Use of surfactants in cellulose nanowhisker/epoxy nanocomposites: effect on filler dispersion and system properties

Cellulose nanowhiskers (CNWs) prepared via TEMPO mediated oxidation are used as biodegradable filler in an epoxy matrix. Since CNWs are hydrophilic and epoxy is hydrophobic, amphiphilic block copolymer surfactants are employed to improve the interactions between the filler and the matrix. The surfactants used are Pluronics, a family of triblock copolymers containing two poly(ethylene oxide) blocks and one poly(propylene oxide) block. In this study, Pluronic L61 and L121 with molecular weight of 2000 and 4400 g/mol and hydrophilic to lipophilic balance of 3 and 1 respectively, are used and their effect on the dispersion of CNWs in epoxy is discussed. The hydrophilic tails of Pluronics interact with the hydroxyl and carboxylic groups on the CNW surface and then these surfactant-treated CNWs are directly incorporated into epoxy by high speed mixing. The dispersion state of the surfactant-treated CNWs in epoxy is assessed by rheological measurements and the mechanical properties of the resulting composites are characterized by tensile test and dynamic mechanical thermal analysis. The Pluronic L61 treated CNW/epoxy composites show the highest storage modulus at high temperatures (about 77 % increases) indicative of improved interfacial interactions between the CNWs and the epoxy matrix. Also, an increase of around 10 °C in the glass–rubbery transition temperature of the L61 treated CNW/epoxy composite leads to potential application at higher service temperatures.     

Regioselective N‐Arylation of Some Pyrimidine and Purine Nucleobases

N‐Arylation of some pyrimidine and purine nucleobases in the presence of SiO₂ and Cs₂CO₃ under solvent‐free as well as in solution conditions is described. In these conditions, N1‐aryl pyrimidines and N9‐aryl purines have been obtained regioselectively in moderate to high yields with relatively short reaction times.     

Dynamic heat and moisture transfer in bulky PAN nanofiber mats

In this study a non-conventional electrospinning technique was designed for the production of high bulky polyacrylonitrile (PAN) nanofiber mats. Optimum nanofiber mats are achieved with 15 wt.% solution of PAN in dimethylformamide. Such mats result in a bulk porosity which is as high as 99.9 and a density as low as 0.84 × 10⁻³ g/cm³. The effect of the porosity of nanofiber mats on the air permeability and coupled heat and moisture transfer of fibers was investigated. Based on the results, high bulky nanofiber mats possess high heat and moisture transfer. Experimental data reveal that upon a slight decrease in the bulk porosity, air permeability and heat transfer decrease noticeably, while moisture transfer variation is low.     

Boron nitride nanocluster as a carrier for lomustine anticancer drug delivery: DFT and thermodynamics studies

Monatshefte für Chemie - Chemical Monthly - Previous reports were shown that boron nitride nanostructures can be biocompatible and nontoxic. Therefore, interaction of lomustine as an...     

Synthesis and Computational Study of Phosphorus Ionic Liquids

The synthesis of six tetraalkylammonium bromopentachlorophosphoride ionic liquids (ILs) is reported here. Their structures were determined by IR, ¹H NMR, and ¹³C NMR spectroscopy. Moreover, thermogravimetric (TG) and differential thermal analysis (DTA) were used to investigate the thermal behavior of these compounds. The results show that these ILs have excellent thermal stability below 145°C, and by decreasing the size of the alkyl groups, the thermal stabilities will increase. Along with the experimental study, these compounds have been studied computationally at the B3LYP/LANL2DZ level of theory using the PC GAMESS/Firefly program package. From these calculations, optimized geometries, molecular parameters, and vibrational spectra of ILs have been calculated. In addition, calculated frequencies are compared with the experimental frequencies after correction by the appropriate scaling factor. This comparison shows that our theoretical data are in good agreement with the experimental results.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Second derivative backward differentiation formulae for ODEs based on barycentric rational interpolants

Numerical Algorithms - For their several attractive features from the viewpoint of the numerical computations, linear barycentric rational interpolants have been recently used to construct various...     

Copper nanoparticles supported on 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41: An efficient and recyclable catalyst for one‐pot three‐component C–S coupling reaction of aryl halides with benzyl bromide and thiourea

An environmentally friendly copper‐based catalyst supported on 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 was prepared and characterized by Fourier transform‐infrared, transmission electron microscopy, field emission‐scanning electron microscopy, X‐ray diffraction and inductively coupled plasma techniques. The catalyst was applied for the one‐pot three‐component C–S coupling reactions of aryl halides with benzyl bromide and thiourea under aerobic conditions to afford the corresponding coupled products in good yields in water. The catalyst could be recovered and recycled five times. These results prove 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 supported Cu (II) complex was not leached during the reaction. Also it shows the correct heterogeneous nature of the catalyst.     

Enhanced synchronous spectrofluorimetric determination of aflatoxin B1 in pistachio samples using multivariate analysis

The determination of aflatoxin B₁ (AFB1) in pistachio has been accomplished by normal and synchronous fluorimetry in combination with some multivariate calibration methods and derivative techniques. Extending the two-dimensional synchronous fluorescence scan to a three-dimensional total synchronous fluorescence scan was used to obtain the optimized Δλ for AFB1 in pistachio sample. The methods are based on the enhanced fluorescence of AFB1 by β-cyclodextrine in 10% (v/v) methanol-water solution. Twenty-six pistachio samples containing AFB1 in the range 0-15 ppb were used as calibration set. Eighteen combinational methods were tested to make best model for prediction of AFB1 and finally best results obtained using a method based on synchronous fluorimetry in combination with multiple linear regressions (MLR). For concentrations ranging from 0 to 15 ppb of AFB1 in 22 pistachio samples as prediction set, the values of root mean square difference (RMSD) and relative error of prediction (REP) using MLR were 0.328 and 4.453%, respectively were observed. Two naturally contaminated pistachio samples were analyzed by synchronous fluorimetry using MLR and compared with HPLC results.     

The phenomenon of simplified scattering from rough surfaces to reflection in fractional space

In this paper, the scattering of incident plane waves from rough surfaces has been modeled in a fractional space. It is shown how wave scattering from a rough surface could correspond to a simple reflection problem in a fractional space. In an integer dimensional space, fluctuations of the surface result in wave scattering, while in the fractional space, these fluctuations are compensated by the geometry of space. In the fractional space, reflection is equivalent to scattering from the integer dimensional space. Comparing scattered wave functions from different self-affine rough surfaces in the framework of the Kirchhoff theory with the results from the fractional space, we see good agreement between them.