Electrochemical synthesis of conjugated polymer wires and nanotubules

Two electrochemical methods designed for the synthesis of polypyrrole (PPy) wires and nanotubules are the topic of this paper. The concept that allows the morphology of PPy to be controlled is discussed for each method, and the performances of the two complementary techniques are compared in terms of dimension, shape and conductivity of PPy.     

Synthesis and optoelectronic properties of amino-functionalized carbazole-based conjugated polymers

A series of alcohol soluble amino-functionalized carbazole-based copolymers were synthesized via Suzuki coupling reaction.The pendent amino groups endow them high solubility in polar solvents,as well as efficient electron injection capability from high work-function metals.The relationships between the photophysical and electrochemical properties and the polymer backbone structure were systematically investigated.These alcohol-soluble carbazole-based copolymers were used as cathode interlayers between the high work-function metal Al cathode and P-PPV emissive layer in polymer light-emitting diodes with device structure of ITO/PEDOT:PSS/P-PPV/interlayer/Al.The resulting devices exhibited improved performance due to the better electron injection/transporting ability of the designed copolymers from Al cathode to the light-emitting layer.     

胺基功能化咔唑共轭聚合物的合成及其光电性能研究

发展了新型含有胺基的支化烷基修饰的咔唑单元,并且与芴、咔唑、苯等单元通过Suzuki偶联反应共聚得到不同主链结构的水/醇溶共轭聚合物界面修饰材料,研究了主链结构的变化对材料光物理、电化学性能的影响.所有聚合物均被用作阴极界面材料应用于器件结构为ITO/PEDOT：PSS/P-PPV/界面层/Al的聚合物发光二极管中.在相同器件制备条件下,系统比较了不同主链结构的界面修饰材料在器件中的性能,并研究了性能差异的原因.器件研究结果表明,在高功函数金属Al阴极的聚合物发光二极管中,含胺基功能化咔唑单元的水/醇溶共轭聚合物材料由于界面偶极的形成,均表现出很好的电子注入/传输性能,与之对应的器件性能得到大幅提升.     

Aggregation structures of organic conjugated molecules on their optoelectronic properties

The intimate connection between stacking modes and optoelectronic properties of organic conjugated materials has been discussed from the viewpoints of developing microscopic models and further understanding of their functions and potential applications. In particular, three basal dimer configurations (cofacial configuration, staggered configuration, and crossed configuration) and their respective optical (including radiative and non-radiative) and electrical properties are expatiated in detail. Eventually, we put forward the perspective on achieving the promising laser material that features high fluorescence quantum yield and charge mobility.     

Size-dependent spectroscopic properties of conjugated polymer nanoparticles

This paper is focused on how the spectroscopic properties of conjugated polymers evolve in the size range between single polymer chains and the bulk material. The measurements used single-particle spectroscopy techniques and include both static and dynamic measurements. The main observation of this work is that the spectroscopic properties of MEH-PPV evolve rapidly as a function of nanoparticle size and achieve bulk-like properties for nanoparticles greater than 10 nm in size. Nanoparticles were assembled by a reprecipitation technique and characterized by fluorescence emission spectroscopy. The physical origin of the size-dependent spectroscopic properties is assigned to the distance dependence of four main processes: electronic energy transfer between blue and red sites, triplet-triplet annihilation, singlet exciton quenching by triplets, and singlet exciton quenching by hole polarons.     

Synthesis and optoelectronic properties of conjugated polymers based on a dithienobenzimidazole unit in the main chain

Three conjugated polymers with the dithienobenzimidazole (DTBIm) unit ( P1 , P3 , and P4 ) and one conjugated polymer with the dithienobenzoxazole unit ( P2 ) were synthesized by the cross‐coupling polymerization. The absorption maxima showed a red‐shift in the order of P3 (406 nm), P2 (426 nm), P1 (438 nm), and P4 (450 nm), which was studied in detail using the frontier molecular orbital calculation of the model compounds. The energy levels of the highest occupied molecular orbital and the lowest unoccupied molecular orbital of the DTBIm unit‐containing conjugated polymers were estimated by the cyclic voltammetry. The transformation from DTBIm ( P4 ) to dithienobenzimidazolium ( P4' ) was also carried out to shift the absorption maxima of P4' (454 nm) by promoting the intramolecular charge transfer between the DTBIm and thiophene units. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 401–409     

Toward design of high-performance optoelectronic materials: comparative theoretical studies on the photophysical and charge transport properties of fluorene-based compounds

As an important building block for optoelectronic applications, various chemical modifications at C9-position of fluorene have been proposed to enhance its performance by suppressing the well-known keto effect. In order to identify different substitution effects on the photophysical and charge transport properties of fluorene, we systematically study the electronic structures and photophysical behaviors of fluorene (FR) and its three dimerized counterparts, namely, 9,9′-spirobifluorene (SBF), 9,9′-bifluorenylidene (BFD), and bis(biphenyl-2-2-diyl)allene (BDA), by employing density functional theory calculations. The changes in bond length alternation indicate that the geometrical relaxations of the fluorene unit in its dimerized derivatives are smaller than FR compound. This fact was further proved by the nonradiative decay rate estimated of the first excited singlet state for each compound. Meanwhile, the vibration relaxation analyses suggest that the bridge between two fluorene fragments plays an important role in the nonradiative decay process. In addition, the injection abilities were evaluated in terms of the ionization potentials and electron affinities, and the carrier transport properties were discussed in the framework of Marcus theory. We find BFD could be a better ambipolar transport material, and BDA can be used as a high-efficient luminescent building unit with excellent hole transport property.     

Synthesis, processing and properties of conjugated polymer networks

Despite the diverse research activities focused on the chemistry, materials science and physics of conjugated polymers, the feature of conjugated cross-links, which can provide electronic communication between chains, has received little attention. This situation may be a direct consequence of the challenge to introduce such links while retaining adequate processability. Focusing on recent studies of materials for which charge transport or electrical conductivity data are available, this feature article attempts to present an overview of the synthesis, processing and electronic properties of conjugated polymer networks. For the purpose of this discussion, two distinctly separate architectures-featuring covalent cross-links on the one hand and non-covalent organometallic bridges on the other-are treated in separate sections. The available data indicate that cross-linking can have significant benefits for intermolecular charge transfer if the polymers are carefully designed.     

Influence of the surfactant chain length on the fluorescence properties of a water-soluble conjugated polymer

In this work, we report the influence of surfactant chain length and surfactant concentration on the photoluminescence (PL) of water-soluble pi-conjugated poly(thienyl ethylene oxide butyl sulfonate) (PTE-BS). We have used alkylammomium surfactants with 8, 9, 10, and 12 carbon atoms per hydrocarbon chain. The surfactant concentration was varied from 0.125 the critical micelle concentration (CMC) up to 2 times the CMC. The results show that at premicellar concentrations all the surfactants promote the polymer aggregation inducing an increase in the interchain charge transfer by pi-pi interactions, which competes with PL emission processes. However, in the premicellar range, the polymer PL emission is sharply affected by the surfactant chain length. Thus, the PL is quenched by the surfactants with the shortest tails, whereas the surfactants with the longest ones provoke an enhancement of the PL emission. This behavior has been associated with the capacity of the surfactants with the longest hydrocarbon chains to accommodate their tails inside the polymer, obstructing the appearance of pi-pi interchain interactions during aggregation and reducing intrachain defects. By contrast, at the CMC, the surfactant chain length does not modify the PL emission, since the excess of surfactant inhibits polymer aggregation, thus enhancing the efficiency of light emissive processes.     

Molecular engineering tuning optoelectronic properties of thieno[3,2-b]thiophenes-based electrochromic polymers

Thieno[3,2-b]thiophene(TT)monomers end-capped with 3,4-ethylenedioxythiophene(EDOT)moieties are electropolymerized to formπ-conjugated polymers with distinct electrochromic(EC)properties.Steric and electronic factors(electron donor and acceptor substituents)in the side groups of the TT core,as well as the structure of the polymer backbone strongly affect the electrochemical and optical properties of the polymers and their electrochromic characteristics.The studied polymers show low oxidation potentials,tunable from-0.78 to+0.30 V(vs.Fc/Fc~+)and the band gaps from 1.46 to 1.92 eV and demonstrate wide variety of color palettes in polymer films in different states,finely tunable by structural variations in the polymer backbone and the side chains.EC materials of different colors in their doped/dedoped states have been developed(violet,deep blue,light blue,green,brown,purple-red,pinkish-red,orange-red,light gray,cyan and colorless transparent).High optical contrast(up to 79%),short response time(0.57-0.80 s),good cycling stability(up to 91%at 2000 cycles)and high coloration efficiency(up to 234.6 cm2C~(-1))have been demonstrated and the influence of different factors on the above parameters of EC polymers have been discussed.     

The photophysical properties and morphology of fluorene-alt-benzene based conjugated polymer

A series of fluorene-alt-benzene based conjugated main chain polymers chemically attached with alkyl side chains of different lengths on phenylene rings were designed and synthesized by a palladium catalyzed Suzuki coupling reaction. The UV-vis absorption and fluorescence spectra, thermal stability of spectral property, phase transition behavior and morphology of the synthesized polymers were investigated. With increasing the length of the alkyl side chain, the UV and fluorescence spectra exhibit an obvious blue shift compared with those of the unsubstituted polymer. The alkyl substitution improves the thermal spectral stability of the polymers due to the steric hindrance of the alkyl side chains, thus leading to efficient separation of the main chain backbones. The phase transition behavior is closely related to the length of the alkyl side chains attached on the phenylene rings. The annealed films of the polymers display characteristic nematic liquid crystalline texture. TEM observations indicate that solvent-cast thin deposits of all the polymers show typical fibrillar morphology.     

Synthesis and magnetic properties of complexes of a conjugated hyperbranched polymer containing bithiazole rings

A novel conjugated hyperbranched polymer containing bithiazole rings（PBTADB） was synthesized by polycondensation of 1,3,5-benzenetricarboxaldehyde and 2,2’-diamino-4,4’-bithiazole（DABT）.The structure of the hyperbranched polymer was confirmed by FT-IR and ¹H-NMR.PBTADB dissolved in organic polar solvents such as DMSO and NMP.Bithiazole rings were introduced to provide bidentate N-donor sites for binding metal ions.The metal complexes were prepared by chelation of the polymer with Co²⁺ and Sm³⁺.The magnetic behavior of coordination compounds was measured as a function of magnetic field strength（0-4.8×10⁶ A/m） at 5 K and as a function of temperature（5-300 K） at magnetic field strength of 2.4×10⁶ A/m.The magnetic hysteresis loops of PBTADB-Sm³⁺and PBTADB-Co²⁺showed the typical ’S’ shape at 5 K with the Curie-Weiss temperature T_θ=96 K and 41 K respectively.The results show that they exhibit properties of soft ferromagnetic materials.     

Synthesis and optoelectronic properties of a carbazole-modified platinum(II) complex in polymer light-emitting devices

To improve opto-electronic properties and efficiently suppress excimer emission, a phenylpyridine (ppy)-based platinum(II) complex (C(16)OCz-ppy)Pt(acac) was synthesized and characterized, where C(16)OCz-ppy is a 2-phenylpyridine derivative appending a carbazole moiety and three hexadecyloxy methyl units in the parent phenylpyridine, and acac is acetylacetone. This carbazole-modified platinum(II) complex exhibited good thermal stability and three times higher photoluminescent quantum yield than its parent (2-phenylpyridine-C(2),N)(2,4-pentanedionato-O,O)platinum(II) complex [(ppy)Pt(acac)]. Single-emissive-layer polymer light-emitting devices using (C(16)OC(Z)-ppy)Pt(acac) as dopant and a blend of poly(N-vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as host matrix presented a maximum current efficiency of 1.51 cd A(-1), which was 1.5 times higher than that from the (ppy)Pt(acac)-doped device with the same device structure. Little excimer emission and minor aggregation emission were observed in the (C(16)OC(Z)-ppy)Pt(acac)-doped PLEDs at different dopant concentrations and applied voltages. This work indicates that introducing a carbazole and three hexadecyloxy methyl groups into the planar platinum(II) complex can reduce molecular aggregation and excimer emissions, thus resulting in high luminance and stable EL spectra in comparison with the parent (ppy)Pt(acac).     

Synthesis and optical and electrochemical properties of a bispyrimidinium-dibenzothiophene-S,S-dioxide-based cationic conjugated polymer

A novel n-type cationic conjugated polymer (PFSOmiCl), consisting of bispyrimidinium-dibenzothiophene-S,S-dioxide and fluorene scaffolds, was developed from its polymeric precursor (PFSOmi) through an intramolecular cyclization reaction. In comparison with PFSOmi, PFSOmiCl exhibits significant bathochromical absorption and photoluminescence spectra in both solution and film form, as well as a more hydrophilic film surface. Cyclic voltammetry tests demonstrate that PFSOmiCl possesses a deep lowest unoccupied molecular orbital (LUMO) energy level of ?4.18 eV, which is comparable to the LUMO energy levels of common fullerene derivatives. These unique properties endow PFSOmiCl with great utilization potential in organic optoelectronic devices. Moreover, this research offers a novel guideline for designing new conjugated polyelectrolytes.     

Broadband optical limiting and nonlinear optical absorption properties of a novel hyperbranched conjugated polymer

The nonlinear transmittance of a novel hyperbranched conjugated polymer named DMA-HPV has been measured in CHCl₃ solution using a nanosecond optical parametric oscillator. DMA-HPV shows excellent optical limiting performance in the visible region from 490 to 610 nm. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its huge and broadband nonlinear optical absorption.     

Modulation of the electronic properties of conjugated polymers through design of polymer backbone

We present the results of valence effective hamiltonian (VEH) band structure calculations on stereoregular block copolymers of poly(thienylene vinylene) and poly(pyrrylene vinylene). We have examined the evolution of the electronic properties as a function of the extension and distribution of the block copolymer sequences. In both cases, the electronic-properties deviate from a linear evolution as a consequence of the localization of both HOCO and LUCO.     

Enhanced dispersion stability of supramolecular complexes of single-walled carbon nanotubes with fluorene-based conjugated polymers

Supramolecular complexes of single-walled carbon nanotubes (SWNTs) with poly(9,9-didodecylfluorene-2,7-diyl) (PF) derivatives were prepared using a solution dispersion process. A series of novel conjugated PF polymers with carboxyl or hydroxyl end groups at both ends were synthesized by the Yamamoto-type coupling of 2,7-dibromo-9,9-didodecylfluorene using Ni(COD)₂ as a catalyst, and further end-capped with either 4-bromobenzoic acid or 4-bromobenzyl alcohol to obtain the end-functionalized PF with different terminal groups. An α-monocarboxy-ω-mono-methoxy poly(ethylene glycol) was connected to both ends of the PF-containing hydroxyl end groups to produce triblock copolymers of poly(ethylene glycol)-b-polyfluorene-b-poly(ethylene glycol) (PEO-b-PF-b-PEO). These SWNTs were completely wrapped with the conjugated polymers through π–π interactions, which enhanced the solubility of the SWNT complexes in organic media, and prevented the aggregation of the polymer–SWNT complexes into large bundles. This indicates that the dispersion stability of SWNTs is enhanced by the addition of the conjugated polymers.     

Incorporation of different conjugated linkers into low band gap polymers based on 5,6‐Bis(octyloxy)‐2,1,3 benzooxadiazole for tuning optoelectronic properties

Four new 2,1,3‐benzooxadiazole‐based donor–acceptor conjugated polymers, namely poly{9‐(9‐heptadecanyl)‐9H‐carbazole‐alt‐5,6‐bis(octyloxy)‐4,7‐di(selenophen‐2‐yl)benzo[c][1,2,5]oxadiazole)}(PSBSC), poly{9‐(9‐heptadecanyl)‐9H‐carbazole‐alt‐5,6‐bis(octyloxy)‐4,7‐di(furan‐2‐yl)benzo[c][1,2,5]oxadiazole)}(PFBFC), poly{9,9‐dioctyl‐9H‐fluorene‐alt‐5,6‐bis(octyloxy)‐4,7‐di(selenophen‐2‐yl)benzo[c][1,2,5]oxadiazole)}(PSBSFL), and poly{9,9‐dioctyl‐9H‐fluorene‐alt‐5,6‐bis(octyloxy)‐4,7‐di(furan‐2‐yl)benzo[c][1,2,5]oxadiazole)}(PFBFFL), were synthesized via Stille polycondensation reaction. All polymers were found to be soluble in common organic solvents such as chloroform, tetrahydrofuran, and chlorobenzene. Their structures were verified by ¹H‐NMR and the molecular weights were determined by gel permeation chromatography (GPC). The polymer films exhibited broad absorption bands. Among all polymers, photovoltaic cells based on the device structure of ITO/PEDOT:PSS/PSBSC:PC₇₁BM(1:3, w/w)/LiF/Al revealed an open‐circuit voltage of 0.62 V, a short circuit current of 7.63 mA cm^?2 and a power conversion efficiency of 1.89%. This work demonstrates a good example for tuning absorption range, energy level, and photovoltaic properties of the polymers with different spacers and donor units can offer a simple and effective method to improve the efficiency of PSCs. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2459–2467     

Synthesis of a novel highly conjugated conducting polymer

The new conjugated polyacetylene derivative dehydrated poly(4-hydroxy-4-phenyl-1-butyne) [dehydrated poly(HPB)] was synthesized from poly(4-hydroxy-4-phenyl-1-butyne) [poly(HPB)], which was obtained by the polymerization of 4-hydroxy-4-phenyl-1-butyne. The resulting dehydrated poly(HPB) was soluble in common organic solvents. The dehydrated poly(HPB) was found to have extended conjugated polyene structure. The dehydrated poly(HPB) was thermally stable up to 300°C. The electrical conductivity of I₂-doped dehydrated poly(HPB) was 10⁻² S cm⁻¹. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 949–953, 1998