2015, Schirmer, Marie-Luis, Spannenberg, Anke, Werner, Thomas

The title compound, C17H18O5, was synthesized by a base-free catalytic Wittig reaction. The mol­ecule consists of a diethyl itaconate unit, which is connected via the C=C double bond to a benzo­furan moiety. The benzo­furan ring system (r.m.s. deviation = 0.007 Å) forms dihedral angles of 79.58 (4) and 12.12 (10)° with the mean planes through the cis and trans eth­oxy­carbonyl groups, respectively. An intra­molecular C-H...O hydrogen bond involving the O atom of the benzo­furan moiety is observed. In the crystal, mol­ecules are linked into ribbons running parallel to the b axis by C-H...O hydrogen bonds.

2015, Sonneck, Marcel, Peppel, Tim, Spannenberg, Anke, Wohlrab, Sebastian

The crystal structure of (E)-dodec-2-enoic acid, C12H22O2, an [alpha],[beta]-unsaturated carb­oxy­lic acid with a melting point (295 K) near room temperature, is characterized by carb­oxy­lic acid inversion dimers linked by pairs of O-H...O hydrogen bonds. The carb­oxy­lic acid group and the following three carbon atoms of the chain of the (E)-dodec-2-enoic acid mol­ecule lie almost in one plane (r.m.s. deviation for the four C atoms and two O atoms = 0.012 Å), whereas the remaining carbon atoms of the hydro­carbon chain adopt a nearly fully staggered conformation [moduli of torsion angles vary from 174.01 (13) to 179.97 (13)°].

2015, Arndt, Perdita, Schubert,Kathleen, Burlakov, Vladimir V., Spannenberg, Anke, Rosenthal, Uwe

The crystal structure of the title compound, [Hf(C10H15)2(C4H9)2], reveals two independent mol­ecules in the asymmetric unit. The diffraction experiment was performed with a racemically twinned crystal showing a 0.529 (5):0.471 (5) component ratio. Each HfIV atom is coordinated by two penta­methyl­cyclo­penta­dienyl and two n-butyl ligands in a distorted tetra­hedral geometry, with the cyclo­penta­dienyl rings inclined to one another by 45.11 (15) and 45.37 (16)°. In contrast to the isostructural di(n-butyl)bis([eta]5-penta­methyl­cyclo­penta­dien­yl)zirconium(IV) complex with a noticeable difference in the Zr-butyl bonding, the Hf-Cbut­yl bond lengths differ from each other by no more than 0.039 (3) Å.

2014, Krause, Beate, Pötschke, Petra, Gohs, U.

Polymer modification with high energy electrons (EB) is well established in different applications for many years. It is used for crosslinking, curing, degrading, grafting of polymeric materials and polymerisation of monomers. In contrast to this traditional method, electron induced reactive processing (EIReP) combines the polymer modification with high energy electrons and the melt mixing process. This novel reactive method was used to prepare polymer blends and composites. In this study, both methods were used for the preparation of polyethylene (PE)/ multiwalled carbon nanotubes (MWCNT) composites in the presence of a coupling agent. The influence of MWCNT and type of electron treatment on the gel content, the thermal conductivity, rheological, and electrical properties was investigated whereby as-grown and oxidised MWCNT were used. In the presence of a coupling agent and at an absorbed dose of 40 kGy, the gel content increased from 57 % for the pure PE to 74 % or 88 % by the addition of as-grown (Baytubes® C150P) or oxidised MWCNT, respectively. In comparison to the composites containing the as-grown MWCNTs, the use of the oxidised MWCNTs led to higher melt viscosity and higher storage modulus due to higher yield of filler polymer couplings. The melt viscosity increased due to the addition of MWCNT and crosslinking of PE. The thermal conductivity increased to about 150 % and showed no dependence on the kind of MWCNT and the type of electron treatment. In contrast, the lowest value of electrical volume resistivity was found for the non-irradiated samples and after state of the art electron treatment without any influence of the type of MWCNT. In the case of EIReP, the volume resistivity increased by 2 (as-grown MWCNT) or 3 decades (oxidised MWCNT) depending on the process parameters. © 2014 American Institute of Physics.

2015, Becker, Lisanne, Spannenberg, Anke, Arndt, Perdita, Rosenthal, Uwe

The title compound, [Zr2(C10H15)4(C6H6N2)2]·C6H14, was obtained by the stoichiometric reaction of adipo­nitrile with [Zr(C10H15)2([eta]2-Me3SiC2SiMe3)]. Intra­molecular nitrile-nitrile couplings and deprotonation of the substrate produced the (1-imino-2-enimino)­cyclo­pentane ligand, which functions as a five-membered bridge between the two metal atoms. The ZrIV atom exhibits a distorted tetra­hedral coordination sphere defined by two penta­methyl­cyclo­penta­dienyl ligands, by the imino unit of one (1-imino-2-enimino)­cyclo­pentane and by the enimino unit of the second (1-imino-2-enimino)­cyclo­pentane. The cyclo­pentane ring of the ligand shows an envelope conformation. The asymmetric unit contains one half of the complex and one half of the hexane solvent mol­ecule, both being completed by the application of inversion symmetry. One of the penta­methyl­cyclo­penta­dienyl ligands is disordered over two sets of sites with a refined occupancy ratio of 0.8111 (3):0.189 (3). In the crystal, the complex mol­ecules are packed into rods extending along [100], with the solvent mol­ecules located in between. The rods are arranged in a distorted hexa­gonal packing.

2015, Sonneck, Marcel, Peppel, Tim, Spannenberg, Anke, Wohlrab, Sebastian

In the mol­ecule of the title low-melting [alpha],[beta]-unsaturated carb­oxy­lic acid, C11H20O2, the least-squares mean line through the octyl chain forms an angle of 60.10 (13)° with the normal to plane of the acrylic acid fragment (r.m.s. deviation = 0.008 Å). In the crystal, centrosymmetrically related mol­ecules are linked by pairs of O-H...O hydrogen bonds into dimers, forming layers parallel to the (041) plane.

2016, Scheffler, C., Wölfel, E., Förster, T., Poitzsch, C., Kotte, L., Mäder, G., Madsen, Bo, Biel, A., Kusano, Y., Lilholt, H., Mikkelsen, L.P., Mishnaevsky Jr., L., Sørensen, B.F.

A commercially available carbon fiber (CF) with an epoxy-based sizing (EP-sized CF) and an unsized CF have been plasma treated to study the effect on the fiber-matrix adhesion towards a polypropylene matrix. The EP-sized fiber was chosen because of its predictable low adhesion in a polypropylene (PP) matrix. The fibers have been modified using a microwave low-pressure O2/CO2/N2-gas plasma source (Cyrannus®) developed at IWS in a batch process. One aim of this study was the evaluation of parameters using high energies and short time periods in the plasma chamber to see the effect on mechanical performance of CF. These results will be the fundamental work for a planned continuous plasma modification line. The CF surface was characterized by determining the surface energies, single fiber tensile strength and XPS analysis. The adhesion behavior before and after plasma treatment was studied by single fiber pull-out test (SFPO) and scanning electron microscopy (SEM). It was shown that the CO2- and O2-plasma increases the number of functional groups on the fiber surface during short time plasma treatment of 30 s. Carboxylic groups on the unsized CF surface resulting from O2-plasma treatment lead to an enhanced fiber-matrix adhesion, whereas the fiber strength was merely reduced.

2017, Wang, Tao, Li, Peining, Chigrin, Dmitry N., Giles, Alexander J., Bezares, Francisco J., Glembocki, Orest J., Caldwell, Joshua D., Taubner, Thomas

A conventional thermal emitter exhibits a broad emission spectrum with a peak wavelength depending upon the operation temperature. Recently, narrowband thermal emission was realized with periodic gratings or single microstructures of polar crystals supporting distinct optical modes. Here, we exploit the coupling of adjacent phonon-polaritonic nanostructures, demonstrating experimentally that the nanometer-scale gaps can control the thermal emission frequency while retaining emission line widths as narrow as 10 cm-1. This was achieved by using deeply subdiffractional bowtie-shaped silicon carbide nanoantennas. Infrared far-field reflectance spectroscopy, near-field optical nanoimaging, and full-wave electromagnetic simulations were employed to prove that the thermal emission originates from strongly localized surface phonon-polariton resonances of nanoantenna structures. The observed narrow emission line widths and exceptionally small modal volumes provide new opportunities for the user-design of near- and far-field radiation patterns for advancements in infrared spectroscopy, sensing, signaling, communications, coherent thermal emission, and infrared photodetection. © 2017 American Chemical Society.

2016, Kessler, Monty, Godemann, Christian, Spannenberg, Anke, Beweries, Torsten

The crystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand are reported, namely [di-methylbis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κ2O,O')titanium(III) toluene monosolvate, [Ti(CF3O3S)(C20H30Si)]·C7H8, 1, and chlorido-[di-methyl-bis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κO)titanium(IV), [Ti(CF3O3S)(C20H30Si)Cl], 2. Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetra-hedral geometry, with the tri-fluoro-methane-sulfonate anion acting as a bidentate or monodentate ligand in 1 and 2, respectively. In 1, weak π-π stacking inter-actions involving the toluene solvent mol-ecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed.

2015, Alebrahim, M.A., Krafft, C., Popp, J., El-Khateeb, Mohammad Y.

The structure and chemical features of the human dentin enamel junction (DEJ) were characterized using Raman spectroscopic imaging. Slices were prepared from 10 German, and 10 Turkish teeth. Raman images were collected at 785 nm excitation and the average Raman spectra were calculated for analysis. Univariate and multivariate spectral analysis were applied for investigation. Raman images were obtained based on the intensity ratios of CH at 1450 cm-1 (matrix) to phosphate at 960 cm-1 (mineral), and carbonate to phosphate (1070/960) ratios. Different algorithms (HCA, K-means cluster and VCA) also used to study the DEJ. The obtained results showed that the width of DEJ is about 5 pm related to univariate method while it varies from 6 to 12 μm based on multivariate spectral technique. Both spectral analyses showed increasing in carbonate content inside the DEJ compared to the dentin, and the amide I (collagen) peak in dentin spectra is higher than DEJ spectra peak.