Chiral banana liquid crystals derived from sugars

This paper describes the synthesis and physical properties of a chiral bent-core liquid crystal containing the chiral non-aromatic central ring system 1,5-anhydro-2-desoxy-D-arabino-hexitol. The preparation involved a stepwise construction of the mesogenic side chains via a selective diesterification of glucal at positions three and six with 4-O-acetylbenzoyl chloride followed by selective deacetylation. Repeated esterification of the aromatic hydroxy group with a substituted benzoic acid and hydrogenation of the double bond resulted in the desired product. To our knowledge, this is the first banana shaped liquid crystal synthesized containing a sugar derivative as a chiral core. Investigation of the mesogenic properties and electro-optic experiments showed traditional calamitic phases along with banana phases.     

Uranyl carboxyphosphonates that incorporate Cd(II)

The hydrothermal treatment of UO₃, Cd(CH₃CO₂)₂·2H₂O, and triethyl phosphonoacetate results in the formation of Cd₂[(UO₂)₆(PO₃CH₂CO₂)₃O₃(OH)(H₂O)₂]·16H₂O (CdUPAA-1), [Cd₃(UO₂)₆(PO₃CH₂CO₂)₆(H₂O)₁₃]·6H₂O (CdUPAA-2), and Cd(H₂O)₂[(UO₂)(PO₃CH₂CO₂)(H₂O)]₂ (CdUPAA-3). CdUPAA-1 adopts a cubic three-dimensional structure constructed from planar uranyl oxide clusters containing both UO₇ pentagonal bipyramids and UO₈ hexagonal bipyramids that are linked by Cd(II) cations and phosphonoacetate to yield large cavities approximately 16 Å across that are filled with disordered water molecules. CdUPAA-2 forms a rhombohedral three-dimensional channel structure that is assembled from UO₇ pentagonal bipyramids that are bridged by phosphonoacetate. CdUPAA-3 is layered with the hydrated Cd(II) cations incorporated directly into the layers linking one-dimensional uranyl phosphonate substructures together. In this structure, there are complex networks of hydrogen bonds that exist within the sheets, and also stitch the sheets together.     

Fractional magnetization plateaus and magnetic order in the Shastry-Sutherland magnet TmB4

We investigate the phase diagram of TmB4, an Ising magnet on a frustrated Shastry-Sutherland lattice, by neutron diffraction and magnetization experiments. At low temperature we find Néel order at low field, ferrimagnetic order at high field, and an intermediate phase with magnetization plateaus at fractional values M/M_(sat)=1/7,1/8,1/9,... and spatial stripe structures. Using an effective S=1/2 model and its equivalent two-dimensional fermion gas we suggest that the magnetic properties of TmB4 are related to the fractional quantum Hall effect of a 2D electron gas.     

ChemInform Abstract: Experimental Evidence for the Existence of Neutral P6: A New Allotrope of Phosphorus.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Coatings with self-cleaning properties

The issue of self-cleaning significantly gained popularity due to the work of Barthlott and coworkers on the so called “Lotos-Effect^®”. They found out, that the cleanliness of the Lotos leaves originates from a combined effect of surface topography and hydrophobicity. The symbol of the beautiful Lotos flower as well as the fascination of surfaces being cleaned without any manual activity, simply by a rain shower, has since then stimulated the fantasy of many researchers. Our vision is to copy this mechanism from mother nature and to implement it into coating systems in such a way, that conventional application techniques, e.g. spray-coating, can be applied without the necessity of further process steps like e.g. soft lithography. Three different approaches will be presented in this paper. Roughness and contact angle measurements have been used to quantify the self-cleaning properties.     

Einsatz der Elektronenstrahl-Mikrosonde bei der Lösung metallurgischer Werkstoffprobleme

The electron-probe microonalysis provides a variety of informations on the condition of mettalic samples within the micro range, which in connection with an appropriate measuring technique enables numerous statements to be made on important metallographic problems. As examples from the operating practice of a high-quality steel plant the identification of structural constituents, determination of microsegregation, investigation of grain boundaries and material defects in steels are explained.