Miscibility behaviour of sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) copolymers in the blends with poly(styrene-co-maleic anhydride) and with poly(α-methylstyrene-co-maleic anhydride)

Summary The miscibility behaviour of sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) of the different degree of sulfonylation blended with poly(styrene-co-maleic anhydride) or poly(-methylstyrene-co-maleic anhydride) was studied. The critical degree of sulfonylation for phase separation in these blends was found to be 55 mole % and 66 mole %, respectively. The miscibility behaviour was analyzed on the basis of the mean field treatment and studied by DSC.Dedicated to Professor Dragutin Fle in honor of his 70th birthday     

FTIR and NMR characterization of thermosetting methyl methacrylate terminated poly(2,6-dimethyl-1,4-phenylene oxide)—triallyl isocyanurate copolymer

Journal of Polymer Research - The removal of sulfur-containing compounds from the fuel using the pervaporation method is an innovation that has made possible by using membrane based technologies....     

The role of zinc oxide in Cu/ZnO catalysts for methanol synthesis and the water–gas shift reaction

All commercial catalysts for methanol synthesis and for the water–gas shift reaction in the low temperature region contain zinc oxide in addition to the main active component, copper. The varied benefits of zinc oxide are analysed here. The formation of zincian malachite and other copper/zinc hydroxy carbonates is essential in the production of small, stable copper crystallites in the final catalyst. Further, the regular distribution of copper crystallites on the zinc oxide phase ensures long catalyst life. Zinc oxide also increases catalyst life in the water–gas shift process by absorbing sulphur poisons but it is not effective against chloride poisons. In methanol synthesis, zinc oxide (as a base) removes acidic sites on the alumina phase which would otherwise convert methanol to dimethyl ether. Although bulk reduction of zinc oxide to metallic zinc does not take place, reduction to copper–zinc alloy (brass) can occur, sometimes as a surface phase only. A new interpretation of conflicting measurements of adsorbed oxygen on the copper surfaces of methanol synthesis catalysts is based on the formation of Cu–O–Zn sites, in addition to oxygen adsorbed on copper alone. The possible role of zinc oxide as well as copper in the mechanisms of methanol synthesis is still the subject of controversy. It is proposed that, only under conditions of deficiency of adsorbed hydrogen on the copper phase, hydrogen dissociation on zinc oxide, followed by hydrogen spillover to copper, is significant. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of poly(2,6-dimethyl-1,4-phenylene ether) with controlled molecular weight via suspension polymerization catalyzed by amine–copper (I) complexes under various reaction conditions

The oxidative suspension polymerization of 2,6-dimethyl phenol (DMP) to poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was performed with the use of emulsifier in water–chloroform biphasic medium. The effects of DMP/catalyst mole ratio, ligands, emulsifiers, and 2,4,6-trimethyl phenol on polymerization were investigated in terms of molecular weight and yield. Various ligands were employed in the polymerization to investigate ligand efficiency. Intrinsic viscosity measurement data showed that the most efficient ligand was 1-methyl imidazole (Meim) in terms of molecular weight. By incorporating different amount of DMP in the monomer feed, it was possible to control the molecular weight of PPE in the oxidative suspension polymerization.     

Polystyrene–poly(ethylene oxide) diblock copolymers micelles in water

Micellization in water of polystyrene–poly(ethylene oxide) diblock copolymers is achieved by the stepwise dialysis technique in order to prepare micellar solutions for copolymers with a wide range of molecular parameters. Hydrodynamic radii, determined by quasielastic light scattering, are correlated with the molecular parameters, e.g. molecular weight and composition, and compared with the theory. Two couples of phenanthrene and anthracene labelled copolymers are used to prepare micellar solutions by mixing them before and after dialysis. The non radiative energy transfer is determined on these solutions to prove that polystyrene-poly(ethylene oxide) diblock copolymers micelles in water are "frozen" micelles even when heated near the Tg of polystyrene. Received: 3 November 1997/Revised version: 1 December 1997/Accepted: 2 December 1997     

Cationic palladium(II)–acetylacetonate complexes bearing α-diimine ligands as catalysts in norbornene polymerization

A variety of palladium(II)–acetylacetonate complexes bearing α-diimine ligands were synthesized by the reaction of [Pd(acac)(MeCN)₂]BF₄ with N⁀N ligands. When activated with BF₃·OEt₂, these complexes provide access to a new class of alkylating agent free Pd–diimine catalyst systems. Catalyst screening for the vinyl addition polymerization of norbornene showed their high activities of 10²–10⁴ kg_pol mol_cat^− 1 h^− 1.     

Novel metal oxide nanocomposite of Au/CuO–ZnO for recyclable catalytic aerobic oxidation of alcohols in water

CuO–ZnO supported gold nanoparticle is introduced as a new, efficient, and recyclable catalyst for the aerobic oxidation of alcohols. The CuO–ZnO support was prepared by co-precipitation and Au nanoparticles were loaded on support by a deposition–precipitation method. The catalyst was characterized by XRD, BET surface area, FESEM, EDS and HRTEM techniques. A wide range of alcohols, including benzylic, primary and secondary alcohols are converted into the corresponding carbonyl derivatives. The experimental procedure with Au/CuO–ZnO catalyst is quite straightforward and the catalyst is recyclable up to 6 consecutive runs by simple filtration.     

Modification of poly(vinylidene fluoride) membranes with aluminum oxide nanowires and graphene oxide nanosheets for oil–water separation

To improve the hydrophilic and oleophobic properties of membrane, we adopted aluminum oxide (Al₂O₃) nanowires and graphene oxide (GO) nanosheets to modify poly(vinylidene fluoride) (PVDF) membranes. The experimental results show that the intercalation of Al₂O₃ nanowires between GO nanosheets effectively improved the roughness of the GO–Al₂O₃–PVDF membrane, and the permeability of the membrane with an optimal mass ratio of Al₂O₃ to GO of 7.5 was 31 times that of the GO–PVDF membrane. Furthermore, the addition of Al₂O₃ nanowires significantly enhanced both the hydrophilic and oleophobic properties of the GO–Al₂O₃–PVDF membrane. On the basis of the extended Derjaguin–Landau–Verwey–Overbeek theory, the energy barriers between the oil droplets and GO–PVDF and GO–Al₂O₃–PVDF membranes were 0.63 and 0.9 KT, respectively; this indicated improvements in the anti-oil-fouling ability of the GO–Al₂O₃–PVDF membranes. We also found that both the GO–PVDF and GO–Al₂O₃–PVDF membranes had great oil–water separation rates (97.9 and 99.4%, respectively) with an initial oil concentration of 200 mg/L. The findings of this study show that the GO–Al₂O₃–PVDF membrane is a promising oil–water separation membrane, and further investigation of the cleaning procedure is needed to promote its practical application in oil–water separation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47493.     

Studies on electrochemical properties of poly (ethylene oxide)-based gel polymer electrolytes with the effect of chitosan for lithium–sulfur batteries

Composite gel polymer electrolytes (CGPE), with different proportions of poly (ethylene oxide), plasticizers namely 1,3-dioxolane (DIOX)/tetraethelyneglygol dimethylether (TEGDME) and a lithium salt (LITFSI) with the addition of filler chitosan were prepared using the solution casting technique in an argon atmosphere. The membranes were subjected to various characterization techniques such as TG/DTA, FTIR and an ac impedance analysis. A lithium symmetric cell (Li/CGPE/Li) was assembled and the interfacial stability of the polymer electrolyte with a lithium anode was measured. The electrochemical stability and the transport properties of the high conducting sample were also measured. TG/DTA shows the thermal stability of the high conducting sample. The optimal value of the plasticizers was to be found in the ionic conductivity point of view.     

Effect of silicone dioxide and poly(ethylene glycol) on the conductivity and relaxation dynamics of poly(ethylene oxide)–silver triflate solid polymer electrolyte

The conducting and relaxation dynamics of Ag⁺ ions in poly(ethylene oxide) (PEO)–silver triflate (AgCF₃SO₃) solid polymer electrolytes (SPEs) containing nanosize SiO₂ filler and poly(ethylene glycol) (PEG) as a plasticizer were studied in the frequency range 10 Hz to 10 MHz and in the temperature range 303–328 K. The comparatively lower conductivity of the plasticized (PEG) PEO–AgCF₃SO₃–SiO₂ nanocomposite electrolyte system was examined by analysis of the Fourier transform infrared (FTIR) spectroscopy and conductivity data. The electric modulus (M″) properties of the SPE systems were investigated. A shift of the M″ peak spectra with frequency was found to depend on the translation ion dynamics and the conductivity relaxation of the mobile ions. The value of the conductivity relaxation time was observed to be lower for the PEO–AgCF₃SO₃ system only with nanofiller SiO₂. The scaling behavior of the M″ spectra showed that the dynamical relaxation processes was temperature-independent in the PEO–AgCF₃SO₃ and PEO–AgCF₃SO₃–SiO₂–PEG polymer systems, whereas they were temperature-dependent for the PEO–AgCF₃SO₃–SiO₂ system. However, the relaxation processes of all of theses systems were found to be dependent on their respective compositions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

One-pot synthesis of two new metal–organic networks: hydrogen bonded mononuclear Cu(II) complex and mixed-valence Cu(I,II) coordination polymer with encapsulated 14-membered unique water cluster

{[Cu₄(μ-bpe)₄Cu₂(μ-pydc)₂(μ₃-pydc)₂]·14H₂O}_n (1) and [Cu(pydcH)₂(bpe)₂] (2) have been solvothermally synthesized by 1,2-bis(4-pyridyl)ethylene (bpe) along with dianionic pyridine-2,3-dicarboxylate (pydc) ligands and characterized by elemental, FT-IR and thermal analyses techniques. In the solvothermal synthesis of complexes, 1 was isolated when the reactor was opened whereas 2 was crystallized after 3 weeks. The X-ray crystallographic studies show that complex 1 exhibits ladder-like structure involving mixed-valence Cu(I,II) which has generated a simultaneous in situ redox reaction and a unique 14-membered water cluster consisting of an eight-membered open-cube hexamer and two cyclic water trimers has been observed in hydrophilic cavities of 1. Supramolecular network of 2, which has proton transfer product of pydcH cations, is formed by O–H···N and aromatic interactions.     

Catalytic performance of perovskite-like oxide doped cerium(La_(2-x)Ce_xCoO_(4±y)) as catalysts for dry reforming of methane

A series of oxides(La_(2-x)Ce_xCoO_(4±y)) with perovskite-like structure were prepared by the Pechini sol–gel method for dry reforming of methane reaction(DRM). The prepared catalysts were characterized by BET, XRD,TGA, H_2-TPR and SEM. Experimental results indicate that the addition of Ce can impact both sample morphology and catalytic performance significantly compared with La_2CoO_4 catalyst, and LaCeCoO_4 presented the highest catalytic ability among all the samples. The Ce addition tends to increase the specific surface area of La_(2-x)Ce_xCoO_(4±y)from 0.2 to 8.5 m~2·g~(-1), suggesting that LaCeCoO_4 catalyst contained more well-dispersed active sites and more space to reaction. Moreover, the catalytic performance and anti-coking ability were substantially improved after Ce addition during DRM, which may be attributed to the decrease of LaCoO_3 particle size and growth of oxygen storage capacity, respectively.     

Amino-salicylaldimine–palladium(II) complexes: New and efficient catalysts for Suzuki and Heck reactions

A series of amino-salicylaldimine–palladium(II) complexes bearing 5-methyl-3-(R-1-ylmethyl)-salicylaldimine ligands (R = morpholine, piperidine, pyrrolidine, 4-methylpiperazin, diisopropylamine) have been prepared and characterized by IR, ¹H NMR and elemental analysis. Crystal structure details of complex 2b have been confirmed by X-ray structure analysis. The obtained Pd(II) complexes were found to be effective catalysts for the Suzuki and Heck cross-coupling reactions which could be carried out in the undried solvent under air.     

D–A–D-structured conducting polymer-modified electrodes for detection of lead(II) ions in water

Donor–acceptor–donor-structured thiophene derivative-based conducting polymer poly(7,9-dithiophene-2yl-8H-cyclopenta[a]acenaphthalene-8-one) was chemically synthesized. This polymer was used to modify both glassy-carbon and carbon-paste electrode, which was used to detect lead(II) ions present in water in the range of 1 mM to 0.1 μM. Cyclic voltammetry confirms the formation of the co-ordination complex between the soft segment of polymer and the dissolved lead ion. Anodic stripping voltammetry was carried out by the modified electrode to determine the lower limit of detection of dissolved lead(II) species in the solution. Differential adsorptive stripping and impedance measurements were also conducted to find the lowest possible response of the as-synthesized polymer to lead(II) ion in water. The electrochemical performance of the modified electrodes at different pH (4, 7 and 9) environments was carried out by stripping voltammetry, to get optimum sensitivity and stability under these conditions. Finally, interference analysis was carried out to detect the modified electrode’s sensitivity towards lead ion affinity in water.     

Ni(II)–Mg(II)–Al(III) catalysts for hydrogen production from ethanol steam reforming: Influence of the activation treatments

The effect of the Ni(II)–Mg(II)–Al(III) layered double hydroxide (LDH) activation conditions over the surface and bulk composition and the catalytic performance in ethanol steam reforming (ESR) is studied. Ternary oxides were prepared by thermal decomposition of LDHs synthesized using the homogeneous precipitation method with urea. Catalyst precursor is submitted to two different activation treatments: calcinations at 400, 500, 600 and 700 °C with subsequent reduction at 720 °C, or direct reduction at 720 °C. The samples were characterized by sorptometry, H₂ chemisorption, ICP chemical analysis, thermogravimetric analysis, X-ray diffraction, X-ray photoelectronic spectroscopy and temperature programming reduction. The catalysts obtained by calcination at 600 °C and then reduction at 720 °C and those directly reduced at 720 °C showed the better performance in ESR. The precursor submitted to a proper thermal treatment develops, through a decoration-demixing process, a Ni(II)-poor spinel-type shell onto NiO domains.     

Mechanical milling of thermoresponsive poly(N-isopropylacrylamide) hydrogel for particle-oriented oil–water separation

The separation of oil and water is widely studied because of the promise of cleaning up oil spills. One pathway is with thermosensitive polymer-based hydrogels. As hydrogels are raised to the lower critical solution temperature (LCST), they undergo a change of state, from hydrophilic to hydrophobic. Oil–water separation using hydrogels in particle form that are responsive to external stimuli (e.g., magnetic field and temperature) are of great interest. This work uses a novel approach of ball milling dry hydrogel into different sizes and testing oil–water separation efficacy. This study investigated the potential for ball milling P(NIPAAm) bulk hydrogel into small particles size ranges (0–45, 45–90, 90–106, 106–150, and 150+ μm) and the resulting impact on oil–water separation. It was observed that the LCST for the p(NIPAAm) in gel form was 32 °C while increasing to ~40 °C for the powdered form. It was found that the hydrogel particles of different size ranges managed to capture 196, 207, 208, 162, and 124% of its weight in oil, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48771.     

Effects of the preparation methods on the performance of the Cu–Cr–Fe/γ-Al2O3 catalysts for the synthesis of 2-methylpiperazine

Co-precipitation, impregnation and ultrasonic sol–gel (USG) methods have been used to prepare Cu–Cr–Fe/γ-Al₂O₃ catalysts, which were further used to synthesize 2-methylpiperazine. The catalysts were characterized by XRD, XPS, TG/DSC, BET, TPR, AAS and TEM. It is found that preparation method can greatly impact the catalytic performance of the catalysts, the Cu–Cr–Fe/γ-Al₂O₃ catalyst prepared by the ultrasonic sol–gel method proved to be the most active and stable for this reaction. The dispersion and stabilization of Cu⁰ in the reduced catalysts are attributed to the existence of CuCr₂O₄ and Fe₂O₃. A surprising copper migration was detected by XPS analysis for the Cu–Cr–Fe/γ-Al₂O₃-USG catalyst after the calcination process, which may be crucial to the high activity and stability of this catalyst.     

CuO–CeO2 mixed oxide catalysts for the selective oxidation of carbon monoxide in excess hydrogen

A series of mixed oxide CuO–CeO₂ catalysts were prepared by coprecipitation and tested for the selective oxidation of carbon monoxide in the presence of excess hydrogen. These catalysts were found to be very active and exceptionally selective for this reaction and exhibited a good resistance towards CO₂ and H₂O. The catalytic performance of these non-noble metal containing catalysts is compared with that of other selective CO oxidation catalysts reported in literature.