Amino-functionalization of large-pore mesoscopically ordered silica by a one-step hyperbranching polymerization of a surface-grown polyethyleneimine

A simple method for surface functionalization of large-pore mesoporous silica by hyperbranching polymerization resulting in a high loading of amine groups is presented.     

Experimental study on the reaction pathway of α‐haloacetophenones with nucleophiles: direct substitution or carbonyl addition?

The reaction of PhCOCH₂Cl with OH^– gave the expected α‐substituted alcohol (PhCOCH₂OH) in addition to three dimer products. To clarify whether the substitution product is formed by direct S_N2 or via carbonyl addition, the reaction of PhCOCH₂Cl and OMe^– was examined. The reaction gave two products, PhCOCH₂OH as the major product after acid hydrolysis and PhCOCH₂OMe as the minor product. An electron‐withdrawing substituent on the phenyl ring enhanced the overall reactivity and gave more alcohol than ether. It was concluded that the alcohol was formed via carbonyl addition‐epoxidation route, whereas the ether was formed by the direct substitution route. Copyright © 2012 John Wiley & Sons, Ltd.     

Behavior of Glassy Carbon Paste Electrode in Flowing Methanolic Solutions

Carbon paste electrodes are often used for electrochemical determinations, but their application in media with high content of organic solvents, particularly in HPLC, is limited by their low stability. The work presented here examines the effect of a moving methanol‐containing solution on a glassy carbon paste electrode by studying its electrochemical behavior in relation to the period of contact and methanol content in the solution. In combination with microscopic observation of the paste surface it can be concluded that the electrode is affected by the methanolic solution and the surface roughness increases, resulting in the stable state compatible with measurements in highly methanolic solutions.     

Morphological lattice complexes

Binary and pseudobinary compounds AB like NaCl and CaCO₃, with the center of charge at carbon position, are characterized by self‐coordination numbers of nearest, second and third neighbors T ₁ T ₂ T ₃ of A and B positions. The maximum Madelung factor of compounds with identical T _i values of A and B atoms is obtained for a maximum of B positions at the border of the A–A Dirichlet domain. The A and B positions form a packing with different T _i values, if all B positions are on the border of the Dirichlet domain. This packing like the primitive cubic packing of Na and Cl atoms with T _i values 6 12 8 or the rhombohedrally distorted packing 6 8 6 of CaCO₃ as morphological lattice complexes can be related to cubic NaCl crystals or the cleaved rhombohedron of calcite. A different habit of crystals is expected for sphere, rod or layered packings. Many well‐defined nanoparticles can be obtained from microemulsions at variation of temperature, water content or water partial pressure. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Extended conformations of isolated molecular bottle-brushes: Influence of side-chain topology

A Monte Carlo study is presented to discuss the influence of the side-chain topology on the enhancement of the persistence length of a molecular bottle-brush in a dilute athermal solution due to the excluded volume interactions between the side chains. The structures investigated consisted of freely jointed backbones of 100 hard spheres (beads) of diameter 1 to which 50 equally flexible side chains were grafted. The diameter of the side-chain beads was varied from 1 to 3 in the same units. For every given size of the side-chain bead, the length of the side chains was varied from 4 to 20 beads. The ratio between the persistence length and the bottle-brush diameter, which is the determining factor for lyotropic behavior of conventional semi-flexible chains, was found to be almost independent of the side-chain length. At the same time, it was found to increase considerably with increasing size of the side-chain beads, suggesting that by a proper choice of the chemistry lyotropic behavior of molecular bottle-brushes due to excluded-volume interactions between the side chains might be achieved. Moreover, relatively short side chains can be used since the side chain length has only a minor influence on the ratio between the persistence length and the diameter. These findings are in a good agreement with recent experimental observations.