TY - JOUR A1 - Zehm, Daniel A1 - Laschewsky, André A1 - Liang, Hua A1 - Rabe, Jürgen P. T1 - Straightforward access to amphiphilic dual bottle brushes by combining RAFT, ATRP, and NMP polymerization in one sequence JF - Macromolecules : a publication of the American Chemical Society N2 - Molecular brush diblock copolymers were synthesized by the orthogonal overlay of the RAFT (reversible addition-fragmentation chain transfer), the ATRP (atom transfer radical polymerization), and the NMP (nitroxide-mediated polymerization) techniques. This unique combination enabled the synthesis of the complex amphiphilic polymers without the need of postpolymerization modifications, using a diblock copolymer intermediate made from two selectively addressable inimers and applying a sequence of four controlled free radical polymerization steps in total. The resulting polymers are composed of a thermosensitive poly(N-isopropylacrylamide) brush as hydrophilic block and a polystyrene brush as hydrophobic block, thus translating the structure of the established amphiphilic diblock copolymers known as macro surfactants to the higher size level of "giant surfactants". The dual molecular brushes and the aggregates formed on ultra flat solid substrates were visualized by scanning force microscopy (SFM). Y1 - 2011 U6 - https://doi.org/10.1021/ma2015613 SN - 0024-9297 VL - 44 IS - 24 SP - 9635 EP - 9641 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zehm, Daniel A1 - Laschewsky, André A1 - Heunemann, Peggy A1 - Gradzielski, Michael A1 - Prevost, Sylvain A1 - Liang, Hua A1 - Rabe, Jürgen P. A1 - Lutz, Jean-Francois T1 - Synthesis and self-assembly of amphiphilic semi-brush and dual brush block copolymers in solution and on surfaces JF - Polymer Chemistry N2 - The combination of two techniques of controlled free radical polymerization, namely the reversible addition fragmentation chain transfer (RAFT) and the atom transfer radical polymerization (ATRP) techniques, together with the use of a macromonomer allowed the synthesis of symmetrical triblock copolymers, designed as amphiphilic dual brushes. One type of brush was made of poly(n-butyl acrylate) as soft hydrophobic block, i.e. characterized by a low glass transition temperature, while the other one was made of hydrophilic poly(ethylene glycol) (PEG). The new triblock polymers represent "giant surfactants" according to their molecular architecture. The hydrophobic and hydrophilic blocks microphase separate in the bulk. In aqueous solution, they aggregate into globular micellar aggregates, their size being determined by the length of the stretched polymer molecules. As determined by the combination of various scattering techniques for the dual brush copolymer, a rather compact structure is formed, which is dominated by the large hydrophobic poly(n-butyl acrylate) block. The aggregation number for the dual brush is about 10 times larger than for the "semi-brush" precursor copolymer, due to the packing requirements for the much bulkier hydrophobic core. On mica surfaces the triblock copolymers adsorb with worm-like backbones and stretched out side chains. Y1 - 2011 U6 - https://doi.org/10.1039/c0py00200c SN - 1759-9954 VL - 2 IS - 1 SP - 137 EP - 147 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zaupa, Alessandro A1 - Neffe, Axel T. A1 - Pierce, Benjamin F. A1 - Lendlein, Andreas A1 - Hofmann, Dieter T1 - A molecular dynamic analysis of gelatin as an amorphous material Prediction of mechanical properties of gelatin systems JF - The international journal of artificial organs N2 - Biomaterials are used in regenerative medicine for induced autoregeneration and tissue engineering. This is often challenging, however, due to difficulties in tailoring and controlling the respective material properties. Since functionalization is expected to offer better control, in this study gelatin chains were modified with physically interacting groups based on tyrosine with the aim of causing the formation of physical crosslinks. This method permits application-specific properties like swelling and better tailoring of mechanical properties. The design of the crosslink strategy was supported by molecular dynamic (MD) simulations of amorphous bulk models for gelatin and functionalized gelatins at different water contents (0.8 and 25 wt.-%). The results permitted predictions to be formulated about the expected crosslink density and its influence on equilibrium swelling behavior and on elastic material properties. The models of pure gelatin were used to validate the strategy by comparison between simulated and experimental data such as density, backbone conformation angle distribution, and X-ray scattering spectra. A key result of the simulations was the prediction that increasing the number of aromatic functions attached to the gelatin chain leads to an increase in the number of physical netpoints observed in the simulated bulk packing models. By comparison with the Flory-Rehner model, this suggested reduced equilibrium swelling of the functionalized materials in water, a prediction that was subsequently confirmed by our experimental work. The reduction and control of the equilibrium degree of swelling in water is a key criterion for the applicability of functionalized gelatins when used, for example, as matrices for induced autoregeneration of tissues. KW - Physical Network KW - Biopolymer material KW - Molecular modeling KW - Gelatin Y1 - 2011 U6 - https://doi.org/10.5301/IJAO.2010.6083 SN - 0391-3988 VL - 34 IS - 2 SP - 139 EP - 151 PB - Wichtig CY - Milano ER - TY - JOUR A1 - Yuan, Jiayin A1 - ten Brummelhuis, Niels A1 - Junginger, Mathias A1 - Xie, Zailai A1 - Lu, Yan A1 - Taubert, Andreas A1 - Schlaad, Helmut T1 - Diversified applications of chemically modified 1,2-Polybutadiene JF - Macromolecular rapid communications N2 - Commercially available 1,2-PB was transformed into a well-defined reactive intermediate by quantitative bromination. The brominated polymer was used as a polyfunctional macroinitiator for the cationic ring-opening polymerization of 2-ethyl-2-oxazoline to yield a water-soluble brush polymer. Nucleophilic substitution of bromide by 1-methyl imidazole resulted in the formation of polyelectrolyte copolymers consisting of mixed units of imidazolium, bromo, and double bond. These copolymers, which were soluble in water without forming aggregates, were used as stabilizers in the heterophase polymerization of styrene and were also studied for their ionic conducting properties. KW - emulsion polymerization KW - polybutadiene KW - polyelectrolytes KW - polymer modification KW - ring-opening polymerization Y1 - 2011 U6 - https://doi.org/10.1002/marc.201100254 SN - 1022-1336 VL - 32 IS - 15 SP - 1157 EP - 1162 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Yin, Jian A1 - Linker, Torsten T1 - Stereoselective diversity-oriented syntheses of functionalized saccharides from bicyclic carbohydrate 1,2-lactones JF - Tetrahedron N2 - Bicyclic carbohydrate 1,2-lactones have been synthesized in only two steps and high yields by saponification and subsequent cyclization from known malonate addition products to glycals. The gluco-configured lactone serves as an important precursor for diversity-oriented syntheses. Thus, stereoselective opening of the lactone ring was realized with various nucleophiles in the presence of Sc(OTf)(3). This enabled the introduction of different substituents at the anomeric position, to afford a broad variety of 1-functionalized carbohydrates. On the other hand, stereoselective alpha-substitution of the gluco-configured lactone with different electrophiles and subsequent ring opening gives a collection of 2-functionalized saccharides. More than 30 products have been isolated in analytically pure form, and their configurations were unequivocally established by various NMR methods. Thus, carbohydrate 1,2-lactones are attractive precursors for the stereoselective synthesis of diverse saccharides. KW - Carbohydrates KW - Lactones KW - Glycosides KW - Molecular diversity KW - Synthetic methods Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.01.069 SN - 0040-4020 VL - 67 IS - 13 SP - 2447 EP - 2461 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Yarman, Aysu A1 - Nagel, Thomas A1 - Gajovic-Eichelmann, Nenad A1 - Fischer, Anna A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Bioelectrocatalysis by Microperoxidase-11 in a Multilayer Architecture of Chitosan Embedded Gold Nanoparticles JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - We report on the redox behaviour of the microperoxidase-11 (MP-11) which has been electrostatically immobilized in a matrix of chitosan-embedded gold nanoparticles on the surface of a glassy carbon electrode. MP-11 contains a covalently bound heme c as the redox active group that exchanges electrons with the electrode via the gold nanoparticles. Electroactive surface concentration of MP-11 at high scan rate is between 350+/-50 pmol cm(-2), which reflects a multilayer process. The formal potential (E degrees') of MP-11 in the gold nanoparticles-chitosan film was estimated to be -(267.7+/-2.9) mV at pH 7.0. The heterogeneous electron transfer rate constant (k(s)) starts at 1.21 s(-1) and levels off at 6.45 s(-1) in the scan rate range from 0.1 to 2.0 V s(-1). Oxidation and reduction of MP-11 by hydrogen peroxide and superoxide, respectively have been coupled to the direct electron transfer of MP-11. KW - Microperoxidase KW - Direct electron transfer KW - Nanoparticles KW - Hydrogen peroxide KW - Superoxide KW - Bioelectrocatalysis Y1 - 2011 U6 - https://doi.org/10.1002/elan.201000535 SN - 1040-0397 VL - 23 IS - 3 SP - 611 EP - 618 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Xie, Zai-Lai A1 - White, Robin J. A1 - Weber, Jens A1 - Taubert, Andreas A1 - Titirici, Magdalena M. T1 - Hierarchical porous carbonaceous materials via ionothermal carbonization of carbohydrates JF - Journal of materials chemistry N2 - We report on the ionothermal synthesis of porous carbon materials from a variety of carbohydrate precursors (i.e. D-glucose, D-fructose, D-xylose, and starch) using 1-butyl-3-methylimidazolium tetrachloroferrate(III), [Bmim][FeCl(4)] as a reusable solvent and catalyst. The carbon materials derived from these different carbohydrates are similar in terms of particle size and chemical composition, possessing relatively high surface areas from 44 to 155 m(2) g(-1) after ionothermal processing, which can be significantly increased to > 350 m(2) g(-1) by further thermal treatment (e. g. post-carbonization at 750 degrees C). CO(2) and N(2) sorption analysis, combined with Hg intrusion porosimetry, reveals a promising hierarchical pore structuring to these carbon materials. The ionic liquid [Bmim][FeCl(4)] has a triple role: it acts as both a soft template to generate the characterized pore structuring, solvent and as a catalyst resulting in enhanced ionothermal carbon yields. Importantly from a process point of view, the ionic liquid can be successfully recovered and reused. The current work shows that ionothermal synthesis has the potential to be an effective, low cost, and green reusable synthetic route towards sustainable porous carbon materials. Y1 - 2011 U6 - https://doi.org/10.1039/c1jm00013f SN - 0959-9428 VL - 21 IS - 20 SP - 7434 EP - 7442 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Xie, Zai-Lai A1 - Taubert, Andreas T1 - Thermomorphic behavior of the ionic liquids [C(4)mim][FeCl4] and [C(12)mim][FeCl4] JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - The iron-containing ionic liquids 1-butyl-3-methylimidazolium tetrachloroferrate(III) [C(4)mim][FeCl4] and 1-dodecyl-3-methylimidazolium tetrachloroferrate(III) [C(12)mim][FeCl4] exhibit a thermally induced demixing with water (thermomorphism). The phase separation temperature varies with IL weight fraction in water and can be tuned between 100 degrees C and room temperature. The reversible lower critical solution temperature (LCST) is only observed at IL weight fractions below ca. 35% in water. UV/Vis, IR, and Raman spectroscopy along with elemental analysis prove that the yellow-brown liquid phase recovered after phase separation is the starting IL [C(4)mim][FeCl4] and [C(12)mim][FeCl4], respectively. Photometry and ICP-OES show that about 40% of iron remains in the water phase upon phase separation. Although the process is thus not very efficient at the moment, the current approach is the first example of an LCST behavior of a metal-containing IL and therefore, although still inefficient, a prototype for catalyst removal or metal extraction. KW - imidazolium KW - ionic liquids KW - phase transitions KW - Raman spectroscopy KW - thermomorphism Y1 - 2011 U6 - https://doi.org/10.1002/cphc.201000808 SN - 1439-4235 VL - 12 IS - 2 SP - 364 EP - 368 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wischerhoff, Erik A1 - Badi, Nezha A1 - Laschewsky, André A1 - Lutz, Jean-Francois ED - Börner, Hans Gerhard ED - Lutz, JF T1 - Smart polymer surfaces concepts and applications in biosciences JF - Advances in polymer science = Fortschritte der Hochpolymeren-Forschung JF - Advances in Polymer Science N2 - Stimuli-responsive macromolecules (i.e., pH-, thermo-, photo-, chemo-, and bioresponsive polymers) have gained exponential importance in materials science, nanotechnology, and biotechnology during the last two decades. This chapter describes the usefulness of this class of polymer for preparing smart surfaces (e.g., modified planar surfaces, particles surfaces, and surfaces of three-dimensional scaffolds). Some efficient pathways for connecting these macromolecules to inorganic, polymer, or biological substrates are described. In addition, some emerging bioapplications of smart polymer surfaces (e.g., antifouling surfaces, cell engineering, protein chromatography, tissue engineering, biochips, and bioassays) are critically discussed. KW - Antifouling surfaces KW - Bioactive surfaces KW - Biocompatible polymers KW - Bioseparation KW - Cell engineering KW - Polymer-modified surfaces KW - Stimuli-responsive polymers Y1 - 2011 SN - 978-3-642-20154-7 U6 - https://doi.org/10.1007/12_2010_88 SN - 0065-3195 VL - 240 IS - 1 SP - 1 EP - 33 PB - Springer CY - Berlin ER - TY - JOUR A1 - Wirth, Jonas A1 - Monturet, Serge A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - Adsorption and (photo-) electrochemical splitting of water on rutile ruthenium dioxide JF - epl : a letters journal exploring the frontiers of physics N2 - In this work, the adsorption and splitting of the water molecule by light and/or an external potential is investigated in the frame of (photo-) electrochemical cells using a rutile ruthenium dioxide anode. With the help of periodic density functional calculations, the adsorbed structures of H(2)O and some radicals involved in the splitting process (O, OH, OOH) are obtained and compared with the available experimental results. On the basis of these electronic-structure calculations, we use a method to calculate the stability of the reaction intermediates and conclude on the thermodynamical possibility of the water splitting reaction at the surface. We demonstrate that a moderate overpotential of 0.64 V is required for the reaction to take place at the RuO(2)(110) surface. Y1 - 2011 U6 - https://doi.org/10.1209/0295-5075/93/68001 SN - 0295-5075 VL - 93 IS - 6 PB - EDP Sciences CY - Mulhouse ER -