TY  - THES
A1  - Lämmermann, Anica
T1  - Anwendung von Substituenteneffekten zur Strukturaufklärung mittels NMR-Spektroskopie und Moleculare Modelling
Y1  - 2010
CY  - Potsdam
ER  - 
TY  - THES
A1  - Kühnle, Hans-Jochen
T1  - Modifizierte Polymer-Peptid-Konjugate : Regulative Strategien für die Mikrostrukturbildung und Anwendung
Y1  - 2010
CY  - Potsdam
ER  - 
TY  - THES
A1  - Cui, Jing
T1  - Preparation of medical grade, amorphous polymer systems with adjustable stiffness and development of self- surfficiently moving model scaffolds based on shape-memory polymer composites
Y1  - 2010
CY  - Potsdam
ER  - 
TY  - THES
A1  - Eidner, Sascha
T1  - Lanthanoide als Luminezenzsonden in aquatischen Systemen : Modellsysteme zur Beschreibung der Wechselwirkungen von Metallionen mit natürlicher organischer Materie
Y1  - 2010
CY  - Potsdam
ER  - 
TY  - THES
A1  - Chanana, Munish
T1  - Synthesis of stimuli-responsive and switchable inorganic nanoparticles for biomedical applications
Y1  - 2010
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Matthes, Annika
A1  - Schilde, Uwe
T1  - Crystal structure of 3,4-diacetyl-15,21-dioxatetracyclo- [23.4.0.02,7.06,11]nonacosa-1(29),2,4,6,8,10,25,27- octaene- 14,22-dioneùwater (1:2), C31H32O6 · 2H2O
Y1  - 2010
UR  - ftp://ftp.oldenbourg.de/pub/download/frei/ncs/225-4/1267-3146.pdf
SN  - 1433-7266
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Werner, Frank
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
T1  - The reaction of 3,4-dihydro-2H-pyran with oxalyl chloride : formation and crystal structure analysis of an unexpected bicyclic product
N2  - 3,4-Dihydro-2-H-pyran and oxalyl chloride react, depending on the conditions, to keto esters, a pyran-3- carboxylic acid or derivatives thereof, or to an hitherto unknown bicyclic acetal containing a vinyl chloride moiety. The structure of the latter product has been unambiguously elucidated by single-crystal X-ray structure analysis. A mechanism for its formation is proposed.
Y1  - 2010
UR  - 1960 = dx.doi.org/10.1002/jhet.456
SN  - 0022-152X
ER  - 
TY  - JOUR
A1  - Kuke, S.
A1  - Marmodee, Bettina
A1  - Eidner, Sascha
A1  - Schilde, Uwe
A1  - Kumke, Michael Uwe
T1  - Intramolecular deactivation processes in complexes of salicylic acid or glycolic acid with Eu(III)
N2  - The complexation of Eu(III) by 2-hydroxy benzoic acid (2HB) or glycolic acid (GL) was investigated using steady- state and time-resolved laser spectroscopy. Experiments were carried out in H2O as well as in D2O in the temperature range of View the MathML source. The Eu(III) luminescence spectra and luminescence decay times were evaluated with respect to the temperature dependence of (i) the luminescence decay time ;, (ii) the energy of the View the MathML source transition, (iii) the width of the View the MathML source transition, and (iv) the asymmetry ratio calculated from the luminescence intensities of the View the MathML source and View the MathML source transition, respectively. The differences in ligand-related luminescence quenching are discussed. Based on the temperature dependence of the luminescence decay times an activation energy for the ligand-specific non-radiative deactivation in Eu(III)-2HB or Eu(III)-GL complexes was determined. It is stressed that ligand-specific quenching processes (other than OH quenching induced by water molecules) need to be determined and considered in detail, in order to extract speciation- relevant information from luminescence data (e.g., estimation of the number of water molecules nH2O in the first coordination sphere of Eu(III)). In case of 2HB, conclusions drawn from the evaluation of the Eu(III) luminescence are compared with results of a X-ray structure analysis.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/article/pii/S1386142510000144
SN  - 0584-8539
ER  - 
TY  - JOUR
A1  - Starke, Ines
A1  - Kammer, Stefan
A1  - Holdt, Hans-Jürgen
A1  - Kleinpeter, Erich
T1  - Stability of disubstituted copper complexes in the gas phase analyzed by electrospray ionization mass spectrometry
N2  - A series of nitrogen ligand (L)/copper complexes of the type [(CuL)-L-I](+), [(CuL)-L-II(X)](+) and [(CuL2)-L- I](+) (X = Cl-, BF4-, acac(-), CH3COO- and SO3CF3-) was studied in the gas phase by electrospray ionization mass spectrometry. The following ligands (L) were employed: 1,12-diazaperylene (dap), 1,1'-bisiso-quinoline (bis), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 2,11-disubstituted 1,12-diazaperylenes (dap), 3,3'- disubstituted 1,1'-bisisoquinoline (bis), 5,8-dimethoxy-substituted diazaperylene (meodap), 6,6'-dimethoxy- substituted bisisoquinoline (meobis) and 2,9-dimethyl-1,10-phenanthroline (dmphen). Collision-induced decomposition measurements were applied to evaluate the relative stabilities of the different copper complexes. The influence of the spatial arrangement of the ligands, of the type of substituents and of the counter ion of the copper salts employed for the complexation was examined. Correlations were found between the binding constants of the [ML2](+) complexes in solution and the relative stabilities of the analogous complexes in the gas phase. Furthermore, complexation with the ligands 2,11-dialkylated 1,12-diazaperylenes [alkyl = ethyl (dedap) and isopropyl (dipdap)] was studied in the solvents CH3OH and CH3CN.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/4849
U6  - https://doi.org/10.1002/Rcm.4519
SN  - 0951-4198
ER  - 
TY  - THES
A1  - Huber, Christian
T1  - Explizit zeitabhängige Configuration-Interaction-Singles und Coupled-Cluster-Singles-Doubles Rechnungen zur laserinduzierten Vielelektronendynamik
Y1  - 2010
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Hass, Roland
A1  - Munzke, Dorit
A1  - Reich, Oliver
T1  - Inline-Partikelgroeßenmesstechniken fuer Suspensionen und Emulsionen
N2  - Die Inline-Bestimmung von Teilchengroeßen in Emulsionen und Suspensionen stellt besondere Anforderungen an die Messtechnik, da auch bei sehr hohen Teilchenkonzentrationen im Prozess verduennungsfreie Analytik betrieben werden soll. Neben einer Klaerung der Begriffe atline, online und in-line gibt der Beitrag eine Einfuehrung in die mathematische Beschreibung von Groeßenverteilungen. Als Inline-Techniken werden Photonendichtewellen-Spektroskopie, Focused Beam Reflectance Measurement und Ultraschallextinktion-Spektroskopie diskutiert und ihre sehr unterschiedlichen physikalischen Messprinzipien erlaeutert. Auch wird kurz erklaert, wie Teilchengroeßen aus den Messresultaten erhalten werden. Die wesentlichen Charakteristika dieser drei Methoden werden abschließend im ueberblick dargestellt.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/60500203/
U6  - https://doi.org/10.1002/cite.200900172
SN  - 0009-286X
ER  - 
TY  - JOUR
A1  - Harms, Stephan
A1  - Raetzke, Klaus
A1  - Faupel, Franz
A1  - Egger, Werner
A1  - Ravello, Lori Boyd de
A1  - Laschewsky, André
A1  - Wang, Weinan
A1  - Müller-Buschbaum, Peter
T1  - Free volume and swelling in thin films of poly(n-isopropylacrylamide) end-capped with n-butyltrithiocarbonate
N2  - The free volume in thin films of poly(N-isopropylacrylamid) end-capped with n-butyltrio-carbonate (nbc-PNIPAM) is probed with positron annihilation lifetime spectroscopy (PALS). The PALS measurements are performed as function of energy to obtain depth profiles of the free volume of nbc-PNIPAM films. The range of nbc-PNIPAM films with thicknesses from 40 to 200 nm is focused. With decreasing film thickness the free volume increases in good agreement with an increase in the maximum swelling capability of the nbc-PNIPAM films. Thus in thin hydrogel films the sorption and swelling behavior is governed by free volume.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/10003270
U6  - https://doi.org/10.1002/marc.201000067
SN  - 1022-1336
ER  - 
TY  - JOUR
A1  - Haase, Martin F.
A1  - Grigoriev, Dmitry
A1  - Moehwald, Helmuth
A1  - Tiersch, Brigitte
A1  - Shchukin, Dmitry G.
T1  - Encapsulation of amphoteric substances in a pH-sensitive pickering emulsion
N2  - Oil-in-water (o/w) Pickering emulsions stabilized with silica nanoparticles were prepared. Droplets of diethyl phthalate (oil phase) act as reservoirs for 8-hydroxyquinoline (8-HQ), which is used as (a) the hydrophobizing agent for the silica particles and (b) an encapsulated corrosion inhibitor for application in active feedback coatings. The hydrophobization of silica nanoparticles with 8-HQ is determined by the amount of this agent adsorbed on the nanoparticle surface. The latter is governed by the 8-HQ concentration in the aqueous phase, which in turn depends on the degree of protonation and fir ally on the pH. We observe three ranges of 8-HQ adsorption value with respect to nanoparticle hydophobization: (I) insufficient, (2) sufficient, and (3) excessive adsorption by the formation of an 8-HQ bilayer, where only case 2 leads to the necessary nanoparticle hydrophobization. Hence emulsions stable in a narrow pH window between pH 5.5 and 4.4 follow. Here functional molecules are sufficiently charged to compensate for the charges on silica nanoparticles to make them interfacially active and thus able to stabilize an emulsion but they are still to a large extent uncharged and thereby remain in the oil phase. The emulsification is reversible upon changing the pH to a value beyond the stability region.
Y1  - 2010
UR  - http://pubs.acs.org/journal/jpccck
U6  - https://doi.org/10.1021/Jp104052s
SN  - 1932-7447
ER  - 
TY  - JOUR
A1  - Glatzel, Stefan
A1  - Badi, Nezha
A1  - Paech, Michael
A1  - Laschewsky, André
A1  - Lutz, Jean-Francois
T1  - Well-defined synthetic polymers with a protein-like gelation behavior in water
N2  - Homopolymers of N-acryloyl glycinamide were prepared by reversible addition-fragmentation chain transfer polymerization in water. The formed macromolecules exhibit strong polymer-polymer interactions in aqueous milieu and therefore form thermoreversible physical hydrogels in pure water, physiological buffer or cell medium.
Y1  - 2010
UR  - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CC
U6  - https://doi.org/10.1039/C0cc00038h
SN  - 1359-7345
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Novel anthracene materials for applications in lithography and reversible photoswitching by light and air
N2  - Herein we demonstrate how the photoreaction between anthracenes and singlet oxygen (O-1(2)) is employed for applications either as photoswitch or as photoresist. Thin Films of the diaryl-alkyl anthracene 1 and the analogous oligomeric species 2 were it-radiated under photomasks to generate pattern structures composed of 1/1-O-2 and 2/2-O-2. Kelvin probe force microscopy (KPFM) provided a powerful and nondestructive method to image the pattern information. The following studies based on AFM, KPFM and contact angle measurements unfold that the two species 1 and 2 underwent different progressions after the imaging step. Degrading is observed for the monomeric compound 1 and the pattern eventually becomes recognizable in topography. In the oxidized state (1-O-2) the monomeric species remains physically stable. In consequence, the unreacted portion is removable and the remaining oxygenated form 1-O-2 is sufficiently stable to protect in underlying substrate (e.g., silver) from etching. Thus, the system 1/1-O-2 operates as photoresist. Oil the other hand, both states of the oligomier 2 remain stable. The Film is stable up to temperatures > 120 degrees C required to erase the pattern within acceptable time by cycloreversion. Anthracene 2 therefore acts as erasable and rewritable photochromic switch. The different behavior between 1 and 2 is explained by phase transitions which cause crystallization and finally ablation. Such transitions affect only the monomeric system 1/1-O-2 and not the oligomeric system 2/2-O-2. In conclusion, we designed two very similar materials based on diarylanthracenes, which can act either as a photoresist or as a rewritable photochrornic switch.
Y1  - 2010
UR  - http://pubs.acs.org/journal/langd5
U6  - https://doi.org/10.1021/La904299n
SN  - 0743-7463
ER  - 
TY  - JOUR
A1  - Füchsel, Gernot
A1  - Klamroth, Tillmann
A1  - Tremblay, Jean Christophe
A1  - Saalfrank, Peter
T1  - Stochastic approach to laser-induced ultrafast dynamics : the desorption of H-2/D-2 from Ru(0001)
N2  - The desorption of molecular hydrogen and deuterium induced by femtosecond-laser pulses is studied theoretically for the so-called DIMET (Desorption Induced by Multiple Electronic Transitions) process. These investigations are based on nonadiabatic classical Monte Carlo trajectory (CMCT) simulations on a ground and an excited state potential energy surface, including up to all six adsorbate degrees of freedom. The focus is on the hot-electron mediated energy transfer from the surface to the molecule and back, and the energy partitioning between the different degrees of freedom of the desorbing molecules. We first validate for a two-mode model comprising the desorption mode and the internal vibrational coordinate, the classical Monte Carlo trajectory method by comparing with Monte Carlo wavepacket (MCWP) calculations arising from a fully quantum mechanical open-system density matrix treatment. We then proceed by extending the CMCT calculations to include all six nuclear degrees of freedom of the desorbing molecule. This allows for a detailed comparison between theory and experiment concerning isotope effects, energy partitioning (translational, vibrational, and rotational energies and their distributions), and the dependence of these properties on the laser fluence. The most important findings are as follows. (i) CMCT agrees qualitative with the MCWP scheme. (ii) The basic experimental features such as the large isotope effect, the non-linear increase of yield with laser fluence, translationally hot products (in the order of several 1000 K) and non-equipartitioning of translational and internal energies (E-trans > E- vib > E-rot) are well reproduced. (iii) Predictions concerning a strong angular dependence of translational energies at large observation angles are also made.
Y1  - 2010
UR  - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CP
U6  - https://doi.org/10.1039/C0cp00895h
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Fokou, Patrice A.
A1  - Meier, Michael A. R.
T1  - Studying and suppressing olefin isomerization side reactions during ADMET polymerizations
N2  - Olefin isomerization side reactions that occur during ADMET polymerizations were studied by preparing polyesters via ADMET and subsequently degrading these polyesters via transesterification with methanol. The resulting diesters, representing the repeating units of the previously prepared polyesters, were then analyzed by GC-MS. This strategy allowed quantification of the amount of olefin isomerization that took place during ADMET polymerization with second generation ruthenium metathesis catalysts. In a second step, it was shown that the addition of benzoquinone to the polymerization mixture prevented the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts may now be used for the preparation of well-defined polymers via ADMET with very little isomerization, which was not possible before.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/10003270
U6  - https://doi.org/10.1002/marc.200900678
SN  - 1022-1336
ER  - 
TY  - JOUR
A1  - Fettke, Anja
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - Lectin-bound conformations and non-covalent interactions of glycomimetic analogs of thiochitobiose
N2  - The bound conformations of five S-glycoside analogs of N,N'-diacetylchitobiose as well as their non- covalent interactions with two lectins, Phytolacca americana lectin (PAL) and wheat germ agglutinin (WGA), are reported. The conformations of the ligands were examined by trNOESY experiments and compared with the free, solution-state conformations and molecular modeling data obtained by force field calculations. In the case of S-aryl, S-glycosides with exclusively S-glycosidic linkages, similar free and lectin-bound conformations and non-covalent interactions were found, whereas they differed for mixed glycosides and for a thiazoline derivative. In addition, STD (saturation transfer difference) NMR magnetization transfer efficiencies at three different temperatures were determined and assessed with respect to the structural differences of these pseudosaccharides. The binding epitopes of each substrate with PAL and WGA were also determined.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2010.04.012
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Fechner, Mabya
A1  - Kosmella, Sabine
A1  - Koetz, Joachim
T1  - pH-dependent polyampholyte SDS interactions
N2  - Aqueous solutions of sodium dodecylsulfate (SDS) and poly(N,N'-diallyl-N,N'-dimethyl-alt-maleamic carboxylate) (PalH), a synthetic pH-tuneable polyelectrolyte (PEL), have been investigated by various techniques at different pH-values in absence and presence of NaCl. Potentiometric measurements using a surfactant-selective electrode indicate a quite complex interaction mechanism, which can be subdivided into different regions, where non-cooperative, electrostatic and cooperative hydrophobic interactions are of relevance. It was concluded, that in dependence on pH, conformational changes are responsible for the different interaction behavior in the NaCl-free system. Isothermal titration calorimetry (ITC) suggests that early stage hydrophobic binding is an exothermic process followed by electrostatic interactions, which are endothermic in nature and entropy driven. After NaCl addition the interaction mechanism becomes independent of pH due to a screening of (i) attractive interactions between the surfactant head groups and oppositely charged binding sites and (ii) repulsive forces between the surfactant head groups. Furthermore, the ITC investigations have revealed that after salt-addition surfactant micelles interact with the polymer instead of separated SDS molecules due to a depression of the CMC.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00219797
U6  - https://doi.org/10.1016/j.jcis.2010.01.092
SN  - 0021-9797
ER  - 
TY  - JOUR
A1  - Fandrich, Nick
A1  - Falkenhagen, Jana
A1  - Weidner, Steffen M.
A1  - Staal, Bastiaan
A1  - Thuenemann, Andreas F.
A1  - Laschewsky, André
T1  - Characterization of new amphiphilic block copolymers of N-vinylpyrrolidone and vinyl acetate, 2-chromatographic separation and analysis by MALDI-TOF and FT-IR coupling
N2  - PVP-block-PVAc block copolymers were synthesized by controlled radical polymerization applying a RAFT/MADIX system and were investigated by HPLC and by coupling of chromatography to FT-IR spectroscopy and MALDI-TOF MS. Chromatographic methods (LACCC and gradient techniques) were developed that allowed a separation of block copolymers according to their repeating units. The results of the spectroscopic and spectrometric analysis clearly showed transfer between radicals and process solvent. With the use of hyphenated techniques differences between main and side products were detected. In agreement with previously published results, obtained by NMR, SEC, static light scattering and MALDI- TOF MS, our data proved a non-ideal RAFT polymerization.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/10003495/home
U6  - https://doi.org/10.1002/macp.201000044
SN  - 1022-1352
ER  - 
TY  - JOUR
A1  - Fandrich, Nick
A1  - Falkenhagen, Jana
A1  - Weidner, Steffen M.
A1  - Pfeifer, Dietmar
A1  - Staal, Bastiaan
A1  - Thuenemann, Andreas F.
A1  - Laschewsky, André
T1  - Characterization of new amphiphilic block copolymers of N-vinyl pyrrolidone and vinyl acetate, 1-analysis of copolymer composition, end groups, molar masses and molar mass distributions
N2  - New amphiphilic block copolymers consisting of N-vinyl pyrrolidone and vinyl acetate were synthesized via controlled radical polymerization using a reversible addition/fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) system. The synthesis was carried out in 1,4-dioxane as process solvent. In order to get conclusions on the mechanism of the polymerization the molecular structure of formed copolymers was analysed by means of different analytical techniques. C-13 NMR spectroscopy was used for the determination of the monomer ratios. End groups were analysed by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This technique was also used to determine possible fragmentations of the RAFT end groups. By means of a combination of size exclusion chromatography, C-13 NMR and static light scattering molar mass distributions and absolute molar masses could be analysed. The results clearly show a non-ideal RAFT mechanism.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/10003495/home
U6  - https://doi.org/10.1002/macp.200900466
SN  - 1022-1352
ER  - 
TY  - JOUR
A1  - Diehl, Christina
A1  - Cernoch, Peter
A1  - Zenke, Ingrid
A1  - Runge, Heike
A1  - Pitschke, Rona
A1  - Hartmann, Juergen
A1  - Tiersch, Brigitte
A1  - Schlaad, Helmut
T1  - Mechanistic study of the phase separation/crystallization process of poly(2-isopropyl-2-oxazoline) in hot water
N2  - The kinetics of the crystallization of thermoresponsive poly(2-isopropyl-2-oxazoline) in water and the time- dependent evolution of the morphology were examined using wide-angle X-ray scattering and conventional and cryogenic scanning electron microscopy. Results indicate that a temperature-induced phase separation produces a bicontinuous polymer network-like structure, which with the onset of crystallization collapses into individual particles (1-2 mu m in diameter) composed of a porous fiber mesh. Nanofibers then preferentially form at the particle surface, thus wrapping the microspheres like a ball of wool. The particle morphology is severely affected by changes in temperature and less by the initial polymer concentration.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/sm/index.asp
U6  - https://doi.org/10.1039/C0sm00114g
SN  - 1744-683X
ER  - 
TY  - JOUR
A1  - de Espinosa, Lucas Montero
A1  - Meier, Michael A. R.
A1  - Ronda, Juan C.
A1  - Galiß, Marina
A1  - Cßdiz, Virginia
T1  - Phosphorus-containing renewable polyester-polyols via ADMET polymerization : synthesis, functionalization, and radical crosslinking
N2  - An alpha,omega-diene containing hydroxyl groups was prepared from plant oil-derived platform chemicals. The acyclic diene metathesis copolymerization (ADMET) of this monomer with a phosphorus-containing alpha,omega-cliene (DOPO II), also plant oil derived, afforded a series of phosphorus containing linear polyesters, which have been fully characterized. The backbone hydroxyls of these polyesters have been acrylated and radically polymerized to produce crosslinked polymers. The thermomechanical and mechanical properties, the thermal stability, and the flame retardancy of these phosphorus-based thermosets have been studied. Moreover, methyl 10-undecenoate has been used as chain stopper in selected ADMET polymerizations to study the effect of the prepolymers' molecular weights on the different properties of the final materials.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/117932467/tocgroup
U6  - https://doi.org/10.1002/Pola.23887
SN  - 0887-624X
ER  - 
TY  - JOUR
A1  - de Araujo, Martha T.
A1  - Chacon, Eluzir P.
A1  - Carneiro, José W. de M.
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Analysis of anisotropic effects in trinuclear metal carbonyl compounds by visualization of through-space NMR shielding
N2  - Through-space NMR shieldings were calculated for trinuclear metal-carbonyl compounds [M-3(CO)(12)] (M = Fe, Ru, Os), employing the nucleus-independent chemical shift approach. The through-space shieldings were visualized as a contour plot of iso-chemical shielding surfaces, and were applied to quantify the overall anisotropic effect of the carbonyl groups, as well as to identify the influence of the transition metal on the scopes of the corresponding anisotropy cones. The shielding surfaces show that the anisotropic effect of the carbonyl groups at equatorial positions changes depending on the metal. This effect was associated with pi-backdonation from the metal to the carbonyl groups in that position, in agreement with geometric data as well as calculated NMR parameters. Therefore, visualization of the through-space NMR shieldings of trinuclear metal-carbonyl compounds of group 8 is able to reflect the distinct arrangements of the carbonyl groups in these organometallic compounds.
Y1  - 2010
UR  - http://www.springerlink.com/content/100529
U6  - https://doi.org/10.1007/s00894-010-0662-3
SN  - 1610-2940
ER  - 
TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Idzik, Krzysztof R.
A1  - Cranfield, Charles G.
A1  - Beckert, Rainer
A1  - Mohr, Gerhard J.
T1  - Synthesis and sensing properties of a new carbazole fluorosensor for detection of abacavir
N2  - An abacavir-targeted fluorosensor based on the carbazole moiety has been synthesised and characterised. Recognition of abacavir is by base pairing between a uracil moiety present in the fluorosensor and the guanine moiety of abacavir. The fluorosensor exhibits five-fold quenching in the presence of 50M abacavir. Its sensitivity to abacavir is superior to that of other reverse transcriptase inhibitors: zidovudine, lamivudine and didanosine. Due to its high sensitivity, this fluorosensor has the potential to be used in multi-analyte array-based detection platforms as well as in microfluidics systems.
Y1  - 2010
UR  - http://www.informaworld.com/openurl?genre=journal&issn=1061-0278
U6  - https://doi.org/10.1080/10610278.2010.506541
SN  - 1061-0278
ER  - 
TY  - JOUR
A1  - Coy, Ericsson D.
A1  - Jovanovic, Ljubisa
A1  - Sefkow, Michael
T1  - One-pot, Pd-catalyzed synthesis of trans-dihydrobenzofurans from o-aminophenols
N2  - An efficient and facile synthesis of trans-dihydrobenzofurans has been accomplished from o-aminophenols and phenylpropenes via a novel (one-pot) diastereoselective Pd-catalyzed oxyarylation reaction. The development and optimization of this method is described.
Y1  - 2010
UR  - http://pubs.acs.org/journal/orlef7
U6  - https://doi.org/10.1021/Ol100433z
SN  - 1523-7060
ER  - 
TY  - JOUR
A1  - Bramborg, Andrea
A1  - Linker, Torsten
T1  - Selective synthesis of 1,4-dialkylbenzenes from terephthalic acid
N2  - Terephthalic acid reacts with alkyl halides under Birch conditions to substituted 1,4-cyclohexadienes in high yields and good stereoselectivities. Electrophiles containing ester or nitrile groups undergo a surprising fragmentation under the reaction conditions. Subsequent treatment with chlorosulfonic acid proceeds by an interesting tandem decarbonylation/decarboxylation, affording 1,4-dialkylbenzenes in excellent regioselectivity. Thus our new method is superior to classical Friedel-Crafts alkylations.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/77002176
U6  - https://doi.org/10.1002/adsc.201000322
SN  - 1615-4150
ER  - 
TY  - JOUR
A1  - Bouakline, Foudhil
A1  - Althorpe, Stuart C.
A1  - Larregaray, Pascal
A1  - Bonnet, Laurent
T1  - Strong geometric-phase effects in the hydrogen-exchange reaction at high collision energies : II. quasiclassical trajectory analysis
N2  - Recent calculations on the hydrogen-exchange reaction [Bouakline et al., J. Chem. Phys. 128, 124322 (2008)], have found strong geometric phase (GP) effects in the state-to-state differential cross-sections (DCS), at energies above the energetic minimum of the conical intersection (CI) seam, which cancel out in the integral cross-sections (ICS). In this article, we explain the origin of this cancellation and make other predictions about the nature of the reaction mechanisms at these high energies by carrying out quasiclassical trajectory (QCT) calculations. Detailed comparisons are made with the quantum results by splitting the quantum and the QCT cross-sections into contributions from reaction paths that wind in different senses around the CI and that scatter the products in the nearside and farside directions. Reaction paths that traverse one transition state (1-TS) scatter their products in just the nearside direction, whereas paths that traverse two transition states (2-TS) scatter in both the nearside and farside directions. However, the nearside 2-TS products scatter into a different region of angular phase-space than the 1-TS products, which explains why the GP effects cancel out in the ICS. Analysis of the QCT results also suggests that two separate reaction mechanisms may be responsible for the 2-TS scattering at high energies.
Y1  - 2010
UR  - http://www.informaworld.com/openurl?genre=journal&issn=0026-8976
U6  - https://doi.org/10.1080/00268971003610218
SN  - 0026-8976
ER  - 
TY  - JOUR
A1  - Borchert, Manuela
A1  - Wilke, Max
A1  - Schmidt, Christian
A1  - Rickers, Karen
T1  - Rb and Sr partitioning between haplogranitic melts and aqueous solutions
N2  - Rubidium and strontium partitioning experiments between haplogranitic melts and aqueous fluids (water or 1.16- 3.56 m (NaCl + KCl) +/- HCl) were conducted at 750-950 degrees C and 0.2-1.4 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. In addition, we studied if the applied technique (rapid and slow quench, and in-situ determination of trace element concentration in the fluid) has a bearing on the obtained data. There is good agreement of the data from different techniques for chloridic solutions, whereas back reactions between fluid and Melt upon cooling have a significant effect on results from the experiments with water. The Rb fluid-melt partition coefficient shows no recognizable dependence on melt composition and temperature. For chloridic Solutions, it is similar to 0.4, independent of pressure. In experiments with water, it is one to two orders of magnitude lower and increases with pressure. The strontium fluid-melt partition coefficient does not depend on temperature. It increases slightly with pressure in Cl free experiments. In chloridic fluids, there is a sharp increase in the Sr partition coefficient with the alumina saturation index (ASI) from 0.003 at an ASI of 0.8 to a maximum of 0.3 at an ASI of 1.05. At higher ASI, it decreases slightly to 0.2 at an ASI of 1.6. It is one to two orders of magnitude higher in chloridic fluids compared to those found in H2O experiments. The Rb/Sr ratio in non-chloridic solutions in equilibrium with metaluminous melts increases with pressure, whereas the Rb/Sr ratio in chloridic fluids is independent of pressure and decreases with fluid salinity. The obtained fluid-melt partition coefficients are in good agreement with data from natural cogenetic fluid and melt inclusions. Numerical modeling shows that although the Rb/Sr ratio in the residual melt is particularly sensitive to the degree of fractional crystallization, exsolution of a fluid phase, and associated fluid-melt partitioning is not a significant factor controlling Rb and Sr concentrations in the residual melt during crystallization of most granitoids.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00167037
U6  - https://doi.org/10.1016/j.gca.2009.10.033
SN  - 0016-7037
ER  - 
TY  - JOUR
A1  - Bivigou Koumba, Achille Mayelle
A1  - Goernitz, Eckhard
A1  - Laschewsky, André
A1  - Müller-Buschbaum, Peter
A1  - Papadakis, Christine M.
T1  - Thermoresponsive amphiphilic symmetrical triblock copolymers with a hydrophilic middle block made of poly(N- isopropylacrylamide) : synthesis, self-organization, and hydrogel formation
N2  - Several series of symmetrical triblock copolymers were synthesized by the reversible addition fragmentation chain transfer method. They consist of a long block of poly(N-isopropylacrylamide) as hydrophilic, thermoresponsive middle block, which is end-capped by two small strongly hydrophobic blocks made from five different vinyl polymers. The association of the amphiphilic polymers was studied in dilute and concentrated aqueous solution. The polymer micelles found at low concentrations form hydrogels at high concentrations, typically above 30-35 wt.%. Hydrogel formation and the thermosensitive rheological behavior were studied exemplarily for copolymers with hydrophobic blocks of polystyrene, poly(2-ethylhexyl acrylate), and poly(n-octadecyl acrylate). All systems exhibited a cloud point around 30 A degrees C. Heating beyond the cloud point initially favors hydrogel formation but continued heating results in macroscopic phase separation. The rheological behavior suggests that the copolymers associate into flower-like micelles, with only a small share of polymers that bridge the micelles and act as physical cross-linkers, even at high concentrations.
Y1  - 2010
UR  - http://www.springerlink.com/content/101551
U6  - https://doi.org/10.1007/s00396-009-2179-9
SN  - 0303-402X
ER  - 
TY  - JOUR
A1  - Biermann, Ursula
A1  - Metzger, Juergen O.
A1  - Meier, Michael A. R.
T1  - Acyclic triene metathesis oligo- and polymerization of high oleic sun flower oil
N2  - High oleic sunflower oil, a renewable raw material consisting of triglycerides with internal C=C-double bonds, was polymerized via acyclic triene metathesis (ATMET) to highly branched and functionalized polyesters. If the Hoveyda- Grubbs second generation catalyst was used and methyl acrylate was introduced as a chain stopper, the molecular weight of the obtained polymers could be tuned by varying the ratio of the triglyceride and methyl acrylate. Using the first generation Grubbs catalyst for the polymerization of high oleic sunflower oil, no cross-linking was observed, even without the use of a chain stopper. The resulting branched materials were characterized by GPC, H-1 and C-13 NMR, and ESI-MS.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/journal/10003495/home
U6  - https://doi.org/10.1002/macp.200900615
SN  - 1022-1352
ER  - 
TY  - JOUR
A1  - Baranac-Stojanovic, Marija
A1  - Klaumuenzer, Ute
A1  - Markovic, Rade
A1  - Kleinpeter, Erich
T1  - Structure, configuration, conformation and quantification of the push pull-effect of 2-alkylidene-4- thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives
N2  - Structures of a series of push-pull 2-alkylidene-4-thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives were optimized at the B3LYP/6-31G(d) level of theory in the gas phase and discussed with respect to configurational and conformational stability. Employing the GIAO method, C-13 NMR chemical shifts of the C-2, C-2', C-4 and C-5 atoms were calculated at the same level of theory in the gas phase and with inclusion of solvent, and compared with experimental data. Push-pull effect of all compounds was quantified by means of the quotient pi*/pi, length of the partial double bond, C-13 NMR chemical shift difference (Delta delta(C=C)) and H-1 NMR chemical shifts of olefinic protons. The effect of bromine on donating and accepting ability of other substituents of the push- pull C=C double bond is discussed, too.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2010.09.040
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Ayi, Ayi A.
A1  - Khare, Varsha
A1  - Strauch, Peter
A1  - Girard, Jèrôme
A1  - Fromm, Katharina M.
A1  - Taubert, Andreas
T1  - On the chemical synthesis of titanium nanoparticles from ionic liquids
N2  - We report on attempts towards the synthesis of titanium nanoparticles using a wet chemical approach in imidazolium-based ionic liquids (ILs) under reducing conditions. Transmission electron microscopy finds nanoparticles in all cases. UV/Vis spectroscopy confirms the nanoparticulate nature of the precipitate, as in all cases an absorption band between ca. 280 and 300 nm is visible. IR spectroscopy shows that even after extensive washing and drying, some IL remains adsorbed on the nanoparticles. Raman spectroscopy suggests the formation of anatase nanoparticles, but X-ray diffraction reveals that, possibly, amorphous titania forms or that the nanoparticles are so small that a clear structure assignment is not possible. The report thus shows that (possibly amorphous) titanium oxides even form under reducing conditions and that the chemical synthesis of titanium nanoparticles in ILs remains elusive.
Y1  - 2010
UR  - http://www.springerlink.com/content/101572
U6  - https://doi.org/10.1007/s00706-010-0403-4
SN  - 0026-9247
ER  - 
TY  - JOUR
A1  - Awad, Duha Jawad
A1  - Conrad, Franziska
A1  - Koch, Andreas
A1  - Schilde, Uwe
A1  - Poeppl, Andreas
A1  - Strauch, Peter
T1  - 1,10-phenanthroline-dithiolate mixed ligand transition metal complexes : synthesis, characterization and EPR spectroscopy
N2  - A series of new N2S2 mixed ligand transition metal complexes, where N-2 is phenanthroline and S-2 is 1,2- dithiooxalate (dto) or 1,2-dithiosquarate (dtsq), has been synthesized and characterized. IR spectra reveal that the 1,2- dithiolate ligands are coordinated via the sulfur atoms forming a N2S2 coordination sphere. The copper(II) complex [Cu(phen)(dto)] was studied by EPR spectroscopy as a diamagnetically diluted powder. The diamagnetic dilution resulted from doping of the copper complex into the isostructural host lattice of the nickel complex [Ni(phen)(dto)]. The electronic situation in the frontier orbitals of the copper complex calculated from the experimental data is compared to the results of EHT and DFT calculations. Furthermore, one side product, chlorobis(1,10-phenanthroline)copper(I) ethanol solvate hydrate [(phen)(2)CuCl]center dot C2H5OH center dot H2O, was formed by a reduction process and characterized by X-ray diffraction. In the crystal packing one-dimensional columns of dimers are formed, stabilized by significant pi-pi interactions.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00201693
U6  - https://doi.org/10.1016/j.ica.2010.01.021
SN  - 0020-1693
ER  - 
TY  - JOUR
A1  - Awad, Duha Jawad
A1  - Conrad, Franziska
A1  - Koch, Andreas
A1  - Friedrich, Alwin
A1  - Poeppl, Andreas
A1  - Strauch, Peter
T1  - 2,2'-Bipyridin-1,2-dithiolat Gemischtligand-Komplexe : Systhese, Charakterisierung und EPR-Spektroskopie
N2  - A series of new 2 2'-bipyridine/1 2-dithiolate transition metal complexes has been synthesised and characterised As 1,2-dithiolate ligands 1,2 dithiooxalate (dto) and 1 2-dithiosquarate (dtsq) were used It follows from the IR spectra that the multidentate dithiolate ligands coordinate exclusively via their sulfur atoms forming an MN2S2 coordination sphere The central metal ions (M) are Cu2+ Ni2+ Pd2+ Pt2+, and Zn2+ The complex [Cu-II(bpy)(dto)] could be studied by EPR spectroscopy and was measured as powder diamagnetically diluted in the isostructural [Ni-II(bpy)(dto)] host structure The spin density contribution calculated from the experimental parameters is compared with the electronic situation in the frontier orbitals namely in the semi occupied SOMO of the copper complex derived from quantum chemical calculations on different levels (EHT and DFT)
Y1  - 2010
UR  - http://www.znaturforsch.com/b.htm
SN  - 0932-0776
ER  - 
TY  - JOUR
A1  - Adelsberger, Joseph
A1  - Kulkarni, Amit
A1  - Jain, Abhinav
A1  - Wang, Weinan
A1  - Bivigou Koumba, Achille Mayelle
A1  - Busch, Peter
A1  - Pipich, Vitaliy
A1  - Holderer, Olaf
A1  - Hellweg, Thomas
A1  - Laschewsky, André
A1  - Müller-Buschbaum, Peter
A1  - Papadakis, Christine M.
T1  - Thermoresponsive PS-b-PNIPAM-b-PS micelles : aggregation behavior, segmental dynamics, and thermal response
N2  - We have studied I lie thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylarnicle) (PNIPAM) middle block exhibiting a lower critical solution temperature (LCST) in aqueous solution. A wide range of concentrations (0.1-300 mg/mL) is investigated using it number of analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and neutron spin-echo spectroscopy (NSE). The critical micelle concentration is determined using FCS to be 1 mu M or less. The collapse of the micelles at the LCST is investigated using turbidimetry and DLS and shows a weak dependence on the degree of polymerization of the PNIPAM block. SANS with contrast matching allows its to reveal the core-shell Structure of the micelles as well as their correlation as a function of temperature. The segmental dynamics of the PNIPAM shell are studied as a function of temperature and arc found to be faster in the collapsed state than in the swollen state. The mode detected has a linear dispersion in q(2) and is found to be faster in the collapsed state as compared to the swollen state. We attribute this result to the averaging over mobile and immobilized segments.
Y1  - 2010
UR  - http://pubs.acs.org/journal/mamobx
U6  - https://doi.org/10.1021/Ma902714p
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Möllnitz, Kristian
A1  - Hübner, Sebastian
T1  - A short and efficient route from myo- to neo-inositol
N2  - An efficient route from myo- to neo-inositol is described. The key steps of the sequence are oxidation of the hydroxy group at C-5 to the corresponding ketone, followed by a highly (dr = 7.8:1) stereoselective reduction. The route includes nine steps with an overall yield of 51% and is therefore superior to all hitherto reported methods for the preparation of neo-inositol.
Y1  - 2010
UR  - http://www.thieme-connect.com/ejournals/toc/synlett
U6  - https://doi.org/10.1055/s-0029-1220071
SN  - 0936-5214
ER  - 
TY  - JOUR
A1  - Webster, Dean C.
A1  - Meier, Michael A. R.
T1  - Polymer libraries : preparation and applications
N2  - Polymer libraries offer straightforward opportunities for the investigation of structure property relationships and for a more thorough understanding of certain research problems. Furthermore, if combined with high-throughput methods for their preparation as well as screening, they offer the additional advantage of time savings and/or the reduction of experimental efforts. Thus, the herein discussed methods of polymer library preparation and selected literature examples of polymer libraries describe efficient and state-of-the-art methods to tackle difficult research challenges in polymer and materials science.
Y1  - 2010
UR  - http://www.springerlink.com/content/tk40663747722833/
U6  - https://doi.org/10.1007/12_2009_15
SN  - 0065-3195
ER  - 
TY  - JOUR
A1  - Wang, Weijia
A1  - Kaune, Gunar
A1  - Perlich, Jan
A1  - Paradakis, Christine M.
A1  - Bivigou Koumba, Achille Mayelle
A1  - Laschewsky, André
A1  - Schlage, K.
A1  - Röhlsberger, Ralf
A1  - Roth, Stephan V.
A1  - Cubitt, Robert
A1  - Müller-Buschbaum, Peter
T1  - Swelling and switching kinetics of gold coated end-capped poly(N-isopropylacrylamide) thin films
N2  - Thin thermoresponsive hydrogel films of poly(N-isopropylacrylamide) end-capped with n-butyltrithiocarbonate(nbc- PNIPAM) oil si I icon supports with a gold layer on top, causing an asymmetric confinement, are investigated. For two different gold layer thicknesses (nominally 0.4 and 5 rim), the swelling and switching kinetics are probed with in situ neutron reflectivity. With a temperature jump from 23 to 40 degrees C the film is switched from a swollen into a collapsed state. For the thin gold layer this switching is faster as compared to the thick gold layer. The switching is a two-step process of water release and a subsequent structural relaxation. fit swelling and deswelling cycles, aging of the films is probed. After five cycles, the film exhibits enhanced water storage capacity. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that these gold coated nbc-PNIPAM films do not age with respect to the inner structure but slightly roughen at the gold surface. As revealed by atomic force microscopy, the morphology of the gold layer is changed by the water uptake and release.
Y1  - 2010
UR  - http://pubs.acs.org/journal/mamobx
U6  - https://doi.org/10.1021/Ma902637a
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Vukicevic, Radovan
A1  - Hierzenberger, Peter
A1  - Hild, Sabine
A1  - Beuermann, Sabine
T1  - Functionalization of carbon black nanoparticles with poly(vinylidene fluoride)
N2  - The surface of carbon black (CB) nanoparticles was functionalized with poly(vinylidene fluoride) (PVDF) either by trapping of macroradicals or by cycloaddition. PVDF with two iodine end groups (I-PVDF-I) obtained from iodine transfer polymerization in supercritical CO2 was heated in the presence of CB and the C-I bond was cleaved resulting in a reaction between the macroradical and the CB surface. To allow for cycloaddition of PVDF to the CB surface for a number of polymers, the iodine end groups were replaced by azide end groups. In addition, microwave irradiation was applied to the functionalization. The influence of temperature, time, polymer concentration, and polymer molar mass on the functionalization reaction was examined.
Y1  - 2010
UR  - http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291542-9369
U6  - https://doi.org/10.1002/Pola.24277
SN  - 0887-624X
ER  - 
TY  - JOUR
A1  - Uhlig, Katja
A1  - Wischerhoff, Erik
A1  - Lutz, Jean-Francois
A1  - Laschewsky, André
A1  - Jäger, Magnus S.
A1  - Lankenau, Andreas
A1  - Duschl, Claus
T1  - Monitoring cell detachment on PEG-based thermoresponsive surfaces using TIRF microscopy
N2  - Recently, we introduced a thermoresponsive copolymer that consists of oligo(ethylene glycol) methacrylate (OEGMA) and 2-(2- methoxyethoxy) ethyl methacrylate (MEO(2)MA). The polymer exhibited an LCST at 35 degrees C in PBS buffer and was anchored onto gold substrates using disulfide polymerisation initiators. It allows the noninvasive detachment of adherent cells from their substrate. As the mechanisms that determine the interaction of cells with such polymers are not well understood, we employed Total Internal Reflection Fluorescence (TIRF) microscopy in order to monitor the detachment process of cells of two different types. We identified contact area and average cell-substrate distance as crucial parameters for the evaluation of the detachment process. The sensitivity of TIRF microscopy allowed us to correlate the specific adhesion pattern of MCF-7 breast cancer cells with the morphology of cell deposits that may serve as fingerprints for a nondestructive characterisation of live cells.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/sm/index.asp
U6  - https://doi.org/10.1039/C0sm00010h
SN  - 1744-683X
ER  - 
TY  - JOUR
A1  - Türünc, Oguz
A1  - Meier, Michael A. R.
T1  - Fatty acid derived monomers and related polymers via Thiol-ene (click) additions
N2  - Thiol-ene additions of methyl 10-undecenoate, a castor oil derived renewable platform chemical, were studied with the goal of preparing a set of renewable monomers. Good to excellent yields were obtained for these solvent and initiator free thiol-ene additions. The resulting monomers were then polymerized using TBD as a catalyst, to linear as well as hyperbranched polyesters that also contain thio-ether linkages. All thus prepared polymers were fully characterized (NMR, GPC, DSC, and TGA) and the results of these investigations will be discussed within this contribution. The thermal analysis of these polymers revealed melting points in the range from 50 to 71 degrees C. Moreover, no significant weight loss was observed below 300 degrees C.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/10003270
U6  - https://doi.org/10.1002/marc.201000291
SN  - 1022-1336
ER  - 
TY  - JOUR
A1  - Tronci, Giuseppe
A1  - Neffe, Axel T.
A1  - Pierce, Benjamin Franklin
A1  - Lendlein, Andreas
T1  - An entropy-elastic gelatin-based hydrogel system
N2  - Gelatin is a non-immunogenic and degradable biopolymer, which is widely applied in the biomedical field e. g. for drug capsules or as absorbable hemostats. However, gelatin materials present limited and hardly reproducible mechanical properties especially in aqueous systems, particularly caused by the uncontrollable partial renaturation of collagen-like triple helices. Therefore, mechanically demanding applications for gelatin-based materials, such as vascular patches, i.e. hydrogel films that seal large incisions in vessel walls, and for induced autoregeneration, are basically excluded if this challenge is not addressed. Through the synthesis of a defined chemical network of gelatin with hexamethylene diisocyanate (HDI) in DMSO, the self-organization of gelatin chains could be hindered and amorphous gelatin films were successfully prepared having Young's moduli of 60-530 kPa. Transferring the crosslinking reaction with HDI and, alternatively, ethyl lysine diisocyanate (LDI), to water as reaction medium allowed the tailoring of swelling behaviour and mechanical properties by variation of crosslinker content while suppressing the formation of helices. The hydrogels had Young's moduli of 70-740 kPa, compressive moduli of 16-48 kPa, and degrees of swelling of 300-800 vol%. Test reactions investigated by ESI mass spectrometry allowed the identification and quantification of reaction products of the crosslinking reaction. The HDI crosslinked networks were stabilized by direct covalent crosslinks (ca. 10 mol%), supported by grafting (50 mol%) and blending of hydrophobic oligomeric chains. For the LDI- based networks, less crosslinked (3 mol%) and grafted species (5 mol%) and much higher amounts of oligomers were observed. The adjustable hydrogel system enables the application of gelatin-based materials in physiological environments.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/jm/index.asp
U6  - https://doi.org/10.1039/C0jm00883d
SN  - 0959-9428
ER  - 
TY  - JOUR
A1  - Tremblay, Jean Christophe
A1  - Krause, Pascal
A1  - Klamroth, Tillmann
A1  - Saalfrank, Peter
T1  - Time-dependent response of dissipative electron systems
N2  - We present a systematic study of the influence of energy and phase relaxation on dynamic polarizability simulations in the linear response regime. The nonperturbative approach is based on explicit electron dynamics using short laser pulses of low intensities. To include environmental effects on the property calculation, we use the time- dependent configuration-interaction method in its reduced density matrix formulation. Both energy dissipation and nonlocal pure dephasing are included. The explicit treatment of time-resolved electron dynamics gives access to the phase shift between the electric field and the induced dipole moment, which can be used to define a useful uncertainty measure for the dynamic polarizability. The nonperturbative treatment is compared to perturbation theory expressions, as applied to a simple model system, the rigid H-2 molecule. It is shown that both approaches are equivalent for low field intensities, but the time-dependent treatment provides complementary information on the phase of the induced dipole moment, which allows for the definition of an uncertainty associated with the computation of the dynamic polarizability in the linear response regime.
Y1  - 2010
UR  - http://pra.aps.org/
U6  - https://doi.org/10.1103/Physreva.81.063420
SN  - 1050-2947
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Parvulescu, Vasile Ion
A1  - Cojocaru, Bogdan
A1  - Lorenz-Fonfria, Victor A.
A1  - Kumke, Michael Uwe
A1  - Gessner, Andre
A1  - Enculescu, Ion
T1  - Polymer-microporous host interactions probed by photoluminescence spectroscopy
N2  - Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/CP/index.asp
U6  - https://doi.org/10.1039/B922591a
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Parvulescu, Vasile
A1  - Parvulescu, Victoria
A1  - Cotoi, Elena
A1  - Gessner, Andre
A1  - Kumke, Michael Uwe
A1  - Simon, Simion
A1  - Vasiliu, Florin
T1  - Structural and photoluminescence characterization of mesoporous silicon-phosphates
N2  - Two different types of mesoporous silicon-phosphate supports using different surfactants (a mixture of (CH3)(3)C13H27NBr with an organophosphorus coupling molecule (HO-PO(i-C3H7)(2)) and with a co-surfactant ((C2H5)(3)(C6H5)PCl), respectively) were synthesized. Trivalent europium (Eu) ions were immobilized via ion-exchange on these supports. The resulting materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, SEM, TEM, FT-IR, PXRD, CP/MAS. (HSi)-H-1-Si-29 and P-31 NMR, DR-UV-vis as well as steady- state and time-resolved photoluminescence spectroscopy. The results evidenced that the co-polymerization of silicon and phosphorous yielded a unique morphology in these materials. Following calcination at 450 and 900 degrees C europium- exchanged silicon-phosphates with great surface area (BET=600-705 m(2) g(-1)) and 3.4 nm sized mesopores were obtained. The differences among the optical properties of the non-calcined europium materials such as the emission lifetimes, local environment at the europium sites or the relative contribution of the upper excited levels to the total photoluminescence were assigned to the surfactants used in the synthesis. Calcination of the silicon-phosphates at higher temperatures than 450 degrees C did not induce major changes in the structural properties: in contrast, photoluminescence properties of europium were markedly improved in terms of intensity and average lifetime.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/10106030
U6  - https://doi.org/10.1016/j.jphotochem.2010.07.015
SN  - 1010-6030
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Rexhausen, Hans
A1  - Strauch, Peter
A1  - Strehmer, Bernd
T1  - Temperature dependence of interactions between stable piperidine-1-yloxyl derivatives and a semicrystalline ionic liquid
N2  - The stable 2,2,6,6-tetramethylpiperidine-1-yloxyl and its derivatives with hydrogen-bond-forming (-OH, -OSO3H), anionic (-OSO3- bearing K+ or [K(18-crown-6)](+) as counter ion), or cationic (-N+-(CH3)(3) bearing I-, BF4-, PF6- or N- (SO2CF3)(2) as counter ion) substituents are investigated in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide over a wide temperature range. The temperature dependence of the viscosity of the ionic liquid is well described by the Vogel-Fulcher-Tammann equation. Interestingly, the temperature dependence of the rotational correlation time of the spin probes substituted with either a hydrogen-bond-forming group or an ionic substituent can be described using the Stokes-Einstein equation. In contrast, the temperature dependence of the rotational correlation time of the spin probe without an additional substituent at the 4-position to the nitroxyl group does not follow this trend. The activation energy for the mobility of the unsubstituted spin probe, determined from an Arrhenius plot of the spin-probe mobility in the ionic liquid above the melting temperature, is comparable with the activation energy for the viscous flow of the ionic liquid, but is higher for spin probes bearing an additional substituent at the 4-position. Quantum chemical calculations of the spin probes using the 6-31G+d method give information about the rotational volume of the spin probes and the spin density at the nitrogen atom of the radical structure as a function of the substituent at the spin probes in the presence and absence of a counter ion. The results of these calculations help in understanding the effect of the additional substituent on the experimentally determined isotropic hyperfine coupling constant.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/72514732/
U6  - https://doi.org/10.1002/cphc.200900977
SN  - 1439-4235
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Rexhausen, Hans
A1  - Strauch, Peter
T1  - Influence of imidazolium bis(trifluoromethylsulfonylimide)s on the rotation of spin probes comprising ionic and hydrogen bonding groups
N2  - The influence of the alkyl chain length in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonylimide)s is studied to explore the rotation of piperidine-1-yloxyl derivatives substituted with either hydrogen bonding hydroxy group or ionic substituents, such as the cationic trimethylammonium or the anionic sulfate group placed at the 4 position. Structural variation of the ionic liquids results in differences of their viscosity influencing the rotation of the spin probes. The size of the average rotational correlation times of the spin probes dissolved in the ionic liquids depends further on the additional substituent in 4-position at these spin probes. The rotational correlation time exhibits a linear dependence on the ionic liquid viscosity in the case of the spin probe forming hydrogen bonding with the ionic liquids. In contrast to this, a deviation from the Stokes-Einstein behavior is found in the case of rotation of the charged spin probes in the 1-alkyl-3-methylimidazolium bis( trifluoromethylsulfonylimide) s substituted with a longer alkyl chain. This effect may be explained by phase separation on a molecular level between the charged part of the ionic liquid and the longer alkyl chains bound at the imidazolium ion. Although the neutral and the cationic spin probes show only a slight dependence between ionic liquid structure variation and the hyperfine coupling constants, structural effects cause changes in the hyperfine coupling constants in the case of the anionic spin probes. These probes strongly interact with the imidazolium ion.
Y1  - 2010
UR  - http://www.rsc.org/Publishing/Journals/CP/index.asp
U6  - https://doi.org/10.1039/B920586a
SN  - 1463-9076
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Rexhausen, Hans
A1  - Strauch, Peter
T1  - 2,2,6,6-Tetramethylpiperidine-1-yloxyl bound to the imidazolium ion by an acetamido group for investigation of ionic liquids
N2  - New spin probes bearing the 2,2,6,6-tetramethylpiperidine-1-yloxyl covalently bound to the imidazolium ion via a methylene spacer and an amide group are synthesized. If the anion is bis(trifluoromethylsulfonylimide) instead of iodide, the new spin probe has a similar structure as that of an ionic liquid. Nevertheless, the new spin probes are useful tools to investigate ionic liquids.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00404039
U6  - https://doi.org/10.1016/j.tetlet.2009.11.124
SN  - 0040-4039
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Lungwitz, Ralf
A1  - Rexhausen, Hans
A1  - Spange, Stefan
T1  - Relationship between hyperfine coupling constants of spin probes and empirical polarity parameters of some ionic liquids
N2  - The polarity of 1-alkyl-3-methylimidazolium-based ionic liquids containing hexafluorophosphate, tetrafluoroborate, dicyanoimide, or bis(trifluoromethanesulfonyl) imide as anions and a variation of the alkyl-chain length of the cation are investigated by both solvatochromic dyes and spin probes. Two different polarity scales are used for discussion of the polarity of these ionic liquids. These polarity scales are the empirical Kamlet-Taft parameters alpha, beta, and pi* and the hyperfine coupling constants A(iso)(N-14) obtained for spin probes substituted either with an ammonio or a sulfate group at 4-position. The results show that both polarity scales are valid for description of the ionic liquid polarity although differences are found between the two polarity scales. The most clear trend is found in all ionic liquids investigated for the hydrogen-bond accepting ability (beta) and the hyperfine- coupling constant of the anionic spin probe, where both parameters increase for all ionic liquids investigated until an alkyl chain length of eight carbon atoms and keep constant at longer alkyl chains.
Y1  - 2010
UR  - http://rsc.org/Publishing/Journals/nj/
U6  - https://doi.org/10.1039/C0nj00253d
SN  - 1144-0546
ER  -