Electrodeposition of PbO2 and Bi–PbO2 on Ebonex

Electrodeposition of PbO2 and Bi–PbO2 on Ebonex was carried out under various conditions, and the surfaces and coating/substrate interfaces examined by SEM, XPS and SIMS. Excellent adhesion to Ebonex was obtained with both crystalline and amorphous surfaces. Low plating temperatures resulted in dark grey, bright PbO2 and black, mirror-like Bi–PbO2 surfaces. Extrapolation of electrode lifetime test data indicated corrosion rates of 716 m yr–1 for PbO2 and 158 m yr–1 for Bi–PbO2.     

Studies on Cure Kinetics of Diglycidyl Ether of 4,4′-Bisphenol/4,4′-Diaminobiphenyl Using the Advanced Isoconversional Method

The cure kinetics of a rigid-rod epoxy monomer, diglycidyl ether of 4,4′-bisphenol (DGEBP), and the curing agent with the similar rigid-rod group, 4,4′-diaminebiphenyl (DABP), was studied using an advanced isoconversional method (AICM). DGEBP/DABP curing system was carried out by means of differential scanning calorimetry (DSC). Three exothermic peaks were depicted by nonisothermal DSC studies: the first two peaks were attributed to the curing reaction, and the last peak was attributed to the decomposition of the cured epoxy resin. The LC phase transformation of the curing process was observed by PLM. Using AICM, the largest activation energy of the curing reaction of DGEBP/DABP system was obtained as 108 kJ/mol. It can also be learned that LC phase transformation of the curing process affects the reaction significantly.     

Crystallization and Purification of 4,4′-Diaminodiphenyl Ether

The purification of 4,4′-diaminodiphenyl ether (ODA) was investigated. ODA, which contained impurities, was sublimated and anti-solvent (ethanol)-crystallized in N-dimethylformamide (DMF). Fourier transform infrared (FTIR) results revealed that the sublimated crystal was basically identical with the pure ODA sample. The influence of different amounts of ethanol on particle size distribution was analyzed during anti-solvent crystallization. The morphology of the ODA crystal was examined by scanning electron microscopy (SEM). The color of the sample enhanced from a brown powder to a colorless granular crystal. The purity of the sample could be increased from about 30 % to 87 %. With the operations of sublimation and anti-solvent crystallization, the purity, crystal morphology, and particle size distribution of ODA were significantly improved.     

4,4′二氨基二苯醚

一、前言 4,4’二氨基二苯醚别名氧撑二苯胺,简称DADPE。日本1992年产量为200吨,主要生产厂家为歌山精细化学工业公司,产品由日本三井东压公司负责销售,日本年需求量为300吨,其中100吨从美国杜邦化学公司进口,供应日本东丽公司。美国杜邦公司1992年产量为1000吨。DADPE主要是制备聚酰亚胺树脂及共塑制品。我国目前生产有天津     

Effect of the reaction conditions on the properties of poly(4,4′-diphenylether-1,3,4-oxadiazole)s

Summary Poly(4,4-diphenylether-1,3,4-oxadiazole)s have been prepared by polycondensation of 4,4-diphenylether dicarboxylic acid and hydrazine sulphate, HS, in poly(phosphoric acid), PPA, under different reaction condictions. The products were characterized by viscometry, gel permeation chromatography, ¹H-NMR spectrometry and thermogravimetric analysis. Dense membranes have been prepared and submitted to gas transport and wide angle X-ray diffraction, WAXD, experiments. The differences found in permeability and selectivity parameters, as well as in density and WAXD results, are discussed in terms of their solution viscosities and hydrazide repeat unit contents.     

Synthesis of soluble polyarylenes containing alternating 4,4′-(1,1′-binaphthyl) and 4,4′-(3,3′-diphenyl)biphenyl structural units

Summary The synthesis and Ni(0) catalyzed homocoupling polymerization of 4,4-bis[5-(trifluoromethanesulfonyloxy)-2-biphenylyl]-1, 1-binaphthyl (9) are described. This polymerization reaction produces a soluble polyarylene containing alternating 4,4-(1,1-binaphthyl) and 4,4-(3,3-diphenyl)biphenyl structural units.     

Electrosynthesis and protection role of polyaniline–polvinylalcohol composite on stainless steel

Polyaniline–polyvinyl alcohol (PANI–PVA) composite has been electrodeposited on stainless steel surface from aqueous sulfuric acid solution of aniline monomer in presence of soluble PVA at different concentrations. The PVA increased the rate of electropolymerization where 4 g/L PVA formed a composite of 37 wt% PANI and 63 wt% PVA composition. The composite layer exhibited more adhesion to the steel surface in comparison with PANI layer but with less thermal stability. It has higher protection role for the stainless steel (SS) against general and pitting corrosion. It enhanced the passivation of the SS surface by increasing the thickness of oxide film and improving the composition.     

Reaction of CO/CO2 gas mixtures on Ni–YSZ cermet electrodes

The reaction of carbon monoxide/carbon dioxide mixtures on Ni–YSZ cermet electrodes was investigated as a function of the electrode potential and the partial pressures of the reactants at 1273 K. Time-dependent reaction rates are observed for the CO oxidation reaction for oxygen activities corresponding to open circuit potentials in the range from –750 to –1010 mV. The electrode changes between a passive state and several active states for the CO/CO2 reaction. Periodic changes of the reaction rate for the CO oxidation are observed every 30 and 80 s. The impedance spectra recorded at the rest potential and the overpotential dependence of the CO oxidation rate indicate a change in the number of active sites in the reaction zone. In the active state, the CO oxidation reaction is more than one order of magnitude slower than the hydrogen oxidation reaction on these Ni–YSZ cermet electrodes. These results indicate clear differences in the kinetics of the CO and H2 oxidation reaction.     

Poly(4,4′-oxydiphenylene-pyromellitimide)/TiO2 nanocomposites with surface-modified titanium dioxide using 4,4′-methylene diphenyl diisocyanate

This study describes a facile method for preparing poly(4,4′-oxydiphenylene-pyromellitimide) (POPI)/TiO₂ nanocomposites. 4,4′-Methylene diphenyl diisocyanate (MDI) was used as the surface modifier of TiO₂ nanoparticles. MDI-modified and/or unmodified TiO₂ were added to a viscose solution of poly(amic acid) (PAA) prepared by reacting 4,4′-oxydiphenylamine and pyromellitic dianhydride (PMDA). Casting the homogenized mixture onto glass Petri dishes gave the corresponding thermally cured films of POPI/TiO₂ and POPI/TiO₂-MDI nanocomposites through cyclodehydration of the PAA precursor. Diffuse reflectance UV/vis spectroscopy (UV/vis DRS) indicated that two absorption maxima are developed in the spectrum of MDI-treated TiO₂ at about 440 and 580 nm, as well as a slight red shift in the absorption maxima of POPI/TiO₂ and POPI/TiO₂-MDI nanocomposites compared to the neat POPI occurred. From XRD measurements the mean sizes of nano-TiO₂ in TiO₂-MDI, POPI/TiO₂, and POPI/TiO₂-MDI were found to be 27, 22, and 19 nm, respectively. According to the SEM images of POPI/TiO₂ and POPI/TiO₂-MDI nanocomposites, the nano-sized TiO₂ particles with globular shapes were dispersed into the polymer matrix. According to the TGA/DTG thermograms it could be deduced that the incorporation of nano-TiO₂ particles into the polymer matrix can lead to an appreciable thermostability. Taking into account, the DTA thermograms a discrete endothermic transition could be detected at about 290 °C. MDI-grafted TiO₂ seems to be a good candidate for incorporating into poly(4,4′-oxydiphenylene-pyromellitimide) as a commercial type polyimide.     

The polymerization behavior and thermal properties of benzoxazine based on o-allylphenol and 4,4′-diaminodiphenyl methane

Three bifunctional benzoxazines (oAP-ddm, oC-ddm, and P-ddm) were synthesized from 4,4′-diaminodiphenyl methane, formaldehyde, and three phenols, namely o-allylphenol, o-cresol, and phenol. The polymerization temperatures and activation energies of oAP-ddm and oC-ddm are very similar and higher than those of P-ddm; however, their reaction enthalpies exhibit inverse behavior. The storage moduli of the corresponding polybenzoxazines, PoAP-ddm, PoC-ddm, and PP-ddm, are approximately 2.1, 3.2, and 2.9 GPa at 25 °C, respectively, and their glass transition temperatures are 139, 166, and 198 °C, respectively. The thermal stabilities of PoAP-ddm and PoC-ddm are similar and lower than that of PP-ddm. The results indicate that polybenzoxazines based on ortho-substituted phenols provide higher flexibility than their counterparts prepared from unsubstituted phenol.     

Synthesis of 3,3′-dimethyl-4,4′-diaminodiphenylmethane catalyzed by zeolites replacing mineral acids

Synthesis of 3,3′-dimethyl-4,4′-diaminodiphenylmethane (MDT) from o-tolylamine and formaldehyde over zeolites was investigated. Among the three tested zeolites, Hβ showed higher catalytic activity than HY and HZSM-5 for MDT synthesis. In the case of Hβ as a catalyst, the effects of feed composition, reaction time and temperature on the yield and selectivity of product MDT were further examined to optimize process conditions. In an o-tolylamine:formaldehyde = 8:1 molar ratio, the two-step reaction running at 413 K for 0.5 h and then 433 K for 0.5 h gave the MDT yield of 87.5%.     

Novel interpenetrating and non-interpenetrating structures based on semi-rigid 4,4′-biphenyl-based ligand

The reactions of semi-rigid bidentate ligand 4,4′-bis(benzimidazol-1-ylmethyl)biphenyl (bbmb) with NiCl₂ and CuCl₂ and Cd(OAc)₂ afford novel complexes {[M(bbmb)₂(Cl)(OH)](H₂O)₂}_n (M = Ni(1), Cu(2)) and [Cd₂(OAc)₄(bbmb)₃]₂(CH₃OH)₃(H₂O)₂ (3). Both complexes 1 and 2 feature parallel 2-fold interpenetrating (4,4)-windmill-like layer morphology. Complex 3 presents unique discrete quad-nuclear motif comprised by two couples of alternating single and double twisting chains. The three complexes exhibit active second-order NLO effects.     

Two-dimensional assembling of 4,4′-bipyridine and 4,4′-azopyridine bridged iron (II) linear coordination polymers via hydrogen bond

Novel two-dimensional polymers, [Fe(L¹)(H₂O)₂(NCX)₂] · L¹ (L¹ = 4,4′-bipyridine (bipy)) (1, 2) and [Fe(L²)(CH₃OH)₂-(NCX)₂] · L² (L² = 4,4′-azopyridine (azpy)) (3) and X = S (1,3),Se (2), have been synthesized and characterized by X-ray crystallography. The structures reveal the formation of trans-L-bridged [Fe(NCX)₂(Y)₂] where Y = H₂O, CH₃OH linear chains assembled into two-dimensional networks by hydrogen bonds between the uncoordinated ligand L and the coordinated solvent molecules.     

Pervaporation of water/acetic acid through polyimide membranes from 3,3′, 4,4′-benzophenone tetracarboxylic dianhydride and 4,4′-oxydianiline

Summary Pervaporation performance of polyimide (PI) membrane from 3,3, 4,4-benzophenone tetracarboxylic dianhydride (BTDA) and 4,4-oxydianiline (ODA) was investigated at 80wt% feed acetic acid concentration and at 65°C. Imide contents in PI film were estimated by thermogravimetric analysis (TGA) method. The separation factor of PI membrane increases with the degree of imidization, while the flux was almost constant. The separation factor toward water through PI-94 membrane was about 417 with the flux of 47 g/m². hr measured at 65°C and with 80wt% acetic acid as a feed. PI-94 showed the best pervaporation performance toward the separation of water from acetic acid solution among the PI membranes investigated. The swelling behaviors at various feed concenration were also examined.     

A 2D polymer constructed through bridging oxalato and 4,4′-bipyridine ligands: crystal structure and magnetic behavior of [Cu3(μ-ox)3(μ-4,4′-bpy)2(4,4′-bpy)2]n

The crystal structure of the compound [Cu₃(μ-ox)₃(μ-4,4^′-bpy)₂(4,4^′-bpy)₂]_n 1 (ox=oxalato, 4,4^′-bpy=4,4^′-bipyridine) is comprised of two-dimensional sheets in which copper(II)–oxalato chains are cross-linked by bridging bidentate 4,4^′-bpy ligands. Metal centers show a tetragonally elongated octahedral environment formed by four oxygen atoms from two asymmetrically coordinated oxalato ligands and two nitrogen atoms from two trans-coordinated 4,4^′-bpy molecules. The magnetic measurements show the occurrence of weak ferromagnetic couplings.     

4,4′-二氨基二苯砜

【王严情沉】 日本和歌山厂年生产4,4尸一二氨基二苯矾30~40吨。【简称】4,4‘一nDS 【性状】白色柱状结晶,熔点1油~179℃,在空气中的热稳定性好,从280℃开始慢慢分解。比热1 .98焦耳/克·度〔100℃),微溶于水(0 .08克/100克,50℃),可溶于乙醇、三氯甲烷、乙腊及其它质子惰性极性有机溶剂等,也溶于稀矿酸。 【市销产品规格】 外观:淡黄白色粉末 比重:1.33 熔点:>176℃ 纯度:>99% 水分:<0.15% 灰分:<0.注% t制法】以对一硝基氯苯或氯苯为原料,照下述方法合成: (1)使硫化钠与对一硝基氯苯反应,生成二稍基二苯硫醚,氧化后则生成二硝基二苯枫,…     

The effect of tertiary amines on the network formation of bisphenol-A diglycidyl ether in reaction with 4,4′-diaminodiphenyl methane

Summary The structure-property relationships of crosslinking systems consisting of bisphenol-A diglycidyl ether and 4,4-diaminodiphenyl methane were investigated by following the network formation and characterization of cured samples in dependence on the molar ratio and on the curing temperature. Gelation times, soluble parts and glass transition temperatures of the cured systems were determined. The influence of N,N-dimethylbenzylamine as an accelerator was discussed.     

Investigation of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone-based catalyst in the reaction of liquid-phase oxidation of inorganic sulfides

In this paper, the intermediate and final reaction products of catalytic oxidation of inorganic sulfides in the presence of oxygen dissolved in the kerosene fraction and 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone were investigated. The thiosulfate and sulfate are major products of the oxidation of sodium sulfide under these conditions. The intermediate and final products in the catalytic oxidation of sulfide sulfur do not affect the rate of its oxidation. The yield of catalytic oxidation products depends on the nature of the sulfide and on the pH of the solution. The catalytic cycle for sulfide oxidation in the presence of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone is shown. The role of 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone is to create a new and a more effective way of electron transfer from the reducing agent (sulfide) to the oxidant (oxygen).     

Synthesis,characterization and crystal structure of one Mn(II) complex with 4,4′-bisimidazolylbiphenyl and 4,4′-sulfonyldibenzoic acid

One new title compound [Mn₃(BIBP)(sdb)(NO₂⁻)₂(H₂O)₂]_n·2DMF (1) (BIBP = 4,4′-bisimidazolylbiphenyl, sdb = 4,4′-sulfonyldibenzoic acid) has been synthesized under hydrothermal condition. The title compound was characterized by IR spectra, thermal analysis, single crystal and powder X-ray diffraction. Magnetic susceptibility measurements indicate that compound 1 exhibits antiferromagnetic coupling interaction.     

Effect of chemical structure of aromatic dianhydrides on the thermal, mechanical and electrical properties of their terpolyimides with 4,4′-oxydianiline

Aromatic terpolyimides were synthesized by the reaction of 3,3′,4,4′-oxydiphthalicdianhydride(ODPA), 3,3′,4,4′-biphenyldianhydride(BPDA) and 3,3′,4,4′-benzophenonetetracaboxylicdianhydride(BTDA) with 4,4′-oxydianiline(ODA) via thermal imidization with the view to enhance their tensile properties without compromising thermal properties compared to their homo and copolyimides. Their films were characterized by FTIR, TGA, DSC and XRD. Their FTIR spectra established formation of polyimide by the characteristic vibrations at 1375cm⁻¹(C-N stretch) and 1113 cm⁻¹(imide ring deformation). TGA results showed imidization of residual polyamide acid close to 250 °C and decomposition of polyimides at about 540 °C. XRD results showed amorphous nature for all terpolyimides. Their tensile strength and tensile modulus were higher than either homo or copolyimides. Incorporation of BPDA, without bridging groups between the aromatic rings into the backbone of ODPA/BTDA-ODA is suggested as the cause for such an enhancement. Such terpolyimide can find application as adhesives in making flexible single/multilayer polyimide metal-clad laminates in flexible printed circuits and tape automated bonding applications. In addition, the terpolyimide, BPDA/BTDA/ODPA-ODA (mole ratio 0.5:0.25:0.25:1), showed low dielectric constant (3.52) as BPDA could offer slight rigidity by which the orientation of polar groupings could be reduced.