Proton Conducting Membranes Based on Poly(2,2′‐imidazole‐5,5′‐bibenzimidazole)

Poly(2,2′‐imidazole‐5,5′‐bibenzimidazole) (PBI‐imi) was synthesized via the polycondensation between 3,3′,4,4′‐tetraaminobiphenyl and 4,5‐imidazole‐dicarboxylic acid. Effects of the reaction conditions on the intrinsic viscosity of the synthesized polymers were studied. The results show that the molecular weight of the polymers increases with increasing monomer concentration and reaction time, and then levels off. With higher reaction temperature, the molecular weight of the polymer is higher. With the additional imidazole group in the backbone, PBI‐imi shows improved phosphoric acid doping ability, as well as a little higher proton conductivity when compared with widely used poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI‐ph).Whereas, PBI‐imi and PBI‐ph have the similar chemical oxidation stability. PBI‐imi/3.0 H₃PO₄ composite membranes exhibit a proton conductivity as high as 10^–4 S cm^–1 at 150 °C under anhydrous condition. The temperature dependence of proton conductivity of acid doped PBI‐imi can be modeled by an Arrhenius equation.     

A copolymer of poly[2,2′‐(m‐phenylene)‐5,5′‐ bibenzimidazole] and poly(2,5‐benzimidazole) for high‐temperature proton‐conducting membranes

A novel copolymer of polybenzimidazoles was prepared by copolymerization of 3,3′‐diaminobenzidine tetrahydrochloride, 3,4‐diaminobenzoic acid and isophthalic acid in polyphosphoric acid at 200 °C. The polymerization could be performed within 90–110 min with the assistance of microwave irradiation. The solubility of the copolymer obtained in N,N‐dimethylacetamide (DMAc) was improved compared with those of poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] and poly(2,5‐benzimidazole). Thus copolymer membranes could be readily prepared by dissolving the copolymer powders in DMAc with refluxing under ambient pressure. The decomposition temperature of the copolymer was about 520 °C in air according to thermogravimetric analysis data. The proton conductivity and mechanical strength of the phosphoric acid‐doped copolymer membranes were investigated at elevated temperatures. A conductivity of 0.09 S cm^?1 at 180 °C and a tensile stress at break of 5.9 MPa at 120 °C were achieved for the acid‐doped copolymer membranes by doping acids in a 75 wt% H₃PO₄ solution. Copyright © 2010 Society of Chemical Industry     

Synthesis,Characterization and Application of New Rhodium Complexes for Indirect Electrochemical Cofactor Regeneration

Electroenzymatic synthesis often suffers from electrochemical reaction steps which proceed slower than the coupled enzyme reaction. For indirect electrochemical cofactor regeneration, we here report two new mediators with superior properties compared to the established rhodium complex (2,2′‐bipyridyl)(pentamethylcyclopentadienyl)rhodium [Cp*Rh(2,2′‐bipyridine)]. After constructing a robotic system for fast and reliable cyclic voltammetry measurements, we screened twelve rhodium complexes with substituted 2,2′‐bipyridine ligands for their reduction potentials and catalytic activity towards the reduction of NADP. Promising complexes were investigated in more detail by cyclic voltammetry and under batch electrolysis conditions. The new complexes Cp*Rh(5,5′‐methyl‐2,2′‐bipyridine) and Cp*Rh(4,4′‐methoxy‐2,2′‐bipyridine) reduced NADP to NADPH three times faster than the established mediator, resulting in volumetric productivities of up to 136 mmol L⁻¹ d⁻¹ and turnover frequencies of up to 113 h⁻¹. This increased reaction rate of these new mediators makes indirect electrochemical approach significantly more competitive to other methods of cofactor regeneration. Abbreviations: ADH=alcohol dehydrogenase; Ag|AgCl=silver|silver chloride reference electrode; bpy=2,2′‐bipyridine; ci=current increase; Cp*=pentamethylcyclopentadienyl; CV=cyclic voltammetry; Ep=peak potential; equiv=equivalent; NADP/NADPH=nicotinamide adenine dinucleotide phosphate oxidised/reduced form.     

A DFT Study on the Structures and Energies of Isomers of 4‐Amino‐1,3‐dinitro‐1,2,4‐triazol‐5‐one‐2‐oxide: New High Energy Density Compounds

Isomers of 4‐amino‐1,3‐dinitrotriazol‐5‐one‐2‐oxide (ADNTONO) are of interest in the contest of insensitive explosives and were found to have true local energy minima at the DFT‐B3LYP/aug‐cc‐pVDZ level. The optimized structures, vibrational frequencies and thermodynamic values for triazol‐5‐one N‐oxides were obtained in their ground state. Kamlet‐Jacob equations were used to evaluate the performance properties. The detonation properties of ADNTONO (D=10.15 to 10.46 km s⁻¹, P=50.86 to 54.25 GPa) are higher compared with those of 1,1‐diamino‐2,2‐dinitroethylene (D=8.87 km s⁻¹, P=32.75 GPa), 5‐nitro‐1,2,4‐triazol‐3‐one (D=8.56 km s⁻¹, P=31.12 GPa), 1,2,4,5‐tetrazine‐3,6‐diamine‐1,4‐dioxide (D=8.78 km s⁻¹, P=31.0 GPa), 1‐amino‐3,4,5‐trinitropyrazole (D=9.31 km s⁻¹, P=40.13 GPa), 4,4′‐dinitro‐3,3′‐bifurazan (D=8.80 km s⁻¹, P=35.60 GPa) and 3,4‐bis(3‐nitrofurazan‐4‐yl)furoxan (D=9.25 km s⁻¹, P=39.54 GPa). The  NH₂ group(s) appears to be particularly promising area for investigation since it may lead to two desirable consequences of higher stability (insensitivity), higher density, and thus detonation velocity and pressure.     

The Nitrolysis Mechanism of 3,7‐Dinitro‐1,3,5,7‐tetraazabicyclo[3,3,1]nonane

Two intermediates, 1,5‐dinitroso‐3,7‐dinitro‐1,3,5,7‐tetraazacyclooctane (DNDS) and 1‐nitroso‐3,5,7‐trinitro‐1,3,5,7‐tetraazacyclooctane (MNX), were isolated and characterized in the synthesis of 1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) from the nitrolysis of 3,7‐dinitro‐1,3,5,7‐tetraazabicyclo[3,3,1]nonane (DPT) for the first time. When the nitrolysis of DPT was slowed down, two intermediates were detected with HPLC. It was proposed that electrophilic NO₂⁺ and NO⁺ from HNO₃ and N₂O₄ might attack nitrogen atoms at positions 3 and 7 of DPT to form the cations of the intermediates, then nucleophilic H₂O attacked the bridge carbon atoms of DPT to produce the intermediates, which were oxidized to form HMX.     

Fluorescent chemosensor based on the conjugated polymer incorporating 2,2′‐bipyridyl moiety for transition metal ions

A fluorescent conjugated polymer was synthesized by the polymerization of 1,4‐dibromo‐2,3‐bisbutoxynaphthalene ( M‐2 ) with 5,5′‐divinyl‐2,2′‐bipyridine ( M‐3 ) via Heck reaction. The conjugated polymer shows strong blue–green fluorescence because of the extended π‐electronic structure between the repeating unit 2,3‐bisbutoxynaphthyl group and the conjugated linker 2,2′‐bipyridyl (bpy = 2,2′‐bipyridine) moiety via vinylene bridge. The responsive properties of the conjugated polymer on transition metal ions were investigated by fluorescent and UV–vis spectra. The results show that Cu²⁺ and Ni²⁺ can form nonradiative metal‐to‐ligand charge‐transfer complexes with the polymer, whereas, Zn²⁺ and Cd²⁺ do not produce the pronounced differences from the polymer fluorescence and UV–vis spectra. The fluorescent quenching can probably be attributed to the intramolecular photoinduced electron transfer (PET) or photoinduced charge transfer (PCT). The results can also suggest that 2,2′‐bipyridyl moiety in the main chain backbone of the conjugated polymer can act as the recognition site of a special fluorescent chemosensor for sensitive detection of transition metal ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of novel aromatic poly(amide‐imide)s derived from 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl or 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl and various aromatic diamines

New aromatic diimide‐dicarboxylic acids having kinked and cranked structures, 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl (2a) and 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl (2b), were synthesized by the reaction of trimellitic anhydride with 2,2′‐bis(4‐aminophenoxy)biphenyl (1a) and 2,2′‐bis(4‐aminophenoxy)‐1,1′‐binaphthyl (1b), respectively. Compounds 2a and 2b were characterized by FT‐IR and NMR spectroscopy and elemental analyses. Then, a series of novel aromatic poly(amide‐imide)s were prepared by the phosphorylation polycondensation of the synthesized monomers with various aromatic diamines. Owing to structural similarity, and a comparison of the characterization data, a model compound was synthesized by the reaction of 2b with aniline. The resulting polymers with inherent viscosities of 0.58–0.97 dl g^?1 were obtained in high yield. The polymers were fully characterized by FT‐IR and NMR spectroscopy. The ultraviolet λ_max values of the poly(amide‐imide)s were also determined. The polymers were readily soluble in polar aprotic solvents. They exhibited excellent thermal stabilities and had 10% weight loss at temperatures above 500 °C under a nitrogen atmosphere. Copyright © 2003 Society of Chemical Industry     

Effects of the solvent polarity on the atom transfer radical polymerization of methyl methacrylate initiated by 4‐(chloromethyl)phenyltrimethoxysilane

The controllability of the atom transfer radical polymerization of methyl methacrylate in the polar solvent N,N‐dimethylformamide and the nonpolar solvent xylene with 4‐(chloromethyl)phenyltrimethoxysilane as an initiator and with CuCl/2,2′‐bipyridine and CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as catalyst systems was studied. Gel permeation chromatography analysis established that in the nonpolar solvent xylene, much better control of the molecular weight and polydispersity of poly(methyl methacrylate) was achieved with the CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine catalyst system than with the CuCl/2,2′‐bipyridine as catalyst system. In the polar solvent N,N‐dimethylformamide, unlike in xylene, the polymerization was more controllable with the CuCl/2,2′‐bipyridine catalyst system than with the CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine catalyst system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2751–2754, 2007     

Blue‐light‐emitting poly(arylene ethynylenes) containing alternating sequences of biphenylene or fluorenediyl and p‐phenylene moieties linked through triple bonds

Two new poly(arylene ethynylenes) were synthesized by the reaction of 1,4‐diethynyl‐2.5‐dioctylbenzene either with 4,4′‐diiodo‐3,3′‐dimethyl‐1,1′‐biphenyl or 2,7‐diiodo‐9,9‐dioctylfluorene via the Sonogashira reaction, and their photoluminescence (PL) and electroluminescence (EL) properties were studied. The new poly(arylene ethynylenes) were poly[(3,3′‐dimethyl‐1,1′‐biphenyl‐4,4′‐diyl)‐1,2‐ethynediyl‐(2,5‐dioctyl‐1,4‐phenylene)‐1,2‐ethynediyl] (PPEBE) and poly[(9,9‐dioctylfluorene‐2,7‐diyl)‐1,2‐ethynediyl‐(2,5‐dioctyl‐1,4‐phenylene)‐1,2‐ethynediyl] (PPEFE), both of which were blue‐light emitters. PPEBE not only emitted better blue light than PPEFE, but it also performed better in EL than the latter when the light‐emitting diode devices were constructed with the configuration indium–tin oxide/poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonic acid) (50 nm)/polymer (80 nm)/Ca:Al. The device constructed with PPEBE exhibited an external quantum efficiency of 0.29 cd/A and a maximum brightness of about 560 cd/m², with its EL spectrum showing emitting light maxima at λ = 445 and 472 nm. The device with PPEFE exhibited an efficiency of 0.10 cd/A and a maximum brightness of about 270 cd/m², with its EL spectrum showing an emitting light maximum at λ = 473 nm. Hole mobility (μ_h) and electron mobility (μ_e) of the polymers were determined by the time‐of‐flight method. Both polymers showed faster μ_h values. PPEBE revealed a μ_h of 2.0 × 10^?4 cm²/V·s at an electric field of 1.9 × 10⁵ V/cm and a μ_e of 7.0 × 10^?5 cm²/V·s at an electric field of 1.9 × 10⁵ V/cm. In contrast, the mobilities of the both carriers were slower for PPEFE, and its μ_h (8.0 × 10^?6 cm²/V·s at an electric field of 1.7 × 10⁶ V/cm) was 120 times its μ_e (6.5 × 10^?8 cm²/V·s at an electric field of 8.6 × 10⁵ V/cm). The much better balance in the carriers' mobilities appeared to be the major reason for the better device performance of PPEBE than PPEFE. Their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels were also a little different from each other. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 299–306, 2006     

Mechanical and thermal characterization of iron(II) 2,2′‐bipyridine complex supported polyacrylonitrile fiber as a novel photocatalyst

In this study, the mechanical and thermal properties of amidoximated polyacrylonitrile fibers immobilized with iron(II) 2,2′‐bipyridine complex (Fe(bpy)₃²⁺) have been investigated to support their commercial application for wastewater treatment. The mechanical properties were evaluated with respect to breaking strength and elongation at break in both dry and wet conditions. Dynamic mechanical analysis, differential scanning calorimetry, and thermogravimetric analysis techniques were used to determine the thermal behavior. The results indicate the effect of Fe(bpy)₃²⁺ immobilization on the breaking strength of the dry fiber samples were negligible, and the corresponding elongation at break decreased gradually with Fe(bpy)₃²⁺ content increasing. In addition, water treatment greatly affected the mechanical properties of the fibrous materials. Thermal studies reveal that Fe(bpy)₃²⁺ immobilization led to better fiber thermal stabilization in terms of higher storage modulus at high temperature regions, larger glass transition temperature, and smaller weight loss. The 2,2′‐bipyridine ligands were found to be responsible for the better mechanical and thermal performance of the fibrous materials by enhancing the intermolecular crosslink. POLYM. ENG. SCI., 55:1052–1058, 2015. © 2014 Society of Plastics Engineers     

Preparation of organo‐soluble poly[(2,2′‐m‐phenylene)‐5,5′‐bibenzimidazole] with high yield by homogeneous nitration reaction

To prepare organo‐soluble poly[(2,2,′‐m‐phenylene)‐5,5′‐bibenzimidazole] (PBI) with high yield, a homogeneous nitration of PBI was attempted. Nitro‐substituted PBI (NO₂‐PBI) was synthesized through the homogeneous reaction of the PBI powder with nitric acid in sulfuric acid. The degree of substitution (DS) of this NO₂‐PBI is higher than that of the NO₂‐PBI prepared through the heterogeneous reaction of the PBI fiber. The viscosity of the NO₂‐PBI prepared through the homogeneous reaction decreased with increasing amount of nitric acid added. The DS of the NO₂‐PBI reached the maximum value of 2. The substitution efficiency of nitro groups decreased as the amount of nitric acid added increased. When a small quantity of nitric acid was added, the substitution of the sulfonic acid group was confirmed as well as that of the nitro group. The solubility of the NO₂‐PBI depended strongly on the DS. The NO₂‐PBI having the DS of about 2 was completely soluble in dimethylacetamide and almost soluble in N‐methylpyrrolidone. At an elevated temperature, it was also soluble in other polar aprotic solvents such as dimethylformamide and dimethylsulfoxide. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 438–445, 2000     

Optoelectronic properties of thiazole‐based polythiophenes

In this work, two thiazole‐containing monomers N‐(thiazol‐2‐yl)?2‐(thiophen‐3‐yl)acetamide (ThDBTH) and N,N′‐([4,4′‐bithiazole]‐2,2′‐diyl)bis(2‐(thiophen‐3‐yl)acetamide) (Th₂DBTH) were synthesized through amidification reaction of 2‐(thiophen‐3‐yl)acetyl chloride with aminothiazole derivatives and characterized by FTIR and ¹H and ¹³C‐NMR. The monomers were subjected to electrochemical polymerization and optoelectronic properties of the resultant conducting polymers were investigated. Additionally, copolymerization of ThDBTH in the presence of thiophene was achieved. PThDBTH, PTh₂DBTH, and P(ThDBTH‐Th) exhibited optical band gaps of 2.15, 2.30, and 1.95 eV, respectively. Switching time and optical contrast of the polymers were evaluated via kinetic studies. The P(ThDBTH‐Th) revealed satisfactory switching time and appropriate optical contrast of 1.27 s and 24.97%, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42206.     

Highly Active and Enantioselective Rhodium‐Catalyzed Asymmetric 1,4‐Addition of Arylboronic Acid to α,β‐ Unsaturated Ketone by using Electron‐Poor MeO‐F12‐BIPHEP

The asymmetric 1,4‐addition of phenylboronic acid to cyclohexenone were performed by using a low amount of rhodium/(R)‐(6,6′‐dimethoxybiphenyl‐2,2′‐diyl)bis[bis(3,4,5‐trifluorophenyl)phosphine] (MeO‐F₁₂‐BIPHEP) catalyst. Because the catalyst shows thermal resistance at 100 °C, up to 0.00025 mol% Rh catalyst showed good catalytic activity. The highest turnover frequency (TOF) and turnover number (TON) observed were 53,000 h⁻¹ and 320,000, respectively. The enantioselectivities of the products were maintained at a high level of 98% ee in these reactions. The Eyring plots gave the following kinetic parameters (ΔΔH^≠=−4.0±0.1 kcal mol⁻¹ and ΔΔS^≠=−1.3±0.3 cal mol⁻¹ K⁻¹), indicating that the entropy contribution is relatively small. Both the result and consideration of the transition state in the insertion step at the B3LYP/6‐31G(d) [LANL2DZ for rhodium] levels indicated that the less σ‐donating electron‐poor (R)‐MeO‐F₁₂‐BIPHEP could be creating a rigid chiral environment around the rhodium catalyst even at high temperature.     

Dependence of optical properties on the preparation methods of poly[(9,9′‐dialkylfluorene‐2,7‐diyl)‐alt‐(1,3,4‐oxadiazole‐2,5‐diyl)]

A blue‐light‐emissive fluorene‐based polyoxadiazole, an n‐type polyfluorene derivative, was synthesized by both one‐step and two‐step methods. Directly polymerized poly[(9,9′‐didodecylfluorene‐2,7‐diyl)‐alt‐(1,3,4‐oxadiazole‐2,5‐diyl)] (PFOx‐DP) exhibited a higher molecular weight and a more efficient photoluminescence quantum yield than poly[(9,9′‐didodecylfluorene‐2,7‐diyl)‐alt‐(1,3,4‐oxadiazole‐2,5‐diyl)] (PFOx) prepared via a polyhydrazide precursor, poly[9,9′‐didodecylfluorene‐2,7‐(2,5‐dihydrazide‐ 1,3,4‐oxadiazole). Both polymers, differently prepared, showed similar photoluminescent properties in 1,2‐dichloroethane. However, in a film state, the influence of the interchain interactions on the photoluminescence of PFOx with the lower molecular weight was larger than on the photoluminescence of PFOx‐DP. The electron‐deficient property of an oxadiazole group in the polymer backbone resulted in low‐lying highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of ?6.29 and ?3.26eV, respectively, of the polymer suitable for electron‐transport/hole‐blocking layers and emissive layers in multilayer electroluminescence devices. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3112–3118, 2004     

Synthesis,characterization, electrochemistry and optical properties of a novel phenanthrenequinone‐ alt‐dialkylfluorene conjugated copolymer

This paper describes the synthesis, characterization and electro‐optical properties of a 9,10‐phenanthrenequinone (PQ)‐containing alternating conjugated copolymer: poly[(9,10‐phenanthrenequinone‐2,7‐diyl)‐alt‐(9,9‐di‐n‐hexylfluorene‐2,7‐diyl)] (PPQF). The copolymer has good solubility in common organic solvents such as CH₂Cl₂, CHCl₃ and tetrahydrofuran. The polymer structure was determined using ¹H NMR, Fourier transform infrared spectroscopy, gel permeation chromatography and elemental analysis. The polymer possesses a low‐energy n → π* electronic state caused by the C?O groups of the PQ repeating units, and exhibits interesting and improved electrochemical reduction activity as compared to poly(9,9‐di‐n‐hexylfluorene‐2,7‐diyl) and molecular PQ. PPQF has no fluorescence in solution but shows interesting transitions from no fluorescence to strong fluorescence after it undergoes electrochemical reduction. The polymer PPQF may find use as a starting material for a range of applications and can also be used to prepare other polymers due to the presence of the PQ repeating units. Copyright © 2007 Society of Chemical Industry     

Copolymers of Poly(2,5‐benzimidazole) and Poly[2,2′‐(p‐phenylene)‐5,5′‐bibenzimidazole] for High‐Temperature Fuel Cell Applications

Copolymers of poly(2,5‐benzimidazole) (ABPBI) and poly[2,2′‐(p‐phenylene)‐5,5′‐bibenzimidazole] (pPBI) were synthesized for use as fuel cell membranes to take advantage of the properties of both constituents. The composition of the copolymers were controlled by changing the feed ratio of 3,4‐diaminobenzoic acid and terephthalic acid with 3,3′‐diaminobenzidine in the polycondensation reaction. The copolymer membranes showed higher conductivities, better mechanical properties, and larger acid absorbing abilities than commercial poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] membranes.

     

Comportement electrochimique et reactivite du systeme Ag(II)/Ag(I)-bipyridine dans le carbonate de propylene—III. Etude du mecanisme et de la cinetique de la reaction d'oxydation catalytique de la bipyridine

The electrochemical behaviour of the Ag(II)/Ag(I)-bipyridine system has been investigated in solutions containing bipyridine in excess with respect to the Ag⁺-bipy: 1–2 stoichiometry. The nature of the coupled chemical reaction indicates a chemical catalysis of an electrochemical reaction. The rate constant of the reaction of destruction of the intermediate complex (k₂ = 1.8 × 10^?3s^?1) has been calculated from measurements performed during electrolysis of Ag^I(bipy)⁺₂-bipy solutions.     

Synthesis of polyacrylonitrile via reverse ATRP initiated by 1,1,2,2‐tetraphenyl‐1,2‐ethanediol/CuCl2/2,2′‐bipyridine

The reverse atom‐transfer radical polymerization (RATRP) technique using CuCl₂/2,2′‐bipyridine (bipy) complex as a catalyst was applied to the living‐radical polymerization of acrylonitrile (AN). 1,1,2,2‐Tetraphenyl‐1,2‐ethanediol (TPED) was first used as the initiator in this copper‐based RATRP initiation system. A CuCl₂ to bipy ratio of 0.5 not only gives the best control of molecular weight and its distribution, but also provides rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 53.2 kJ mol^?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed the chain extension polymerization in the presence of CuCl/bipy catalyst system via a conventional ATRP process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3529–3533, 2007     

Nonlinear optical studies on new conjugated poly{2,2l‐(3,4‐ dialkoxythiophene‐2,5‐diyl) bis[5‐(2‐thienyl)‐1,3,4‐oxadiazole]}s

Three new donor–acceptor type poly{2,2^l‐(3,4‐ dialkoxythiophene‐2,5‐diyl)bis[5‐(2‐thienyl)‐1,3,4‐oxadiazole]}s ( P1, P2, and P3 ) were synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. The polymerization was carried out using chemical polymerization technique. The optical and charge‐transporting properties of the polymers were investigated by UV‐visible, fluorescence emission spectroscopic and cyclic voltammetric studies. The polymers showed bluish‐green fluorescence in solutions. The electrochemical band gaps were determined to be 2.03, 2.09, and 2.17 eV for P1 , P2, and P3, respectively. The nonlinear optical properties of new polymers were investigated at 532 nm using single beam Z‐scan and degenerate four‐wave mixing (DFWM) techniques with nanosecond laser pulses. The polymers exhibited strong optical limiting behavior due to “effective” three‐photon absorption. Values of the effective three‐photon absorption ( 3PA ) coefficients, third‐order nonlinear susceptibilities (χ⁽³⁾), and figures (F) of merit were calculated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Determination potentiometrique des constantes de stabilite des complexes entre l'argent(I) et quelques heterocycles azotes en milieu neutre et acide dans le carbonate de propylene

The formation of AgL⁺_n (n = 1–4) (L = pyridine), AgL′⁺ and AgL′₂⁺ [L′ = 2,2′ bipyridine, 2,2′ biquinoline, 2-(2-pyridyl)benzimidazole] complexes has been studied using potentiometry with a silver electrode. The acidity constants of the ligands have been measured potentiometrically with the hydrogen electrode. The silver distribution between the Ag⁺ and AgL_n⁺ species has been computed by means of the so obtained β_n. In acidic medium, the metallic complexes are destroyed by the ligand protonation.