and exhibits green-blue fluorescence. P2 shows a longer effective conjugation length with a gap of 2.42 eV and emits in the orange region. The HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. Single-layer diodes were fabricated and show relatively low turn-on voltages.

Systematic Approaches for Blue Light-emitting Polymers by Introducing Various Naphthalene Linkages into Carbazole Containing PPV Derivatives

Poly(2,3-naphthalenevinylene-alt-N-ethylhexyl-3,6-carbazolevinylene), 2,3-PNCPV, poly(2,6-naphthalene vinylenealt- N-ethylhexyl-3,6-carbazolevinylene), 2,6-PNCPV, and poly(1,4-naphthalenevinylene-alt-N-ethylhexyl-3,6- carbazolevinylene), 1,4-PNCPV were synthesized through the Wittig polycondensation reaction. The conjugation lengths of the polymers were controlled by differently linked naphthalenes in the polymer main chain. The resulting polymers were completely soluble in common organic solvents, and exhibited good thermal stability at up to <TEX>$400^{\circ}C$</TEX>. The synthesized polymers showed UV-visible absorbance and photoluminescence (PL) in the ranges of 357-374 nm and 487-538 nm, respectively. The carbazole and 2,3-linked naphthalene containing 2,3-PNCPV showed a blue PL peak at 487 nm. A single-layer light-emitting diode was fabricated with an ITO/polymer/Al configuration. The electroluminescence (EL) emission of 2,3-PNCPV was shown at 483 nm.

Linear and hyperbranched triphenylamine-based polyarylenevinylenes: a comparative optoelectronic study

The synthesis of triphenylamine-based polyarylenevinylene with linear and hyperbranched architecture is described. The synthetic route is based on Wittig polycondensation reaction at room temperature using as partners di- or tri-aldehyde of triphenylamine and bis- or tris-phosphonium salts. The polymers are separated as two fractions, one insoluble in chloroform and another one soluble in chloroform and insoluble in methanol. All polymers are obtained mostly in cis configuration, but cis linear polymers are thermally isomerized to corresponding trans structures, while branched structures are more thermally stable and isomerization process was not clearly evidenced. Characterization of the polymers was performed using NMR and FT-IR spectroscopy and thermal gravimetric analysis, while the optoelectronic properties were studied by UV–Vis and fluorescence and cyclic voltammetry, and compared with model compounds.

New anthracene-based soluble polymers: optical and charge carrier transport properties

A series of anthracene-based polymers (P1–3) have been synthesized via the Wittig polycondensation. These organic materials were soluble in common organic solvents and show good film-forming abilities. Their macromolecular structures were characterized by NMR, FT-IR spectroscopies and steric exclusion chromatography, their thermal behaviors were analyzed by differential scanning calorimetry and their HOMO-LUMO energy levels were estimated by cyclic voltammetry. The optical properties of these π-conjugated systems were investigated by UV-visible absorption and photoluminescence spectroscopies. The effect of the spacer-group structure on the photo-physical behavior, π-π stacking ability and charge carrier transport properties of the polymer has been studied.

Synthesis and study of optical properties of linear and hyperbranched conjugated polymers containing thiophene and triphenylamine units

We report the synthesis of solution processable donor–acceptor type conjugated monomer (M1) and polymers (P1 and P2) consisting of electron-accepting 1,3,4-oxadiazole unit and electron-donating 3,4-didecyloxythiophene, and triphenylamine units through Wittig polycondensation reaction. The linear polymer P1 is thermally stable up to 325 °C whereas the hyperbranched polymer P2 showed better thermal stability with an onset of decomposition at 375 °C. Polymer P2 showed lower band gap energy (1.96 eV) than that of P1 (2.09 eV). Polymers P1 and P2 emit yellow and orange light, respectively, under the irradiation of UV light. Electrochemical studies revealed that the polymers possess high-lying highest occupied molecular orbital and low-lying lowest unoccupied molecular orbital energy levels. Polymer light-emitting diodes are fabricated with the device configuration of ITO/PEDOT:PSS/polymer (P1 or P2)/Al. The device based on P2 showed a very low threshold voltage of 2 V. The third-order nonlinear optical properties of the polymers are studied using Z-scan technique. Both polymers showed a strong optical limiting behavior. The value of nonlinear absorption coefficient (β) of the polymers is of the order 10−10 mW−1 which indicates that these materials may be accomplished for fabricating optical limiters.

Highly Fluorescent Conjugated Polyelectrolyte Nanostructures: Synthesis, Self‐Assembly, and Al3+ Ion Sensing

AbstractA highly fluorescent triazine‐bridged polymer, poly[(diphenylamino‐s‐triazine)‐co‐(2‐methoxy‐5‐propyloxysulfonate‐1,4‐phenylene vinylene)] (DTMSPV), is synthesized from Wittig polycondensation of a triazine monomer with a water‐soluble p‐phenylene vinylene monomer. The fluorescent amphiphilic polymer in aqueous solution self‐assembled into nanoassemblies of micelle‐like nanostructure (MS) and π stacking nanostructure (πS), which have average sizes of 93 to 270 nm, depending on the concentration of DTMSPV. The micelle‐like nanostructure of DTMSPV (MS) shows blue emission at 457 and 488 nm with a high emission quantum yield (ΦE) of 31% in aqueous solution. On the other hand, the ΦE of π stacking structures (πS), formed in a highly concentrated solution, is lower than the MS. The MS exhibits fluorescence quenching as well as color change from blue to green/yellow, depending on the kinds of metal ions. The metal ion sensitivity is larger in the order of the main group ions (Na+, K+) &lt; dicationic transition metal ions (Zn2+, Cd2+, Pb2+, Cu2+, Pd2+) &lt; trivalent transition metal ions (Fe3+, Ru3+), with an exception of Al3+. In particular, the fluorescence of MS is dramatically quenched with color change to yellow in response to Al3+ concentrations. The selectivity and sensitivity of MS to Al3+ are unusually high even in the presence of competitive metal ions, which can be attributed to the specific interaction of triazine units with Al3+.

Blue-luminescent poly( p-phenylenevinylene) derivatives: Synthesis and effect of side-group size on the optical properties

New conjugated polymers based on separated PPV-type chromophores and incorporating different types of solubilizing side-groups (ethoxy: P1, hexyloxy: P2, dodecyloxy: P3 and benzyloxy: P4) were synthesized via Wittig polycondensation, using a series of bisphenol A-derived di(triphenylphosphonium) salts as starting monomers. The polymers are soluble in common organic solvents and their structures were confirmed by 1H NMR, 13C NMR and FTIR spectroscopies. The optical properties of these materials were investigated by UV–vis absorption and fluorescence spectroscopies. In dilute solution, quasi-identical fluorescence spectra were obtained and all the polymers showed a blue emission (420, 445 nm) and a narrow spectrum. In thin solid films, the polymers show side-group-dependent optical behavior and, whereas the emission remains blue in the case of P2, P3 and P4, a green fluorescence was observed for the ethoxylated polymer P1. From cyclic voltammetry analysis, the electrochemical band gaps were estimated to be 2.99, 3.07, 3.15 and 3.06 eV for P1, P2, P3 and P4, respectively. Single-layer diode devices of the [indium tin oxide/polymer/aluminum] configuration have been fabricated and show relatively low turn-on voltages between 2.6 and 4.9 V.

Syntheses and Characterization of 4-Octyloxybenzyl Substituted Diketopyrrolopyrrole-based Red Emitting Copolymers with Low Turn-on Voltage

Two novel diketopyrrolopyrrole-based alternating copolymers, poly(2,7-(9,9-diethyl)-fluorenylvinylene-alt-2,5-bis(4′-octyloxyphe- nylmethyl)-3,6-bis(4-vinylenephenyl)pyrrolo[3,4-c]pyrrole-1,4-dione) (P1) and poly(1,4-(2,5-dioctyl- oxy)-phenylenevinylene-alt-2,5-bis(4′-octyloxyphenylmethyl)-3,6-bis(4-vinylenephenyl)pyrrolo[3,4-c]pyrrole-1,4-dione) (P2) were synthesized through Wittig polycondensation in good yields. P1 and P2 were characterized by NMR, FT-IR, UV-Vis, photoluminescence (PL) and electroluminescence (EL). EL devices with ITO/PEDOT/polymer/CsF/Al exhibited red-emitting light with the maximum EL wavelength at 620 nm and 682 nm. The results show that PL quantum yield of the polymers in thin film can be improved through N-alkylation of diketopyrrolopyrrole (DPP) with bulky substituent. EL performance of P2 was better than P1, which might be due to 1,4-dioctyloxybenzene of P2 enhancing the hole-transporting to make more charge balance. EL devices of P1 and P2 possessed low turn on voltage (2.4 V and 2.1 V, respectively), which was an advantage for PLED.

Synthesis and spectroscopic characterization studies of low molecular weight light emitting PPV segmented copolymers

New tuneable segmented alternating copoly( p-phenylene vinylene) (PPV) derivatives were chemically synthesised via the Wittig polycondensation reaction. The chemical and optical properties in solution and in solid state were evaluated. The absorption and photoemission spectra show that incorporating an ethane dioxy spacer limits the conjugation length and produces a blue emitting copolymer, poly[1,2-ethane dioxy 2-methoxy-1,4-phenylene-vinyl 1,4-phenylene-vinyl 3-methoxy 1,4-phenylene] (EDO-PPV- 1) 1. A red shift in the copolymer emission was achieved by adding an electron-donating group, a hexoloxy-substituted PPV segment, poly[1,2-ethane dioxy 2-methoxy-1,4-phenylene-vinyl 2,5-dihexoloxy 1,4-phenylene-vinyl 3-methoxy 1,4-phenylene] (EDO-PPV- 2) 2. The photophysical properties of these block copolymers was compared with the fully conjugated copolymer poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) 3. The absorption band of the π deloc– π deloc ∗ transition at 400–500 nm is limited in 1 and 2 indicating that the conjugation is effectively interrupted. The effect of torsional motions on the Stokes shift in these segmented copolymers is discussed. The photoluminescence (PL) efficiency and lifetime of 1 and 2 is different, indicating that the contribution from additional non-radiative decay channels due to interchain interactions is significant. The steady state and time-resolved photophysical characteristics of the thin film form of the copolymers indicates a high order of stacking in copolymer 1 and strong interchain interaction leading to strong excimer emission which may be ascribed to the low folding degree and planarity of the copolymers chemical structure. The spectroscopic time-resolved analysis confirms the interchain interaction.

하이퍼브랜치 PPV를 이용한 유기 EL 소자의 제작

Hyperbranched conjugated polymers (p-HPPV and m-HPPV) with para and meta linkages were synthesized from and type monomers through Wittig polycondensation. The synthesized p-HPPV and m-HPPV were completely soluble in common organic solvents such as chloroform, tetrahydrofuran, 1,2-dichloroethane, etc. and thermal gravimetric analyses showed that p-HPPV and m-HPPV are stable up to . The molecular weights (from GPC), UV-visible, and photoluminescence maximum peaks of p-HPPV and m-HPPV are characterized in detail. The fabricated EL devices using the synthesized hyperbranched polymers, (ITO/(p-HPPV or m-HPPV)/Al), showed EL emission at about 507 nm and 481 nm (681 nm), respectively. Especially, EL device from m-HPPV were found to exhibit nearly white emission with approximate CIE coordinates of (0.31, 0.34) compared with (0.310, 0.316) of NTSC white color at . The good photophysical properties combine with good film-form ability could make these hyperbranched polymers to be a potential candidate for the EL materials.