Excluded volume effects and fractional viscoelasticity in polymers

Meccanica - The excluded volume effect is added to a fractional viscoelastic model for modeling fractal polymers. This reveals a physical connection between the fractional time derivative, fractal...     

Simultaneous determination of vitamin B12 and its derivatives using some of multivariate calibration 1 (MVC1) techniques

Resolution of binary mixtures of vitamin B12, methylcobalamin and B12 coenzyme with minimum sample pre-treatment and without analyte separation has been successfully achieved by methods of partial least squares algorithm with one dependent variable (PLS1), orthogonal signal correction/partial least squares (OSC/PLS), principal component regression (PCR) and hybrid linear analysis (HLA). Data of analysis were obtained from UV-vis spectra. The UV-vis spectra of the vitamin B12, methylcobalamin and B12 coenzyme were recorded in the same spectral conditions. The method of central composite design was used in the ranges of 10-80mgL(-1) for vitamin B12 and methylcobalamin and 20-130mgL(-1) for B12 coenzyme. The models refinement procedure and validation were performed by cross-validation. The minimum root mean square error of prediction (RMSEP) was 2.26mgL(-1) for vitamin B12 with PLS1, 1.33mgL(-1) for methylcobalamin with OSC/PLS and 3.24mgL(-1) for B12 coenzyme with HLA techniques. Figures of merit such as selectivity, sensitivity, analytical sensitivity and LOD were determined for three compounds. The procedure was successfully applied to simultaneous determination of three compounds in synthetic mixtures and in a pharmaceutical formulation.     

Investigating the effects of nanoparticles mean diameter on laminar mixed convection of a nanofluid through an inclined tube with circumferentially nonuniform heat flux

In this study, laminar mixed convection of a water-based nanofluid containing Al₂O₃ nanoparticles in an inclined copper tube, which is heated at the top half surface, is investigated numerically. A heat conduction mechanism through the tube wall was implemented. Three-dimensional equations using a two-phase mixture model were solved to investigate the hydrodynamic and thermal behaviors of the nanofluid over a wide range of nanoparticle volume fractions. To verify the model, the results were compared with previous works and a good agreement between the results was observed. The effect of nanoparticles diameter on the hydrodynamic and thermal parameters over a wide range of Grashof numbers is presented and discussed for a particle volume fraction and Reynolds number. It is shown that the diameter of nanoparticles affects the particle distribution in the cross section perpendicular to the tube axis, heat transfer coefficient, and shear stress.     

The effect of initiators and oxidants on the morphology of poly [(±)‐2‐(sec‐butyl) aniline] a chiral bulky substituted polyaniline derivative

The nano and micro sphere synthesis of chiral bulky substituted polyaniline from monomer (±)‐2‐sec‐butylaniline in bulk and template‐free method (rapid mixing) was done successfully using ammonium peroxydisulfate (APS) and FeCl₃·6H₂O as oxidants. The effect of initiators such as p‐phenylendiamine and 1,4‐benzenediamine, temperature and concentration of monomer on morphology is demonstrated by scanning electron microscopy (SEM) images. The nano and micro sphere morphology was obtained using initiators. Smallest particles were achieved when 1,4‐benzenediamine was used as initiator in the presence of FeCl₃·6H₂O as oxidant. By increasing the concentration of monomer more uniform spheres were obtained. Characterization was made via FT‐IR, UV–Vis, ¹H and ¹³C‐NMR spectroscopy. Elemental analysis and electrical conductivity of products are also presented. All analysis data are in good agreement with nigraniline oxidation state of polyaniline. Copyright © 2015 John Wiley & Sons, Ltd.     

A stoichiometric imprinted chelating resin for selective recognition of copper(II) ions in aqueous media

This work reports the preparation of a new copper(II) ion-imprinted polymer (IIP) material, using 5,6;14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadecane-5,14-diene (DBDA15C4) and 2-vinylpyridine (VP) as a non-vinylated chelating agent and a functional vinyl monomer, respectively. The Cu²⁺ ion can form stable complexes with DBDA15C4 and VP. The stoichiometries of Cu²⁺-DBDA15C4 and ternary Cu²⁺-DBDA15C4-VP complexes were elucidated using conductometric and spectrophotometric methods, and found to be Cu²⁺(DBDA15C4), Cu²⁺(DBDA15C4)₂ and Cu²⁺(DBDA15C4)(VP)₂. The results obtained from solution studies were also supported by ab initio theoretical calculations. The resulting ternary complex Cu²⁺(DBDA15C4)(VP)₂ was copolymerized with ethyleneglycoldimethacrylate, as a cross-linking monomer, via bulk polymerization method. The imprinted copper ion was removed from the polymeric matrix by 0.1 M HNO₃. The Cu²⁺-imprinted polymer particles were characterized by IR spectroscopy and elemental analysis. Optimum pH range for rebinding of Cu²⁺ on the IIP and equilibrium binding time were 7.0-7.5 and 45 min, respectively. Sorbent capacity and enrichment factor for Cu²⁺ were obtained as 75.3 ± 1.9 μmol g⁻¹ and 100, respectively. In selectivity study, it was found that imprinting results in increased affinity of the material toward Cu²⁺ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for five times without a significant decrease in polymer binding affinities.     

Fe3O4–SiO2–Bi2O3-catalyzed One-Pot Synthesis of Tetrahydrobenzo[b]pyran Derivatives Under Solvent-Free Conditions

Russian Journal of Organic Chemistry - A Fe3O4–SiO2–Bi2O3 magnetic nanocatalyst was used to synthesize tetrahydrobenzo[b]pyran derivatives from malononitrile, cyclohexane-1,3-dione, and...     

Guiding in the visible with "colorful" solid-core Bragg fibers

We report on the fabrication and characterization of solid-core all-polymer Bragg fibers consisting of a large-diameter polymethyl methylacrylate (PMMA) core surrounded by 50 alternating PMMA/Polystyrene (PS) polymer layers. By modifying the reflector layer thickness we illustrate that bandgap position can be adjusted at will in the visible. Moreover, such fibers are intensely colored in both the transmission and the outside reflection modes. Potential applications of such fibers are discussed.     

Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds

Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1).     

Optimization of simultaneous derivatization and extraction of aliphatic amines in water samples with dispersive liquid-liquid microextraction followed by HPLC

Dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) with simultaneous derivatization followed by high-performance liquid chromatography-diode array detection (HPLC-DAD) was applied for preconcentration and determination of primary and secondary aliphatic amines in environmental water samples. A ternary mixture consisting of a disperser, an extractant and a derivatization reagent was used for the simultaneous derivatization and extraction of aliphatic amines in different water samples. The effects of various experimental parameters on derivatization and extraction efficiency were studied simultaneously using experimental design. A Plackett-Burman design was performed for screening of variables in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by using a Box-Behnken design (BBD) and the response surface equations were derived. Under optimal conditions, the preconcentration factors were between 210 and 290. The limit of detections (LODs) ranged from 0.005 to 0.02 μg/L and dynamic linear ranges (DLRs) of 0.05-500 and 0.1-500 μg/L were obtained for most of analytes. The performance of the method was evaluated for extraction and determination of primary and secondary aliphatic amines in environmental water samples in micrograms per liter and satisfactory results were obtained (RSDs <12.5%).     

Chemoselective synthesis of 4‐oxo‐2‐aryl‐4,10‐dihydropyrimido [1,2‐a][1,3]benzimidazol‐3‐yl cyanides via [3+3] atom combination of 2‐aminobenzimidazole with ethyl‐α‐cyanocinnamoates

Chemoselective synthesis of 4‐oxo‐2‐aryl‐4,10‐dihydropyrimido[1,2‐a][1,3]benzimidazol‐3‐yl cyanides from three‐component reactions of 2‐aminobenzimidazole, aldehydes, and ethyl cyanoacetate via [3+3] atom combination is reported. The effect of different base catalysts such as sodium acetate, triethylamine, and magnesium oxide MgO on the product yield has also been investigated under conventional heating. J. Heterocyclic Chem., (2011).