TY - JOUR A1 - Garnier, Sebastien A1 - Laschewsky, Andre T1 - Non-ionic amphiphilic block copolymers by RAFT-polymerization and their self-organization JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - Water-soluble, amphiphilic diblock copolymers were synthesized by reversible addition fragmentation chain transfer polymerization. They consist of poly(butyl acrylate) as hydrophobic block with a low glass transition temperature and three different nonionic water-soluble blocks, namely, the classical hydrophilic block poly(dimethylacrylamide), the strongly hydrophilic poly(acryloyloxyethyl methylsulfoxide), and the thermally sensitive poly(N-acryloylpyrrolidine). Aqueous micellar solutions of the block copolymers were prepared and characterized by static and dynamic light scattering analysis (DLS and SLS). No critical micelle concentration could be detected. The micellization was thermodynamically favored, although kinetically slow, exhibiting a marked dependence on the preparation conditions. The polymers formed micelles with a hydrodynamic diameter from 20 to 100 nm, which were stable upon dilution. The micellar size was correlated with the composition of the block copolymers and their overall molar mass. The micelles formed with the two most hydrophilic blocks were particularly stable upon temperature cycles, whereas the thermally sensitive poly(N-acryloylpyrrolidine) block showed a temperature-induced precipitation. According to combined SLS and DLS analysis, the micelles exhibited an elongated shape such as rods or worms. It should be noted that the block copolymers with the most hydrophilic poly(sulfoxide) block formed inverse micelles in certain organic solvents. KW - macrosurfactants KW - block copolymers KW - micelles KW - inverse micelles KW - sulfoxide Y1 - 2006 U6 - https://doi.org/10.1007/s00396-006-1484-9 SN - 0303-402X VL - 284 SP - 1243 EP - 1254 PB - Springer CY - Berlin ER - TY - JOUR A1 - Füchsel, Gernot A1 - Klamroth, Tillmann A1 - Dokic, Jadranka A1 - Saalfrank, Peter T1 - On the electronic structure of neutral and ionic azobenzenes and their possible role as surface mounted molecular switches JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - We report quantum chemical calculations, mostly based on density functional theory, on azobenzene and substituted azobenzenes as neutral molecules or ions, in ground and excited states. Both the cis and trans configurations are computed as well as the activation energies to transform one isomer into the other and the possible reaction paths and reaction surfaces along the torsion and inversion modes. All calculations are done for the isolated species, but results are discussed in light of recent experiments aiming at the switching of surface mounted azobenzenes by scanning tunneling microscopes. Y1 - 2006 U6 - https://doi.org/10.1021/jp060969v SN - 1520-6106 VL - 110 IS - 33 SP - 16337 EP - 16345 PB - Soc. CY - Washington ER - TY - GEN A1 - Lutz, Jean-Francois A1 - Kristen, Juliane A1 - Skrabania, Katja A1 - Laschewsky, Andre T1 - POLY 14-Synthetic strategies for preparing multicompartment micelles T2 - Abstracts of papers / American Chemical Society N2 - The fabrication of compartmented micellar systems is an exciting new area of research in the field of polymer self-assembly. Multicompartment micelles composed of a water-soluble shell and a segregated hydrophobic core can be obtained via direct aqueous self-assembly of preformed polymeric amphiphiles possessing one hydrophilic segment and two incompatible hydrophobic segments (e.g. hydrocarbon and fluorocarbon blocks). Such macromolecular building-blocks were prepared in the present work principally via reversible addition-fragmentation transfer polymerization (RAFT). Polysoaps or triblock macrosurfactants can be synthesized in high yields by RAFT under relatively straightforward experimental conditions. Y1 - 2006 SN - 0-8412-7426-6 SN - 0065-7727 VL - 232 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Nave, Stefan T1 - Stereoselective syntheses of enantiomerically pure 2,5-disubstituted dihydropyrans based on olefin metathesis JF - The journal of organic chemistry N2 - A short synthesis of 2,5-disubstituted dihydropyrans starting from D-mannitol as a chiral building block is described. Our synthetic approach combines ruthenium-catalyzed ring closing olefin metathesis and palladium-catalyzed nucleophilic substitution. Y1 - 2006 U6 - https://doi.org/10.1021/jo061190k SN - 0022-3263 VL - 71 IS - 19 SP - 7364 EP - 7369 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kapp, A. A1 - Beissenhirtz, Moritz Karl A1 - Geyer, F. A1 - Scheller, F. A1 - Viezzoli, Maria Silvia A1 - Lisdat, Fred T1 - Electrochemical and sensorial behavior of SOD mutants immobilized on gold electrodes in aqueous/organic solvent mixtures JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - A cysteine mutant of a monomeric human Cu, Zn-SOD (Glycine 61, Serine 142) has been immobilized directly on gold electrodes using the thiol groups introduced. The electrochemical behavior of the surface confined protein was studied in mixtures of aqueous buffer and DMSO up to an organic solvent content of 60%. The formal potential was found to be rather independent of the DMSO content. However, half peak width increased and the redoxactive amount clearly decreased with raising DMSO content. In addition, the kinetics of the heterogeneous electron transfer became slower; but still a quasireversible electrochemical conversion of the mutant SOD was feasible. Thus, the electrodes were applied for sensorial superoxide detection. At a potential of +220 mV vs. Ag/AgCl advantage was taken of the partial oxidation reaction of the enzyme. A defined superoxide signal was obtained in solutions up to 40% DMSO. The sensitivity of the mutant electrodes decreased linearly with the organic solvent content in solution but was still higher compared to conventional cyt.c based sensors. At DMSO concentrations higher than 40% no sensor response was detected. KW - SOD KW - mutants KW - gold electrodes KW - DMSO KW - electrochemistry Y1 - 2006 U6 - https://doi.org/10.1002/elan.200603620 SN - 1040-0397 VL - 18 SP - 1909 EP - 1915 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Saalfrank, Peter T1 - Quantum dynamical approach to ultrafast molecular desorption from surfaces JF - Chemical reviews Y1 - 2006 U6 - https://doi.org/10.1021/cr0501691 SN - 0009-2665 SN - 1520-6890 VL - 106 IS - 10 SP - 4116 EP - 4159 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Note, Carine A1 - Koetz, Joachim A1 - Kosmella, Sabine T1 - Structural changes in poly(ethyleneimine) modified microemulsion JF - Journal of colloid and interface science N2 - The influence of branched poly(ethyleneimine) on the phase behavior of the system sodium dodecylsulfate/toluene-pentanol (1:1)/water has been studied. The isotropic microemulsions still exist when water is replaced with aqueous solutions of PEI (up to 30% in weight), but their stability is significantly influenced. From a polymer concentration of 20 wt%, the polymer enhances the solubilization of water in oil, changes the sign of the spontaneous curvature of the surfactant film, and induces an inversion of the microemulsion type from water-in-oil (L-2) to oil-in-water (L-1), by the formation of a bicontinuous channel. Further investigations show that the addition of polymer in the L-2 phase changes the droplet-droplet interactions as the conductivity drops and the percolation disappears. In the bicontinuous channel, higher viscosities can be detected, as well as a weak percolation followed by a steep increase of the conductivity, which can be related to evident structural changes in the system. DSC measurements allow then to follow the changes of the water properties in the system, from interfacial-water in the L-2 phase to free-water in the sponge-like phase. Finally, all the measurements performed permit to characterize the structural transitions in the system and to understand the role of the added polymer. KW - polyelectrolyte KW - microemulsion KW - bicontinuous phase Y1 - 2006 U6 - https://doi.org/10.1016/j.jcis.2006.06.071 SN - 0021-9797 VL - 302 SP - 662 EP - 668 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Lange, Birger A1 - Wagner, Jürgen A1 - Zentel, Rudolf T1 - Fabrication of robust high-quality ORMOCER (R) inverse opals JF - Macromolecular rapid communications N2 - The nanostructuring of ORMOCER (R) to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER (R). After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER (R) inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER (R) and high temperature stability up to 350 degrees C. KW - colloids KW - inverse opals KW - ORMOCER (R) KW - photonic crystal KW - self-assembly Y1 - 2006 U6 - https://doi.org/10.1002/marc.200600429 SN - 1022-1336 VL - 27 SP - 1746 EP - 1751 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Teixeira, C. V. A1 - Blanzat, Muriel A1 - Koetz, Joachim A1 - Rico-Lattes, I. A1 - Brezesinski, Gerald T1 - In-plane miscibility and mixed bilayer microstructure in mixtures of catanionic glycolipids and zwitterionic phospholipids JF - Biochimica et biophysica acta : Biomembranes N2 - SAXS/WAXS studies were performed in combination with freeze fracture electron microscopy using mixtures of a new Gemini catanionic surfactant (Gem 16-12, formed by two sugar groups bound by a hydrocarbon spacer with 12 carbons and two 16-carbon chains) and the zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC) to establish the phase diagram. Gem 16-12 in water forms bilayers with the same amount of hydration water as DPPC. A frozen interdigitated phase with a low hydration number is observed below room temperature. The kinetics of the formation of this crystalline phase is very slow. Above the chain melting temperature, multilayered vesicles are formed. Mixing with DPPC produces mixed bilayers above the corresponding chain melting temperature. At room temperature, partially lamellar aggregates with local nematic order are observed. Splitting of infinite lamellae into discs is linked to immiscibility in frozen state. The ordering process is always accompanied by dehydration of the system. As a consequence, an unusual order-disorder phase transition upon cooling is observed. KW - SAXS KW - bilayer KW - gemini surfactant KW - ordering process KW - Anti-HIV KW - miscibility Y1 - 2006 U6 - https://doi.org/10.1016/j.bbamem.2006.05.025 SN - 0005-2736 VL - 1758 SP - 1797 EP - 1808 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kozlevcar, Bojan A1 - Golobic, Amalija A1 - Strauch, Peter T1 - Dynamic pseudo Jahn-Teller distortion in a compressed octahedral CuO6 complex JF - Polyhedron : the international journal of inorganic and organometallic chemistry N2 - The crystal structure of cis-[Cu(C8H7O3)(2)(H2O)(2)] (115 K data) reveals bidentate vanillinate ions coordinated via methoxy and deprotonated hydroxy oxygen atoms and water molecules in a distorted octahedral CuO6 chromophore. A cis orientation of the ligands enables two non-identical O(methoxy)-Cu-O(water) coordination axes (2.354(l) + 2.163(1); 2.151(1) + 2.020(1) angstrom), and the third shortest O(hydroxy)-Cu-O(hydroxy) axis (1.919(1) + 1.914(1) angstrom). This 115 K coordination sphere differs importantly to the one obtained from the 293 K data of the same compound, where two long 0(methoxy)-Cu-O(water) axes are of the same length, and only minor changes at the short 0(hydroxy)-Cu-O(hydroxy) axis are noticed. An axial symmetry of the complex with an inverse g(1.2)(g(perpendicular to)) > g(3)(g(parallel to)) pattern is observed in the temperature range from 298 to 180 K. A further decrease of temperature reveals gradual changes from axial to rhombic symmetry (g(1) > g(2) > g(3)) that is reversible. A mean-square displacement amplitude (MDSA) analysis reveals a disorder in the Cu-O(methoxy) bonds, but not in the other metal-ligand Cu-O(hydroxy) and Cu-O(water) bonds at 293 and 115 K. The disorder is significantly weaker in the 115 K structure. The MSDA analysis and the structural-EPR agreement show vibrational disorder in two coordination axes, due to the cis conformation of the complex with two 0(methoxy)-Cu-O(water) axes. KW - copper KW - vanillin KW - Jahn-Teller distortion KW - MSDA KW - cis KW - EPR Y1 - 2006 U6 - https://doi.org/10.1016/j.poly.2006.04.009 SN - 0277-5387 VL - 25 IS - 15 SP - 2824 EP - 2828 PB - Elsevier CY - Oxford ER -