Sulfonated Aromatic Polymers and Organically Modified Montmorillonite Nanocomposite Membranes for Fuel Cells Applications

Aromatic polymers, such as sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), sulfonated poly(ether ether ketone) (SPEEK), and sulfonated poly(ether sulfone) (SPES), at the optimum degrees of sulfonation (DS), are suggested and evaluated as alternatives to Nafion for direct methanol fuel cells (DMFCs) applications. To reduce the methanol cross-over, which decreases the efficiency of the cell, organically modified montmorillonite nanoclays (OMMT) were added at 1 wt% to the sulfonated matrices with the optimum DS. The X-ray diffraction (XRD) patterns of nanocomposite membranes proved that the nanoclay layers were exfoliated. The proton conductivity and methanol permeability of the membranes, as well as the ion-exchange capacity (IEC), were measured. The selectivity parameter, ratio of proton conductivity to methanol permeability, was identified at 25°C for the nanocomposite membranes and the results were compared with Nafion117. Finally, the DMFC performance tests were investigated at 70°C and 5 M methanol feed for the manufactured nanocomposite polyelectrolyte membranes (PEMs). The SPEEK-based nanocomposite membrane showed the highest maximum power density in comparison with Nafion 117 and SPES and SPPO nanocomposite membranes. The results indicated that the nanocomposite membranes were promising PEMs for DMFC applications.     

Bell Inequalities and Separability of Uncommon Causes from the Setup Configuration

In the present paper the integration region Λ with more than one hidden variable is attributed to a pair of particles in the Bell's thought experiment as the local causal events in their common lightcone. Moreover, the possibility of uncommon causal events influencing the spin measurement is not ignored. Then, with regard to the separability of the influence of the uncommon events from configuration of the setup, and by relying on local realism and coherency, each of the Bell's inequality versions is obtained by measuring spin in three and four different directions. PACS numbers: 03.65.Ud 03.65.Ta.     

Metal‐stabilized rare tautomers: N4 metalated cytosine (M = Li+, Na+, K+, Rb+ and Cs+), theoretical views

Ab initio calculations indicate that metalation of the exocyclic amino group of cytosine by the elements of Group IA (Li, Na, K, Rb and Cs) induces protonation of a nucleobase ring nitrogen atom, and hence causes a proton shift from an exocyclic to an endocyclic nitrogen atom. Thus, this metal‐assisted process leads to the generation of rare nucleobase tautomers. The calculations suggest that this kind of metalation increases the protonation energies of the aromatic ring of the nucleobase. The present study reports the quantum chemistry analysis of the metal‐assisted tautomerization. The calculations clearly demonstrate that metalation of the exocyclic amino group of the nucleobase significantly increases the protonation energy of the aromatic rings of the nucleobase. Also, absolute anisotropy shift, molecular orbital and natural bond orbital calculations are compatible with these results. Copyright © 2003 John Wiley & Sons, Ltd.     

Novel Triplet Ground State Silylenes: H–N = C = Si, CN–N = C = Si, and MeO–N = C = Si at DFT Levels

Summary.  DFT calculations predict the existence of three new triplet ground state silylenes: [(imino)-methylene]silylene, [(cyanoimino)methylene]silylene, and [(methoxyimino)methylene]silylene, with CNSiX formula (X = H, CN, and OMe, respectively). Discrepancies are found between DFT and some ab initio results.     

A green and efficient synthesis of isoxazol-5(4<Emphasis Type="Italic">H</Emphasis>)-one derivatives in water and a DFT study

A series of 4-arylmethylene-3-methylisoxazol-5(4H)-one derivatives are obtained via treating ethyl acetoacetate, hydroxylamine hydrochloride and variety of aromatic aldehyde compounds in the presence of antimony trichloride as an efficient catalyst in aqueous media. Mild conditions, safe, short reaction times, commercially available catalyst, environmentally friendly, no uses of organic solvent and high yields are remarkable advantages to this process. (Z)-4-(3-hydroxybenzylidene)-3-methylisoxazol-5(4H)-one, (HBIM), is characterized by theoretical (density functional theory) and experimental (IR, ¹H NMR, CV and UV). The structural parameters, vibrational frequencies, molecular electrostatic potential, frontier molecular orbital analysis (HOMO–LUMO), thermodynamic properties and nonlinear optical properties are found and discussed. UV–Vis spectra are recorded in two organic solvents. Thermal stability of HBIM is studied by thermogravimetric analysis. The molecule orbital contributions are studied using the total and partial density of states (TDOS and PDOS).     

A facile synthesis of boron nanostructures and investigation of their catalytic activity for thermal decomposition of ammonium perchlorate particles

In this research, ultrasound irradiation as a simple method was used to produce boron nanostructures. Reaction conditions such as boron concentration and sonication time show important roles in the size, morphology and growth process of the final products. The boron nanostructures (nanoparticles and nanorods) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, small-angle X-ray scattering and inductively coupled plasma atomic emission spectroscopy techniques. Primary evaluation of results showed that nanoparticles and nanorods of boron successfully have been prepared with 25–40 and 50–100 nm average particle size, respectively. These nanostructures (nanoparticles and nanorods) were studied as an additive for promoting the thermal decomposition of ammonium perchlorate (AP) particles. Thermochemical decomposition behaviors of treated samples were characterized by thermal gravimetric analysis and differential scanning calorimetry techniques. Also, the kinetic parameters of thermal decomposition processes of pure and treated samples were obtained by nonisothermal methods proposed by Kissinger and Ozawa. However, boron nanoparticles with the smallest average particle size (25–40 nm) have the most significant catalytic effect including the decrease in decomposition temperature of AP + B nanocomposite by 100 °C, increase in the heat of decomposition from 580 to 1354 J g^?1 and decrease in activation energy from 207 to 110 kJ mol^?1.     

Mathematical modelling for extraction of oil from Dracocephalum kotschyi seeds in supercritical carbon dioxide

Extraction of oil from Dracocephalum kotschyi Boiss seeds using supercritical carbon dioxide was designed using central composite design to evaluate the effect of various operating parameters including pressure, temperature, particle size and extraction time on the oil yield. Maximum extraction yield predicted from response surface method was 71.53% under the process conditions with pressure of 220 bar, temperature of 35 °C, particle diameter of 0.61 mm and extraction time of 130 min. Furthermore, broken and intact cells model was utilised to consider mass transfer kinetics of extracted natural materials. The results revealed that the model had a good agreement with the experimental data. The oil samples obtained via supercritical and solvent extraction methods were analysed by gas chromatography. The most abundant acid was linolenic acid. The results analysis showed that there was no significant difference between the fatty acid contents of the oils obtained by the supercritical and solvent extraction techniques.     

Novel composite membranes embedded with molecularly imprinted porous polymeric nanospheres for targeted phenol

In the present research, novel hybrid molecularly imprinted polymer (HMIP) membranes were synthesized for selective adsorption and separation of phenol toxic molecules from aqueous solutions. Molecularly imprinted polymer (MIP) nanospheres for targeted phenol were successfully prepared using precipitation polymerization of methacrylic acid, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate, followed by integrating into polysulfone matrix to create the HMIP membranes via a phase inversion method. The fabricated materials were characterized from the viewpoints of spectroscopic analysis, structural and surface morphological properties, porosimetry, and batch rebinding assays. The imprinted polymeric nanospheres with mean diameter value ranging from 210 to 250 nm and average pore diameter of 8 nm were obtained according to the morphological and Brunauer–Emmett–Teller analysis, respectively. Scanning electron microscopy pictures demonstrated that the MIP spheres were uniformly distributed on the surface and in the bulk polymer phase of the hybrid membrane. The surface roughness, porosity, and permeate flux of membrane were significantly augmented by addition of the imprinted polymer particles in the dope solution. HMIP‐2 membrane containing 10 wt% of MIP showed the highest binding capacity and an excellent molecular recognition for phenol with respect to the correlative blank membrane. The selective recognition of phenol on the HMIP‐2 membrane was 3.5 times larger than the analogous compound (i.e. catechol). Moreover, the maximum separation factor of phenol was obtained as 2.19 relative to catechol through selective permeation studies, which was also observed for HMIP‐2 membrane. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation,characterization and analysis of novel polyimides with anthracene,carbazole and fluorene pendent architecture

Two series of new organosoluble and thermally stable polyimides containing anthracene, and fluorene pendants were prepared by a two-step solution polycondensation reaction of new synthesized diamines with commercially available dianhydrides. All intermediates and polymers were fully characterized by FTIR, NMR, and elemental analysis and their properties including solubility and thermal stability were studied. All the resulting polymers were amorphous with inherent viscosities ranged from 0.61 to 0.84 dL/g and were readily soluble in many organic solvents.