Ring‐opening metathesis polymerization of bicyclo[2.2.1]hepta‐2,5‐diene (norbornadiene) initiated by new ruthenium(II) complex

The polymerization of norbornadiene (NBD) initiated by a novel ruthenium (Ru)(II) complex ( 3 ) containing 1,1′‐pyridine‐2,6‐diylbis[3‐(dimethylamino)prop‐2‐en‐1‐one] ( 1 ) as ligand has been investigated. Ru complexes exhibit more catalytic activity in the ring‐opening metathesis polymerization (ROMP) of NBD when activated with trimethylsilyldiazomethane (TMSD). The influence of the various experimental parameters such as reaction time and temperature, nature of the solvent and catalyst, ratio of the NBD/Ru, and TMSD addition has been investigated. The polymers have been obtained in high yields with a relatively low polydispersity index for ROMP and a high $ \bar M_n $ and $ \bar M_w $ values in a monomodal distribution. Their structures have been determined by means of FTIR and ¹H‐NMR spectroscopy. Thermal properties have been determined via thermogravimetric analysis and DTG methods. The NBD polymerization results that initiated by Ru‐based catalyst coordinated to amine ligand have been compared to initiated by [RuCl₂(p‐cymene)]₂. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Adsorption studies on the treatment of textile dyeing effluent by activated carbon prepared from olive stone by ZnCl2 activation

This study aimed to investigate the removal of a reactive dye from aqueous solution by adsorption. Activated carbon prepared from olive stone, an agricultural solid by-product, was used as adsorbent. Different amounts of activating agent (ZnCl₂) and adsorbent particle size were studied to optimise adsorbent surface area. The adsorption experiments were conducted at different process parameters such as adsorbent dose, temperature, equilibrium time and pH. The experimental results showed that at equilibrium time 120 min, optimum pH ranged between 3 and 4, and adsorbent dosage was 2.0 g 200 ml⁻¹. While the kinetic data support pseudo-second order, a pseudo-first order model shows very poor fit. Adsorption isotherms were obtained at three different temperatures (288, 298 and 308 K). The fitness of adsorption data to the Langmuir and Freundlich isotherms was investigated. In addition, the thermodynamic parameters such as isosteric enthalpy of adsorption (Δ H _ads) _y , isosteric entropy of adsorption (Δ S _ads) _y and free energy of adsorption Δ G ⁰_ads were calculated. BET surface area measurements were made to reveal the adsorptive characteristics of the produced active carbon. The surface area of the activated carbon produced with 20% w/w ZnCl₂ solution was 790.25 m² g⁻¹.     

1,4-Dithiaheterocycle-fused porphyrazines: Synthesis,characterization, voltammetric and spectroelectrochemical properties

Porphyrazines (M = H, Mg, Zn and Co) with a 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin group fused to each pyrrole unit were synthesized and characterized starting with the corresponding unsaturated dicarbonitrile derivative. The voltammetric and spectroelectrochemical characterizations of the metallo-porphyrazines (M = 2H⁺, Mg²⁺, Zn²⁺ and Co²⁺) substituted with 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin groups on peripheral positions are described. Cyclic voltammetry and differential pulse voltammetry studies showed that while metal-free, magnesium, and zinc porphyrazines represented well-defined one-electron ligand-based reductions and ligand-based one-electron oxidation couples, cobalt porphyrazine gave both metal-based and ligand-based reduction and oxidation couples. Assignments of the redox couples were confirmed by spectroelectrochemical measurements.     

Synthesis of 1,1′-ferrocene bis(carboxypyrazole) compounds and displacement of the pyrazole ligands

The reaction of 1,1′-ferrocenedicarbonyl chloride with pyrazole or 3,5-dimethyl pyrazole generates novel 1,1′-ferrocene bis(amide) compounds 1 and 2, respectively. The crystal structure of 1 shows that the pyrazole rings are essentially co-planar with each other and with the cyclopentadienyl rings. Attempts to use the complexes as a chelating ligand were unsuccessful. Instead, treatment of 1 or 2 with Mo(CO)₄(pip)₂, pip = piperidine, led to displacement of the pyrazole ligands and formation of the known amide compound, 1,1′-ferrocene bis carbonyl piperidine. Replacement of the pyrazole is ascribed to the weakness of the amide bond caused by the aromaticity of the pyrazole ring. Crystal data for C₁₈H₁₄FeN₄O₂ (1): monoclinic P2(1)/c, a = 13.3907(18) Å, b = 10.2112(14) Å, c = 11.3082(16) Å, β = 105.209(2)°, V = 1492.1(4) Å³, Z = 4.     

Novel composite polymer electrolyte membranes based on poly(vinyl phosphonic acid) and poly (5‐(methacrylamido)tetrazole)

Heterocyclic molecules are generally used in the proton conducting membranes as dopant or polymer side group due to their high proton transfer ability. Composite proton conducting membranes based on poly(vinylphosphonic acid) (PVPA) and poly(5‐(methacrylamido)tetrazole) (PMTet) were produced. The homopolymers, prepared from their corresponding monomers, were blended at several mol ratios to obtain the polymer electrolyte membranes. All samples were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differantial scanning calorimetry (DSC), cyclic voltammetry (CV), and impedance analysis. Besides, the morphology of the membranes was studied by X‐ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). FTIR spectra confirmed the formation of hydrogen bonding network between PVPA and PMTet units. TGA showed that the polymer electrolyte membranes were thermally stable up to ～210°C. CV curves demonstrated the oxidative stability of the samples in 3 V region. In anhydrous conditions, the maximum proton conductivity was determined as 0.06 Scm^?1 at 150°C for PMTetP(VPA)₄. POLYM. ENG. SCI., 55:260–269, 2015. © 2014 Society of Plastics Engineers     

Hardness and Wear Behaviours of Al Matrix Composites and Hybrid Composites Reinforced with B4C and SiC

Powder Metallurgy and Metal Ceramics - The conversion into the desired shape of the metal powders using Powder Metallurgy (PM) method enables economically mass productions. This case allows...     

A green approach for the preparation of nanostructured zinc oxide: Characterization and promising antibacterial behaviour

In the present study, nanostructured zinc oxide (ZnO) films have been successfully synthesized using fruit extract of Viburnum opulus L. (VO) on glass slides by successive ionic layer adsorption and reaction (SILAR) procedure. The impact of VO concentrations on the structural, morphological, optical, electrical, and antibacterial attributes of ZnO films has been investigated in detail. The samples' XRD patterns present a hexagonal crystal structure with a preferential orientation along the (002) plane. The crystallite size values of ZnO samples were found to be in the ranges from 14.88 to 9.23 nm. The supplementation of VO to the synthesis solution remarkably affected the surface morphological features of the ZnO films. The optical results demonstrated that band gap energy values of the ZnO films at room temperature were decreased from 3.20 to 3.07 eV as a function of VO content in the bath solution. The films' electrical properties were determined by impedance analysis in the frequency range of 20 Hz ?1 MHz. Impedance-frequency measurements showed VO insertion to ZnO thin films cause an increase in impedance value at the low frequencies. Cole-Cole plots with a single semi-circle confirmed the contribution of grain and grain boundary for the electrical conduction process. The agar disk diffusion method was used to test the antibacterial properties of ZnO/VO inserted ZnO and inhibition zones were measured. VO inserted ZnO showed a stronger inhibitory effect on gram-positive bacteria Staphylococcus aureus (ATCC 25923) and gram-negative bacteria Escherichia coli (ATCC 35218) than ampicillin antibiotic used as a control group. In line with the promising bactericidal results of a new generation, VO inserted ZnO, the nanostructured product with this study, it can also be applied in multidrug-resistant clinical isolates obtained from patients.