Effect of montmorillonite on the structure and properties of powder epoxy compounds for polymeric coatings

Procedures for preparing nanomodified powder epoxy compounds with various concentrations of montmorillonite were examined. The dispersion of particles in the epoxy oligomers was studied by X-ray diffraction analysis and electron microscopy. The influence of the content of the modifiers on the physicomechanical properties of cured block specimens was analyzed.     

Multi-component reactions between 2-aminopyrimidine, aldehydes and isonitriles: the use of a nonpolar solvent suppresses formation of multiple products

A reliable and convenient protocol for MCRs between 2-aminopyrimidine, aldehydes and isonitriles is described. Toluene was chosen as the reaction solvent based on mechanistic reasoning. The product mixtures were found to contain a single imidazo[1,2-a]pyrimidine product in each case, which were isolated and purified by precipitation and crystallization. Chromatographic recovery from filtrates raised the total yields to 49-66%. The procedure provides a practical alternative to hitherto reported methods in which formation of multiple products was observed.     

Linear-dendritic nonionic poly(propylene oxide)-polyglycerol surfactants

A new type of linear-hyperbranched surfactant has been prepared by anionic ring-opening multibranching polymerization of glycidol onto an end-functional poly(propylene oxide) (PPO) macroinitiator. A hyperbranched, highly hydrophilic polyglycerol block is obtained as the polar segment of the structure. Molecular weights of the nonionic amphiphiles obtained were in the range of 390 to 8,600 g/mol. For comparison, initiators bearing a C16 alkyl chain have also been employed. Furthermore, hyperbranched polyglycerol homopolymers were investigated with respect to amphiphilic properties. All linear-dendritic amphiphiles have been characterized by SEC, DSC, ¹³C and ¹H NMR spectroscopy. A fluorescence-probe technique based on diphenyl hexatriene (DPH) as probe molecule was employed to determine the CMC (critical micelle concentration) of the samples in water. CMCs varied from 7.5×10⁻⁶ to 1.7×10⁻³ M and were found to depend on the copolymer architecture and the hydrophilic/hydrophobic balance. Measurements at pH 6.75 and 3.00 revealed an increase of the CMC by a factor of 10 for the amine containing copolymers upon lowering of the pH.     

Characterization of Powder Beds by Thermal Conductivity: Effect of Gas Pressure on the Thermal Resistance of Particle Contact Points

The thermal conductivity of ceramic powder packed beds was measured at temperatures below 100 °C for various powder sizes and compositions and under different gas atmospheres. Measurements at low pressures (down to 10 Pa) combined with a theoretical model allowed the elucidation of geometrical and thermal resistance parameters for the contact points between granules. The gap thickness and contact point size were found to be well correlated with the mean particle size. The thermal conductivities of all powders at low pressure were found to differ at most by a factor of two, whereas the solid‐phase conductivities of the powder materials differed by more than one order of magnitude. A theoretical model accounting for the size‐dependence of contact point conductivity is incorporated to rationalize this trend.     

Darboux transformation and elementary exact solutions of the Schrödinger equation

Darboux transformation is applied to three classical potentials, namely the harmonic oscillator, effective Coulomb and Morse potentials to generate exactly solvable potentials of elementary form. For every potential, the isospectral families of potentials are constructed. For almost all potentials, a set of normalized discrete spectrum wave functions is given.     

Spin-wave eigenmodes of a saturated magnetic square at different precession angles

Using low-loss dielectric magnetic films in combination with space-resolved Brillouin light scattering spectroscopy we have studied nonlinear modification of eigenmode spatial distributions in saturated magnetic squares. We have found that, as the angle of magnetization precession increases, the eigenmode spatial distributions experience significant qualitative changes due to a nonlinear coupling between forming them standing spin waves. We show that the found nonlinear eigenmodes cannot be described by means of the linear theoretical approach even qualitatively.     

Extending N-heterocyclic carbene ligands into the third dimension: a new type of hybrid phosphazane/NHC system

A simple, “click” synthetic approach to a new type of hybrid phosph(III)azane/NHC system is described. The presence of the phosphazane P₂N₂ ring unit, with P atoms flanking the NCN fragment and with this ring perpendicular to the binding site of the NHC, provides unique opportunities for modifying the electronic and steric character of these carbenes.     

Microwave-assisted aza-Prins reaction. Part 1: facile preparation of natural-like 3-azabicyclo[3.3.1]non-6-enes

A facile and operationally simple route to diastereomerically pure, natural-like 3-azabicyclo[3.3.1]non-6-enes via microwave-assisted, BF₃·OEt₂-promoted aza-Prins reaction has been developed. Complexity-generating transformations based on these products involving reactive functionalities introduced during the aza-Prins step have been developed.     

Size separation of proteins by capillary zone electrophoresis with cationic hitchhiking

The paper describes a method of size separation of proteins by capillary sieving electrophoresis with cationic surfactant. Proteins are separated within 12 min with repeatability of migration times better than 0.2%. Some proteins achieve the separation efficiency of 200,000 theoretical plates. The method can be used for determination of protein relative molecular masses. The accuracy of the determined relative molecular masses and the limitation of the method were investigated by the analysis of more than 60 proteins. The method also allows separation of protein oligomers. Proteins can be quantitated after the electrokinetic injection in the concentration range 0.07-0.43?g/L. The average detection limit is about 2?mg/L.     

A simple synthesis of the pentacyclic lamellarin skeleton from 3-nitro-2-(trifluoromethyl)-2H-chromenes and 1-methyl(benzyl)-3,4-dihydroisoquinolines

The basic structural framework of lamellarin alkaloids, 8,9-dihydro-6H-chromeno[4′,3′:4,5]pyrrolo[2,1-a]isoquinoline derivatives, has been obtained in good yields via Grob synthesis between 3-nitro-2-(trifluoromethyl)-2H-chromenes and 1-methyl-3,4-dihydroisoquinolines in refluxing isobutanol. In the case of 1-benzyl-3,4-dihydroisoquinolines, a dynamic NMR effect was observed in the ¹H and ¹⁹F NMR spectra of the products as a result of restricted rotation about the single bond linking the benzene ring and the heterocyclic system. When the reaction was carried out with 3-nitro-2-(trichloromethyl)-2H-chromenes in toluene at room temperature, only Michael adducts, as a mixture of two diastereomers, were isolated.