Preparation of π-conjugated polymers consisting of 1-aminopyrrole and 4-amino-1,2,4-triazole units

π-Conjugated polymers based on 1-aminopyrrole and 4-amino-1,2,4-triazole were prepared. Pd-catalyzed organometallic polycondensation gave poly(arylene-ethynylene) (PAE)-type π-conjugated polymers consisting of BOC-protected 4-amino-1,2,4-triazole (Taz(BOC)) units (BOC = t-butoxycarbonyl). The number average molecular weights (M_n) were determined to be 5200–19,200 using GPC. An alternating copolymer of Taz(BOC) and bithiophene (Th–Th) units, P(Taz(BOC)-Th-Th)_n-Pd, with an M_n of 10,800 was also prepared by Pd-catalyzed organometallic polycondensation. (Taz(BOC)-Th-Th)_n-Pd showed a UV–Vis absorption peak at λ_max = 425 nm, which is reasonable for a π-conjugated five-membered ring polymer with a coplanar structure. The deprotection of the BOC group of the polymers proceeded at 200 °C; this BOC-deprotection was investigated using a model compound. The optical and electrochemical properties of the π-conjugated polymers are reported.     

Synthesis of π-conjugated polymers bearing electronic and optical functionalities by organometallic polycondensations and their chemical properties

A wide variety of π-conjugated polymers have been synthesized by using organometallic polycondensations. For instance, Ni(0) complex-promoted dehalogenative polycondensation of dihaloaromatic compounds, X-Ar-X, affords poly(arylene)s, -(Ar)_n-. Pd-catalyzed polycondensation gives alternating copolymers, -(Ar-Ar′)_n-, and poly(arylene-ethynylene)s, -(Ar-CC-Ar′-CC)_n-. These polymers show distinguishing optical and electrochemical properties and functionalities. Their well-characterized linear structures lead to molecular assembly and packing of the polymer molecules in solutions and in the solid state. In this article, we describe the synthesis of π-conjugated polymers by the organometallic polycondensations, chemical properties of the synthesized polymers, and applications of the polymers for electronic and optical devices.     

Synthesis and optical properties of π-conjugated polymers composed of diester-substituted bithiophene and dibenzothiophene or carbazole

Novel π-conjugated polymers composed of diester-subsituted bithiophene and dibenzothiophene (PDBT-DEBT) or N-alkyl carbazole (PCz-DEBT) were prepared via the Stille cross-coupling polymerization using Pd(0) catalyst. The structures of obtained polymers were confirmed by ¹H NMR and IR spectroscopies. Optical properties of the polymers were investigated by UV–vis and photoluminescence spectroscopies. The photoluminescence spectra of the polymers showed strong emission peaks in the green region.     

Preparation and properties of new π-conjugated polyquinoxalines with aromatic fused rings in the side chain

Summary New π-conjugated polyquinoxalines with aromatic fused rings in their side chain have been prepared. Dehalogenative organometallic polycondensation of 5,8-dibromo[2,3-b]-acenaphthenequinoxaline and 5,8-dibromo[2,3-b]phenanthrenequinoxaline with a zerovalent nickel complex afforded poly([2,3-b]acenaphthenequinoxaline-5,8-diyl) (P(5,8-Qx(ace))) and poly([2,3-b]phenanthrenequinoxaline-5-8-diyl) (P(5,8-Qx(phen))) in high yields. P(5, 8-Qx(ace)) had an [η] value of 0.23 dL g⁻¹ and showed absorption and photoluminescence peaks at 445 and 565 nm, respectively. (P(5,8-Qx(phen))) gave absorption and photoluminescence peaks at 400 and 514 nm, respectively. XRD data indicated formation of ordered structures of the polymers in the solid. Preparation of related copolymer with thiophene is also reported. Received: 15 February 2000/Accepted: 2 March 2000     

Preparation and chemical properties of π-conjugated poly(1,10-phenanthroline-3,8-diyl)s with crown ether subunits

π-Conjugated polymers consisting of 1,10-phenanthroline units and crown ether subunits (Poly-1, Poly-2, and Poly-3) were prepared by dehalogenation polycondensation of the corresponding dibromo monomers using a zero-valent nickel complex as a condensing agent. They were characterized by elemental analysis, ¹H NMR and UV–Vis spectroscopies, and cyclic voltammetry (CV). They were partly soluble in CHCl₃, and the number average molecular weight of the soluble part of Poly-2, which had 15-crown-5 subunits, was estimated to be 5300. The polymers exhibited UV–Vis peaks at approximately λ_max = 360 nm, which was reasonable. Complexation with [Ru(bpy)₂]²⁺ and alkaline metal ions made the polymer soluble in organic solvents. The complexation of [Ru(bpy)₂]²⁺ to the 1,10-phenanthroline unit proceeded quantitatively, and the [Ru(bpy)₂]²⁺ complexes exhibited CV curves characteristic of [Ru(N-N)₃]²⁺ complexes.     

New π-conjugated polymers containing oxazole in the main chain: Optical and electrochemical properties

Oxazole-containing π-conjugated polymers, an alternating copolymer of 9,9-dioctylfluorene-2,7-diyl and 2,5-bis(p-phenylene)oxazole (P(Flu-DPOxz)) and an alternating copolymer of 2,5-dialkoxy-p-phenylene and 2,5-bis(p-phenylene(oxazole)) (P(ROPh-DPOxz)), have been synthesized by Pd-catalyzed organometallic polycondensation. They were soluble in organic solvents, and had number average molecular weights of 18?600 and 24?700, respectively, in GPC analysis. P(Flu-DPOxz) and P(ROPh-DPOxz) showed UV-vis absorption peaks at about 380 nm in CHCl₃. Powder XRD patterns and UV-vis data of the polymers indicated that the polymer solid was amorphous. The polymers were photoluminescent both in chloroform and in solid. In chloroform, the emission peak appeared at about 420 nm with a high quantum yield of about 70%. The polymers were electrochemically active, and electrochemical data revealed that the oxazole unit behaved as a moderate electron-accepting unit.     

Synthesis of novel π-conjugated boron polymers containing transition metal in the main chain and their optical properties

Summary Novel π-conjugated boron polymers containing transition metals in the main chain were prepared by hydroboration polymerization between tetrayne monomer including metal complex and tripylborane. From gel permeation chromatographic analysis (THF, PSt standards), the number-average molecular weights of the polymers obtained were found to be 9,000. The polymers were soluble in common organic solvents such as THF, chloroform and benzene. The absorption peaks due to π-π^* transition were observed around 390nm in the UV-vis spectra of these polymers. The fluorescence emission spectra exhibited intense peaks at 490nm (in chloroform, room temperature, excitation wavelength at 390nm). Received: 16 April 2001/Accepted: 27 April 2001     

Designing π-conjugated polymers for organic electronics

Conjugated polymers have attracted an increasing amount of attention in recent years for various organic electronic devices because of their potential advantages over inorganic and small-molecule organic semiconductors. Chemists can design and synthesize a variety of conjugated polymers with different architectures and functional moieties to meet the requirements of these organic devices. This review concentrates on five conjugated polymer systems with 1D and 2D topological structures, and on one polymer designing approach. This includes (i) conjugated polyphenylenes (polyfluorenes, polycarbazoles, and various stepladder polymers), (ii) other polycyclic aromatic hydrocarbons (PAHs) as substructures of conjugated polymers, (iii) thiophene and fused thiophene containing conjugated polymers, (iv) conjugated macrocycles, (v) graphene nanoribbons, and finally (vi) a design approach, the alternating donor–acceptor (D–A) copolymers. By summarizing the performances of the different classes of conjugated polymers in devices such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and polymer solar cells (PSCs), the correlation of polymer structure and device property, as well as the remaining challenges, will be highlighted for each class separately. Finally, we summarize the current progress for conjugated polymers and propose future research opportunities to improve their performance in this exciting research field.     

New soluble π-conjugated polymers containing 2-diisopropylamino-1,3,5-triazine unit: synthesis,characterization and optical properties

A new type of π-conjugated polymers containing 2-diisopropylamino-1,3,5-triazine were prepared via Sonogashira or Suzuki coupling reaction. The structures of the polymers were performed by FT-IR, ¹H-NMR, UV–vis spectroscopy, photoluminescence spectroscopy, gel permeation chromatography, thermal analysis and X-ray diffraction analysis. These derived polymers were soluble in common organic solvents such as tetrahydrofuran, chloroform, toluene, and showed good thermal stability. Polymers containing 1,4-diethynyl-2,5-bis(dialkoxy)benzene unit in polymer main chain emitted blue-green light in solution phase under UV light irradiation except with polymer containing 9,9-dioctylfluorene(blue light). Acidochromic behaviors of polymers were studied in CHCl₃-CF₃COOH mixtures. 9,9-Dioctylfluorene-containing polymer displayed better acidochromic property and linear relationship between absorbance and concentration with the concentration of CF₃COOH from 5.384?×?10^?4 to 26.92?×?10^?4 mol/L. Electrochemical behaviors of polymers depicted p-doping and some hole-transporting properties. XRD results showed that polymers exhibited certain crystallinity.     

Synthesis of π-conjugated organoboron polymers by haloboration-phenylboration polymerization of aromatic diynes

π-Conjugated organoboron polymers were prepared by haloboration-phenylboration polymerization beween diyne monomers and bromodiphenylborane. The polymerization was carried out by adding a slightly excess amount of bromodiphenylborane to a tetrachloroethane solution of diynes at room temperature under nitrogen and stirring the reaction mixture for 4 hours at 100°C. The obtained polymers were soluble in common organic solvents such as THF and chloroform. Their molecular weights were estimated to be several thousands by gel permeation chromatographic analysis. In UV-vis absorption spectra, bathochromic shift of λ_max and absorption edge in comparison with the corresponding monomers were observed, which indicates the π-conjugation via vacant p-orbital of boron atom.     

A critical theoretical study on linear and nonlinear optical properties of macrocyclic thiophene derivatives with different connecting π-conjugated bridge and ring size

This contribution reports the geometries, electronic structures, linear and nonlinear optical properties of a series of macrocyclic thiophene derivatives with different connecting π-bridge and ring size in theory. It provides great optical properties that both OPA and TPA peaks shift red as Ne increases and in different window, which don't superimpose on each other, and the values of δ⁽¹⁾_max and δ⁽²⁾_max enlarge, while the largest δ⁽²⁾_max for C[6T_A_E]₃ observed at long wavelength (725.9 nm) is 23 times larger than that of the unit C[6T_A_E]. Besides connecting bridge and ring size, several key parameters essentially influencing on NLO property were highlighted, including M_0k, M_kn, ?_0k × ?_kn and Ne. In addition, ICT impacting on the values of δ⁽²⁾_max was analyzed by contour surfaces of the frontier orbitals and ΔQ of thiophene and bridge. More particularly, large negative value of Reγ indicates their self-defocusing, implying it can be applied in self-defocusing optical power limiting materials.     

Synthesis of fluorene- and anthracene-based π-conjugated polymers and dependence of emission range and luminous efficiency on molecular weight

In the present work poly[9,9-dioctylfluorene-co-2-pentyl-9,10-bis(4-vinylphenyl)anthracene], a fluorene- and anthracene-based copolymer, is synthesized through a Heck coupling reaction. In order to synthesize polymers with high-molecular weight, DMF (P1), DMF/p-Xylene = 1/1 (P2), p-Xylene (P3), and 1,4-Dioxane (P4) are used as solvents, which are an important factor in the synthesis process. The number of average molecular weights (M_n) of the synthesized polymers P1–P4 do not differ significantly, standing at 22,309, 12,369, 29,192, and 39,464, respectively, while their weight average molecular weights (M_w) show considerable differences (i.e. 50,055; 24,042; 125,406; and 231,053). Polymers P1–P4 demonstrate little difference in the results of a thermal analysis, electrochemical analysis, UV–vis analysis, and photoluminescence (PL) spectrum measurement. With regard to electroluminescence (EL) spectrum measurement, however, P1 and P2 show main luminous peaks at 508 nm, while P3 and P4's luminous peaks are seen at 516 nm. Moreover, luminous shoulder peaks were red-shifted with increase of molecular weight of polymers from 460 to 544 nm. In this process, the luminous area is red-shifted from greenish-blue to yellowish-green. The I–V–L measurement results show that the maximum brightness of P1, P2, and P3 ranges from 164 to 303 cd/m² and their luminous efficiency is low at 0.031–0.054 cd/A. Meanwhile, the turn-on voltage of P4, having greater molecular weight, is 9.5 V, and its maximum brightness and corresponding luminous efficiency are 736 cd/m² and 0.08 cd/A, respectively, implying that the luminous efficiency of devices improves as the molecular weight becomes greater.     

Imide/amide based π-conjugated polymers for organic electronics

Recently, great progress has been made in the field of organic electronics. Such advancements would not be possible without the synthesis of new donor–acceptor π-conjugated polymers. In this review, we summarize recent developments in the preparation of imide/amide containing polymers and their applications in bulk heterojunction (BHJ) solar cells and, to some extent, in organic field effect transistors (OFET).     

Synthesis and properties of nonlinear optical chromophores and polymers containing 6-nitroquinoline as π-electron acceptor

Summary Two nonlinear optical (NLO) methacrylate monomers, 2-methyl-acrylic acid 2-(ethyl-{4-[2-(6-nitro-quinolin-2-yl)-vinyl]-phenyl}-amino)-ethyl ester (5) and 2-methyl-acrylic acid 6-{3-[2-(6-nitro-quinolin-2-yl)-vinyl]-carbazol-9-yl}-hexyl ester (7) were newly synthesized and copolymerized with methylmethacrylate to give NLO polymers, P1 and P2. These polymers were well soluble in organic solvents and showed glass transition temperatures at 145 °C and 114 °C, respectively. The number average molecular weights (Mn) were 26,600 for P1 and 9,300 for P2. The SHG coefficients (d₃₃) of corona-poled films of P1 and P2 measured with 1.064 μm Nd-YAG laser were 32.2 pm/V and 17.6 pm/V, respectively. Received: 29 September 1998/Revised version: 7 December 1998/Accepted: 11 December 1998     

π-conjugated polymers containing pendant Mn12 cluster: Synthesis and physical properties

In this paper two conjugated polymers containing polyfluorene chain with pendant carboxyl group (P1 and P2) are synthesized via Suzuki reaction, and then two corresponding polymers containing the pendant Mn₁₂ cluster core (Mn₁₂-P1 and Mn₁₂-P2) are obtained through exchange of the pendant carboxyl group in the polymers with acetate ligand of Mn₁₂-Ac. All the polymers show similar UV–vis absorption spectra with maximum peak at 388 nm and fluorescence emission spectra with maximum peak at 419 nm and a shoulder at 443 nm that can be attributed to the polyfluorene chain. The cyclic voltammetry measurement indicates that Mn₁₂-P1 or Mn₁₂-P2 exhibit similar electrochemical behavior to that of the corresponding P1 or P2. These indicate that the introduction of Mn₁₂ cluster at the side-chain of the conjugated polymers has little influence on the photophysical and electrochemical properties of the conjugated main-chain. However, compared with pristine Mn₁₂-Ac the magnetic properties of the modified Mn₁₂ cluster has been changed after substitution of acetate group by the pendant carboxyl group of the polymer. Both of the Mn₁₂ clusters modified by the conjugated polymer (Mn₁₂-P1 and Mn₁₂-P2) show paramagnetism in the range of 2–300 K, and no SMM magnetic behavior is observed at low temperature.     

Low-bandgap copolymers consisting of 2,1,3-benzoselenadiazole and carbazole derivatives with thiophene or selenophene π-bridges

Two donor–acceptor-type alternating copolymers consisting of 2,1,3-benzoselenadiazole and carbazole derivatives with thiophene or selenophene π-bridges were synthesized by Suzuki cross-coupling polymerization, and their optical, electrochemical, and photovoltaic properties were compared. The selenophene π-bridged copolymer (PCz-DSeBSe) exhibited a smaller band-gap (1.82 eV) than the thiophene-bridged polymer (PCz-DTBSe; 1.89 eV). PCz-DSeBSe also showed a deeper highest occupied molecular orbital energy level (−5.36 eV) than PCz-DTBSe (−5.20 eV). Moreover, the PCz-DSeBSe thin film showed higher crystallinity and hole mobility than the PCz-DTBSe thin film. Organic photovoltaic devices were fabricated using the polymers as the donors and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) as the acceptor. The device using PCz-DSeBSe showed a higher open circuit voltage (V_oc), short circuit current density (J_sc), and power conversion efficiency (PCE) than that using PCz-DTBSe. The fabricated indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/PCz-DSeBSe:PC₇₁BM/LiF/Al device showed the maximum PCE of 2.88% with a J_sc of 7.87 mA/cm², an V_oc of 0.80 V, and a fill factor of 0.50 under AM 1.5G irradiation (100 mW/cm²).     

Doping behavior of water-soluble π-conjugated polythiophenes depending on pH and interaction of the polymer with DNA

Doping behavior of two kinds of water-soluble polythiophenes (PThs) (PTh with a CH₂CH₂CH₂SO₃M substituent at the 3-position, P3(RSO₃H)Th, and poly(ethylenedioxythiophene), PEDOTh) has been investigated spectroscopically at various pH under air. The p-doped (or oxidized) state of P3(RSO₃M)Th is stable at pH=1.0, whereas at pH levels higher than 4, the polymer is undoped. To the contrary, the p-doped state of PEDOTh is stable over a pH range of 1 to 7. Mixing of PEDOTh and a DNA (poly(G-C)₂) in a Tris buffer solution leads to a change of the UV-visible spectrum and precipitation of their adduct, supporting formation of an adduct between PEDOTh and poly(G-C)₂.     

Preparation and study of the mechanical and optical properties of infrared transparent Y2O3–MgO composite ceramics

In this study, fine Y₂O₃–MgO composite nanopowders were synthesized via the sol–gel method. Dense Y₂O₃–MgO composite ceramics were fabricated by pre-sintering the green body in air at different temperatures for 1 h and then subjecting the sintered bodies to hot isostatic pressing at 1300°C for 1 h. The effects of pre-sintering temperature on the microstructural, mechanical, and optical properties of the resulting ceramics were studied. The average grain size of the ceramics was increased, whereas their hardness and fracture toughness were decreased with increasing pre-sintering temperature. A maximum fracture toughness of 1.42 MPa·m^1/2 and Vickers hardness of 10.4 GPa were obtained. The average flexural strength of the ceramics was 411 MPa at room temperature and reached 361 MPa at 600°C. A transmittance of 84% in the 3–5 µm region was obtained when the composite ceramics were sintered at 1400°C. Moreover, a transmittance of 76% in the 3–5 µm region was obtained at 500°C.     

Preparation and properties of eggshell/β-polypropylene bio-composites

In this article, a novel eggshell/β-PP bio-composite was prepared and evaluated. First the waste chicken eggshell (ES) was modified by a stingy amount of pimelic acid (PA) through solution method, and then compounded with PP through melt blending method. The crystalline form, mechanical properties, and morphology of the ES/β-PP composites were studied. The results showed that ES modified by PA was a β nucleating agent with high efficiency and selectivity, resulting in the maximum K_β value of 0.99 in PP composites. PA modification promoted the dispersion and interfacial bonding of ES in PP. Although the addition of PA-modified ES slightly decreased tensile properties and flexural properties of PP, it increased the impact strength of PP by 228% than that of pure PP. Taking all factors into consideration, the optimal mass ratio of PP/ES/PA composites for reaching optimum mechanical properties should be 100/5/0.000471. Thus, the application of modified ES to prepare ES/β-PP bio-composites represents a promising way to mitigate environmental pollution and to reduce the cost of polyolefin products. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and thermoelectric properties of Bi2SexTe3−x bulk materials

Bi₂Te₃ and Bi₂Se₃ nanoplates were synthesized by a microwave-assisted wet chemical method, and Bi₂Se_xTe_3−x (x=1, 2, 3) bulk nanocomposites were then prepared by hot pressing the Bi₂Te₃ and Bi₂Se₃ nanoplates at 80 MPa and 723 K in vacuum. The phase composition and microstructures of the bulk samples were characterized by powder X-ray diffraction and field-emission scanning electron microscopy, respectively. The electrical conductivity of the Bi₂Se_xTe_3−x bulk nanocomposites increases with increasing Se content, and the Seebeck coefficient value is negative, showing n-type conduction. The absolute Seebeck coefficient value decreases with increasing Se content. A highest power factor, 24.5 µWcm⁻¹ K⁻², is achieved from the sample of x=1 at 369 K among the studied samples.