Origin of the Director Tilt in the Lyotropic Smectic C* Analog Phase: Hydration Interactions and Solvent Variations

The origin and long‐range correlation of the director tilt in the recently discovered phase, which is the lyotropic analog of the thermotropic smectic C* (SmC*) liquid crystalline phase, are investigated. Polarized micro‐Raman spectroscopy reveals that the director tilt in the phase originates from a tilting of the aromatic 2‐phenylpyrimidine cores of the surfactant molecules. Optical measurements of the tilt angle show that its magnitude decreases with increasing solvent concentration, suggesting that the long‐range inter‐lamellar correlation of the tilt directions is reduced at increasing thickness of the solvent layers. The phase diagrams with four different solvents (water, formamide, N‐methylformamide, N,N‐dimethylformamide) are investigated, showing that the phase is only formed with those solvents that exhibit a dense network of hydrogen bonds. This observation suggests that these hydrogen bond networks play an essential role in the long‐range correlation of the director tilt between adjacent surfactant layers. To verify this assumption, mixtures with deuterated solvents are investigated, showing that the tilt angle in the phase is indeed reduced by this modification of the solvent′s hydrogen bond network.     

A combined laser-induced breakdown and Raman spectroscopy Echelle system for elemental and molecular microanalysis

Raman and laser-induced breakdown spectroscopy is integrated into a single system for molecular and elemental microanalyses. Both analyses are performed on the same ~ 0.002 mm² sample spot allowing the assessment of sample heterogeneity on a micrometric scale through mapping and scanning. The core of the spectrometer system is a novel high resolution dual arm Echelle spectrograph utilized for both techniques. In contrast to scanning Raman spectroscopy systems, the Echelle–Raman spectrograph provides a high resolution spectrum in a broad spectral range of 200–6000 cm^? 1 without moving the dispersive element. The system displays comparable or better sensitivity and spectral resolution in comparison to a state-of-the-art scanning Raman microscope and allows short analysis times for both Raman and laser induced breakdown spectroscopy. The laser-induced breakdown spectroscopy performance of the system is characterized by ppm detection limits, high spectral resolving power (15,000), and broad spectral range (290–945 nm). The capability of the system is demonstrated with the mapping of heterogeneous mineral samples and layer by layer analysis of pigments revealing the advantages of combining the techniques in a single unified set-up.     

Dangling bonds in amorphous silicon investigated by multifrequency EPR

Paramagnetic coordination defects in undoped hydrogenated amorphous silicon (a-Si:H) are studied using multifrequency pulsed electron-paramagnetic resonance (EPR) spectroscopy at S-, X-, Q- and W-band microwave frequencies (3.6, 9.7, 34, and 94 GHz, respectively). The improved spectral information extractable from a multifrequency fitting procedure allows us to conclude that the g tensor exhibits a rhombic splitting instead of axial symmetry. Our methods allow for precise and accurate determination of the g tensor principal values g_x = 2.0079(2), g_y = 2.0061(2) and g_z = 2.0034(2) and their distribution parameters (g strain).     

The formation of 1.13 nm tobermorite under hydrothermal conditions: 1. The influence of quartz grain size within the system CaO–SiO2–D2O

The influence of grain size of quartz on the formation of 1.13 nm tobermorite in aerated autoclaved concrete was investigated by applying in-situ neutron diffraction. Experiments were performed at 210 °C/P_sat employing quartz of 8 μm and 16 μm, respectively. The results reveal changes in the reaction mechanism from solution control to diffusion control. The grain size of the quartz fraction clearly influences the occurrence of those changes. Based on those results an interpretation of former not clearly interpretable quenching experiments was performed. An interpretation using different reaction mechanisms for those experiments leads to a coherent picture of the reaction.     

Solvent-free self-assembly of C60 and cucurbit[7]uril using high-speed vibration milling

The synthesis of a cucurbit[7]uril-[60]fullerene supramolecular complex using a simple, green, and efficient pathway is reported for the first time. In the complex, which was found to be of the 1:2 type, the compounds interact weekly with each other. Since the complexation can be achieved by a solid-solid reaction without solvent both the waste and contact with harmful solvents can be reduced to a minimum. A significant increase of reaction rate and yield compared to the heterogeneous complexation was observed.     

New aromatic musk odorants: Design and synthesis

By appropriate structural modification of known musk odorants, new strong musk odorants have been discovered. Incorporation of supplementary CH₃ or CH₂ groups into the basic musk skeleton of type G only slightly modifies the global shape of the molecule but leads to densely packed structures of enhanced lipophilicity. For the construction of these highly substituted 1,2,3,4-tetrahydronaphthalenes, new annulation sequences (intramolecular mono- and dialkylations; see Schemes 3,6, and 8) have been developed and, in certain cases, the design of the target molecules was dictated by both structure-activity-relationship and synthetic considerations (e.g. 46 and 47 , Scheme 6). This work also presents an original solution to an analytical problem: the distinction between a C₂- and a C_s-symmetrical aromatic hydrocarbon (viz. 71 and 72 ) by conversion into a [Cr(CO)₃arene]complex.