Characterization of Nanocomposite Coatings in the System Ti–B–N by Analytical Electron Microscopy and X-Ray Photoelectron Spectroscopy

 Superhard nanocomposite coatings of different composition in the quasi-binary system TiN–TiB₂ were deposited onto stainless steel sheets by means of unbalanced DC magnetron co-sputtering using segmented TiN/TiB₂ targets. The chemistry and microstructure of a TiB_0.6N_0.7 coating was investigated using X-ray and electron diffraction, photoelectron spectroscopy, energy-filtering transmission electron microscopy, and electron energy-loss spectrometry. High resolution elemental mapping of the elements Ti, B, N, and O with energy-filtering TEM reveals a homogeneous distribution on the nanometer scale. X-Ray and electron diffraction exhibit only TiN crystallites of nanometer size, but no information on the boron-rich phase. The near-edge fine structures of the BK and NK ionization edges in the EELS spectra of the Ti–B–N coatings were used to derive information on the phases by comparing the edges with those of reference compounds. It was found that the TiN nanocrystals occur together with TiO _x particles; the grains are embedded in a strongly disordered or quasi-amorphous matrix consisting mainly of TiB₂ particles and, near the steel substrate, also boron oxide (B₂O₃).     

ansa-Metallocene derivatives: VII. Synthesis and crystal structure of a chiral ansa-zirconocene derivative with ethylene-bridged tetrahydroindenyl ligands

The chiral ansa-zirconocene derivative ethylenebis(4,5,6,7-tetrahydro-1-indenyl)-zirconium(IV) dichloride has been prepared by reaction of dilithiobis(indenyl)ethane with ZrCl₄ and subsequent hydrogenation. The product has been shown to be the 1-R,S rather than meso-metal-ring linkage stereoisomer by an X-ray determination of the molecular structure.     

D-lattices

Difference lattices (D-lattices), which generalize Boolean algebras, orthomodular lattices as well as MV algebras, are studied.     

Multifunctional amphiphilic siloxane architectures using sequential,metal‐free click ligations

Polysiloxanes or silicones are a class of macromolecules widely used in commerce because of their exceptional properties. Their derivatization leads to functional silicones with added value and properties, such as surfactants and liquid crystals, among many others. However, most silicone surfactants are monofunctional, owing to the synthetic challenges associated with the introduction of multiple functional groups onto the hydrolytically sensitive siloxane backbone. Thus, general routes to surface active silicones with multiple and different functional groups are not available. Herein, a synthetic strategy is reported that permits sequential derivatization of silicones with hydrophiles including oligo(ethylene oxides), carboxylic acids, and bromoalkylesters using a simple metal‐free Click reaction: the process benefits from mild conditions, extremely high yields and does not generate any by‐products, allowing the facile preparation of di‐ and trifunctional silicones that could not be readily obtained using traditional methods. The products exhibit amphiphilic characteristics as demonstrated through interfacial tension measurements that yielded the critical aggregation concentration of selected compounds. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Chemoenzymatic Synthesis of All Four Diastereomers of 2,6‐Disubstituted Piperidines through Stereoselective Monoamination of 1,5‐Diketones

The regioselectivity of various enantiocomplementary ω‐transaminases was evaluated for the stereoselective monoamination of designated 1,5‐diketones; excellent conversions, enantio‐ and regioselectivities were observed. The resulting amino‐ketones underwent spontaneous intramolecular ring closure to afford Δ1‐piperideines, which served as precursors for the cis‐ and anti‐piperidine scaffold as demonstrated for the synthesis of the alkaloids dihydropinidine and epi‐dihydropinidine. Key to the success of accessing the trans‐piperidines was a Lewis acid mediated conformational change of the Δ1‐piperideines in the reduction step. Thus, all four diastereomers of 2,6‐disubstituted piperidines could successfully be prepared.     

Adsorption of water on Grace Silica Gel 127B at low and high pressure

An application of the original Dubinin-Radushkevitch equation modified with based on Polanyi theory, which taking into consideration the self-associating molecules in heterogeneous microporous structures at low and high uptake was presented. The Polanyi-Dubinin models were applied to predicting the behavior of water adsorption on Grace Silica Gel 127B at pressures not yet reported in the literature. The heat of adsorption, differential entropy, henry ratio was obtained from adsorption isotherm. The resulting extensions are experimentally and analytically presented. The coefficient of multiple correlation (R ²) between the thermogravimetric measurements and the MDR equation was 0.9924, which is 8.13% better than the best Dubinin-Astakhov fit.     

Hydrolytically stable linkers for silicone carbohydrates derived from hydrodiisopropylsilanes

Two strategies were developed for the attachment of sugars to siloxanes using bifunctional silicon linkers: the substrate could be functionalized with a silyl hydride before coupling to a vinyl-terminated siloxane through platinum catalyzed hydrosilylation; alternatively, unprotected glucose could be directly silylated by a silicone terminated with a chlorosilyl group. Optimal steric bulk was found with difunctional diisopropylsilanes, which exhibit excellent reactivity for preparation of sugarsilane derivatives, and also permit efficient grafting to silicones via hydrosilylation. The resulting product alkoxysilane-silicone exhibits greater stability to hydrolysis than the silicone itself.