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Schmidt S.,Institute for Macromolecular Chemical | Schmidt S.,Albert Ludwigs University of Freiburg | Ritter B.S.,Institute for Macromolecular Chemical | Kratzert D.,Institute for Inorganic and Analytical Chemistry | And 4 more authors.
Macromolecules | Year: 2016

Glycerol serves as the exclusive bio feedstock for the preparation of high purity sorbitol tricarbonate (STC) as new intermediate for poly(carbohydrate-urethane) thermosets and 100% bio-based non-isocyanate polyhydroxyurethane (NIPU) coatings. In this process, glycerol-based acrolein is dimerized, carbonated, and oxidized, thus producing the highly reactive diepoxy functional ethylene carbonate (DOC), which by facile chemical CO2 fixation yields high purity STC. Opposite to most state-of-the-art multifunctional five-membered cyclic carbonates and regardless of the feedstock used for its manufacture, STC enables amine curing at ambient temperature even in the absence of catalysts. According to FT-IR and NMR spectroscopic analyses of the amine/carbonate reaction kinetics, the internal cyclic carbonate group is 3 times more reactive with respect to the two terminal carbonate groups. This is attributed to the electron-withdrawing effect of terminal cyclic carbonates. Curing STC with a blend of bio-based flexible and rigid diamines such as dimer fatty acid-based diamine (Priamine 1074) and isophorone diamine affords poly(carbohydrate-urethane) thermosets and NIPU coatings exhibiting substantially improved thermal and mechanical properties. © 2016 American Chemical Society.


Schmale K.,Institute for Inorganic and Analytical Chemistry | Barthel J.,Jülich Research Center | Bernemann M.,Institute for Inorganic and Analytical Chemistry | Grunebaum M.,Institute for Inorganic and Analytical Chemistry | And 4 more authors.
Journal of Solid State Electrochemistry | Year: 2013

In this work, fresh and CO2-exposed specimens of Ba 0.5Sr0.5Co0.8Fe0.2O 3-δ (BSCF) are examined by atomic force microscopy (AFM) using amplitude-modulated Kelvin probe force microscopy (KPFM) and also electrostatic force microscopy (EFM) to characterize the early stages of the formation of reaction products due to reaction with gaseous CO2. A comparison is made with results from electron microscopy on the same samples. BSCF specimens exposed for 24 and 240 h to an atmosphere of 99.9 % CO2 at 900 C, respectively, were analyzed and compared with non-exposed specimens. The observation of interconnected carbonate islands on BSCF forming a continuous carbonate layer after some exposure to CO2 indicates a Stranski-Krastanov or Volmer-Weber growth mechanism of the carbonate layer. Our results demonstrate that the measurement of surface potential variations by means of KPFM and EFM constitutes a very sensitive technique to detect the formation of reaction layers on gas permeation membranes such as BSCF. In contrast to electron microscopy techniques, scanning probe techniques permit the investigation of the topography and of electrochemical characteristics of the sample surface as received and without further preparation. © 2013 Springer-Verlag Berlin Heidelberg.


Wagner A.C.,Institute for Inorganic and Analytical Chemistry | Croll A.,Institute for Geo and Environmental Natural science | Croll A.,Albert Ludwigs University of Freiburg | Hillebrecht H.,Institute for Inorganic and Analytical Chemistry | Hillebrecht H.,Albert Ludwigs University of Freiburg
Journal of Crystal Growth | Year: 2016

The availability of suitable feed rods for Si-Ge bulk crystal growth is known to be a limiting factor in floating zone growth and other growth techniques. In this work, three Si-rich SiGe single crystals were crystallized by an optical floating zone technique in a double ellipsoid mirror furnace. The feed rods were prepared by pre-synthesis in the Spark Plasma Sintering (SPS) process starting with powders of different compositions. In a detailed section the preparation method of consolidation by mechanical alloyed powders to feed rods will be given. Results from two growth experiments starting with uniform compositions with 11 at% and 20 at% germanium as well as a zone leveling experiment with a segmented feed rod consisting of a starting zone with 32 at% Ge will be discussed. The latter experiment resulted in a crystal with nearly no axial segregation. © 2016 Published by Elsevier B.V.


Wagner A.C.,Institute for Inorganic and Analytical Chemistry | Croll A.,Albert Ludwigs University of Freiburg | Gonik M.A.,Center for Material Researches | Hillebrecht H.,Institute for Inorganic and Analytical Chemistry | And 2 more authors.
Journal of Crystal Growth | Year: 2014

In this work we made a first attempt to grow Si1-xGexsingle crystals by the so called modified float zone technique [1], without contact of container walls, using a modified AHP (axial heat flux close to the phase interface) heater. This method was derived from the "modified Bridgman" technique using a submerged heater [2]. Some advantages of this method are the improvement in crystal quality [3,4], the reduction of the radial temperature gradient and with it the reduced radial segregation during the growth experiment. For comparison another Si1-xGexcrystal was grown by the conventional float zone method, using a residual spark plasma sintered feed rod from the initially described growth experiment. Spark plasma sintering is a synthesis and consolidation technique using a pulsed current and an axial pressure to activate the sintering process [5]. Both samples were characterized by EDX, ICM, Raman and Photoluminescence spectroscopy for the purpose of analyzing the crystal quality. The use of spark plasma sintered raw material as feed material was investigated. © 2013 Elsevier B.V.


Rupp A.B.A.,Institute for Inorganic and Analytical Chemistry | Rupp A.B.A.,Albert Ludwigs University of Freiburg | Welle S.,Institute for Inorganic and Analytical Chemistry | Klose P.,Institute for Inorganic and Analytical Chemistry | And 3 more authors.
ChemPhysChem | Year: 2015

Several ionic liquids (ILs) comprising [B(hfip)4]- [hfip=OCH(CF3)2] or [Al(hfip)4]- anions and imidazolium or ammonium cations were prepared and mixed with up to 270 mol% of dimethyl carbonate (DMC). The viscosities, conductivities, and self-diffusion constants of these mixtures and, where possible, of the neat ILs were measured and compared with common [NTf2]- based ILs and their mixtures with DMC. A tremendous decrease of the viscosities and a likewise increase of the conductivities and diffusion constants can be achieved for all classes of ILs. However, the order of the conductivities is partially reversed in the diffusion data. This is probably due to the low dielectric constant of DMC and the, thus, favored ion pairing, as evidenced, for example, by the calculated ionicities. Altogether, our data show that the chemically robust, but high-melting and more viscous [B(hfip)4]- ILs might be candidates for electrolytes when mixed with suitable molecular solvents. Less is more: An study of the viscosities, conductivities, and self-diffusion constants of mixtures of dimethyl carbonate (DMC) with a variety of ionic liquids with highly fluorinated anions reveals a severe decrease of the amount of free charge carriers with increasing DMC content (see picture). However, owing to a reduction of the viscosity, the mixtures are more conductive than neat ionic liquids and open the possibility of using high-melting [B(OCH(CF3)2)4]- salts as electrolytes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Rupp A.B.A.,Albert Ludwigs University of Freiburg | Welle S.,Institute for Inorganic and Analytical Chemistry | Klose P.,Institute for Inorganic and Analytical Chemistry | Scherer H.,Institute for Inorganic and Analytical Chemistry | Krossing I.,Albert Ludwigs University of Freiburg
ChemPhysChem | Year: 2015

Several ionic liquids (ILs) comprising [B(hfip)4]- [hfip=OCH(CF3)2] or [Al(hfip)4]- anions and imidazolium or ammonium cations were prepared and mixed with up to 270mol% of dimethyl carbonate (DMC). The viscosities, conductivities, and self-diffusion constants of these mixtures and, where possible, of the neat ILs were measured and compared with common [NTf2]- based ILs and their mixtures with DMC. A tremendous decrease of the viscosities and a likewise increase of the conductivities and diffusion constants can be achieved for all classes of ILs. However, the order of the conductivities is partially reversed in the diffusion data. This is probably due to the low dielectric constant of DMC and the, thus, favored ion pairing, as evidenced, for example, by the calculated ionicities. Altogether, our data show that the chemically robust, but high-melting and more viscous [B(hfip)4]- ILs might be candidates for electrolytes when mixed with suitable molecular solvents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Becker T.,Max Planck Institute for Chemical Ecology | Gorls H.,Institute for Inorganic and Analytical Chemistry | Pauls G.,Max Planck Institute for Chemical Ecology | Wedekind R.,Max Planck Institute for Chemical Ecology | And 3 more authors.
Journal of Organic Chemistry | Year: 2013

A novel synthetic route was developed for the construction of isoxazolin-5-one glucosides using a cascade reaction. An X-ray crystal structure analysis of a isoxazolin-5-one glucoside confirmed the structure and stereochemistry of the heterocycle. The properties of the α- and β-anomers of the isoxazolin-5-one glucosides were compared. The first synthesis of 2-[6′-(3″-nitropropanoyl)-β-d-glucopyranosyl]-3- isoxazolin-5-one was realized by direct enzymatic esterification without need of further protective groups. © 2013 American Chemical Society.


Kuhlisch C.,Institute for Inorganic and Analytical Chemistry | Deicke M.,Institute for Inorganic and Analytical Chemistry | Ueberschaar N.,Institute for Inorganic and Analytical Chemistry | Wichard T.,Institute for Inorganic and Analytical Chemistry | Pohnert G.,Institute for Inorganic and Analytical Chemistry
Limnology and Oceanography: Methods | Year: 2016

Polyunsaturated aldehydes (PUAs) are a group of microalgal metabolites that have attracted a lot of attention due to their biological activity. Determination of PUAs has become an important routine procedure in plankton and biofilm investigations, especially those that deal with chemically mediated interactions. Here we introduce a fast and direct derivatization free method that allows quantifying PUAs in the nanomolar range, sufficient to undertake the analysis from cultures and field samples. The sample preparation requires one simple filtration step and the initiation of PUA formation by cell disruption. After centrifugation the samples are ready for measurement without any further handling. Within one chromatographic run this method additionally allows us to monitor the formation of the polar oxylipins arising from the cleavage of precursor fatty acids. The robust method is based on analyte separation and detection using ultra high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (UHPLC-APCI MS) and enables high throughput investigations by employing an analysis time of only 5 min. Our protocol thus provides an alternative and extension to existing PUA determinations based on gas chromatography-mass spectrometry (GC-MS) with shorter run times and without any chemical derivatization. It also enables researchers with widely available LC-MS analytical platforms to monitor PUAs. Additionally, non-volatile oxylipins such as ω-oxo-acids and related compounds can be elucidated and monitored. © 2016 Association for the Sciences of Limnology and Oceanography.


Schmidt P.,Lausitz University of Applied Science | Schoneich M.,TU Dresden | Bawohl M.,Institute for Inorganic and Analytical Chemistry | Nilges T.,TU Munich | Weihrich R.,University of Regensburg
Journal of Thermal Analysis and Calorimetry | Year: 2012

Several methods are established in thermal analysis to investigate phase formation, phase transition, and decomposition reactions. The analysis of phase equilibria with volatile components is particularly feasible by using standard method of thermogravimetry. Hardly any investigations of phase formation reactions are possible to realize if one of the components is lost by vaporization. By using the "High-Temperature Gas-Balance" (HTGB), the vapor phase is enclosed in a silica ampoule and thus forms an equilibrium gas phase in permanent contact with the solid phase. The measurement signal δmmeas is caused by change of the leverage of the horizontal balance support during evaporation and condensation. The application of the HTGB allows the analysis of solid-gas equilibria in the working range from 0.01 till 15 bar at temperatures up to 1,100 °C. The first comparison of evaporation reactions determined by standard thermogravimetric analyses and by measurements using the HTGB is given for the inorganic systems: P, As, SeO2, PtI2, and Hg/I. © Akadémiai Kiadó, Budapest, Hungary 2011.


PubMed | Institute for Inorganic and Analytical Chemistry
Type: Journal Article | Journal: Chemphyschem : a European journal of chemical physics and physical chemistry | Year: 2015

Several ionic liquids (ILs) comprising [B(hfip)4 ](-) [hfip=OCH(CF3 )2 ] or [Al(hfip)4 ](-) anions and imidazolium or ammonium cations were prepared and mixed with up to 270 mol% of dimethyl carbonate (DMC). The viscosities, conductivities, and self-diffusion constants of these mixtures and, where possible, of the neat ILs were measured and compared with common [NTf2 ](-) based ILs and their mixtures with DMC. A tremendous decrease of the viscosities and a likewise increase of the conductivities and diffusion constants can be achieved for all classes of ILs. However, the order of the conductivities is partially reversed in the diffusion data. This is probably due to the low dielectric constant of DMC and the, thus, favored ion pairing, as evidenced, for example, by the calculated ionicities. Altogether, our data show that the chemically robust, but high-melting and more viscous [B(hfip)4 ](-) ILs might be candidates for electrolytes when mixed with suitable molecular solvents.

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