@article{ZehmLaschewskyLiangetal.2011, author = {Zehm, Daniel and Laschewsky, Andr{\´e} and Liang, Hua and Rabe, J{\"u}rgen P.}, title = {Straightforward access to amphiphilic dual bottle brushes by combining RAFT, ATRP, and NMP polymerization in one sequence}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {44}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {24}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/ma2015613}, pages = {9635 -- 9641}, year = {2011}, abstract = {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).}, language = {en} } @article{ZehmLaschewskyHeunemannetal.2011, author = {Zehm, Daniel and Laschewsky, Andr{\´e} and Heunemann, Peggy and Gradzielski, Michael and Prevost, Sylvain and Liang, Hua and Rabe, J{\"u}rgen P. and Lutz, Jean-Francois}, title = {Synthesis and self-assembly of amphiphilic semi-brush and dual brush block copolymers in solution and on surfaces}, series = {Polymer Chemistry}, volume = {2}, journal = {Polymer Chemistry}, number = {1}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c0py00200c}, pages = {137 -- 147}, year = {2011}, abstract = {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.}, language = {en} } @article{ZaupaNeffePierceetal.2011, author = {Zaupa, Alessandro and Neffe, Axel T. and Pierce, Benjamin F. and Lendlein, Andreas and Hofmann, Dieter}, title = {A molecular dynamic analysis of gelatin as an amorphous material Prediction of mechanical properties of gelatin systems}, series = {The international journal of artificial organs}, volume = {34}, journal = {The international journal of artificial organs}, number = {2}, publisher = {Wichtig}, address = {Milano}, issn = {0391-3988}, doi = {10.5301/IJAO.2010.6083}, pages = {139 -- 151}, year = {2011}, abstract = {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.}, language = {en} } @article{YuantenBrummelhuisJungingeretal.2011, author = {Yuan, Jiayin and ten Brummelhuis, Niels and Junginger, Mathias and Xie, Zailai and Lu, Yan and Taubert, Andreas and Schlaad, Helmut}, title = {Diversified applications of chemically modified 1,2-Polybutadiene}, series = {Macromolecular rapid communications}, volume = {32}, journal = {Macromolecular rapid communications}, number = {15}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1022-1336}, doi = {10.1002/marc.201100254}, pages = {1157 -- 1162}, year = {2011}, abstract = {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.}, language = {en} } @article{YinLinker2011, author = {Yin, Jian and Linker, Torsten}, title = {Stereoselective diversity-oriented syntheses of functionalized saccharides from bicyclic carbohydrate 1,2-lactones}, series = {Tetrahedron}, volume = {67}, journal = {Tetrahedron}, number = {13}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2011.01.069}, pages = {2447 -- 2461}, year = {2011}, abstract = {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.}, language = {en} } @article{YarmanNagelGajovicEichelmannetal.2011, author = {Yarman, Aysu and Nagel, Thomas and Gajovic-Eichelmann, Nenad and Fischer, Anna and Wollenberger, Ursula and Scheller, Frieder W.}, title = {Bioelectrocatalysis by Microperoxidase-11 in a Multilayer Architecture of Chitosan Embedded Gold Nanoparticles}, series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, volume = {23}, journal = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis}, number = {3}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1040-0397}, doi = {10.1002/elan.201000535}, pages = {611 -- 618}, year = {2011}, abstract = {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.}, language = {en} } @article{XieWhiteWeberetal.2011, author = {Xie, Zai-Lai and White, Robin J. and Weber, Jens and Taubert, Andreas and Titirici, Magdalena M.}, title = {Hierarchical porous carbonaceous materials via ionothermal carbonization of carbohydrates}, series = {Journal of materials chemistry}, volume = {21}, journal = {Journal of materials chemistry}, number = {20}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {0959-9428}, doi = {10.1039/c1jm00013f}, pages = {7434 -- 7442}, year = {2011}, abstract = {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.}, language = {en} } @article{XieTaubert2011, author = {Xie, Zai-Lai and Taubert, Andreas}, title = {Thermomorphic behavior of the ionic liquids [C(4)mim][FeCl4] and [C(12)mim][FeCl4]}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {12}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {2}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201000808}, pages = {364 -- 368}, year = {2011}, abstract = {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.}, language = {en} } @misc{WischerhoffBadiLaschewskyetal.2011, author = {Wischerhoff, Erik and Badi, Nezha and Laschewsky, Andr{\´e} and Lutz, Jean-Francois}, title = {Smart polymer surfaces concepts and applications in biosciences}, series = {Advances in polymer science = Fortschritte der Hochpolymeren-Forschung}, volume = {240}, journal = {Advances in polymer science = Fortschritte der Hochpolymeren-Forschung}, number = {1}, editor = {B{\"o}rner, Hans Gerhard and Lutz, JF}, publisher = {Springer}, address = {Berlin}, isbn = {978-3-642-20154-7}, issn = {0065-3195}, doi = {10.1007/12_2010_88}, pages = {1 -- 33}, year = {2011}, abstract = {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.}, language = {en} } @article{WirthMonturetKlamrothetal.2011, author = {Wirth, Jonas and Monturet, Serge and Klamroth, Tillmann and Saalfrank, Peter}, title = {Adsorption and (photo-) electrochemical splitting of water on rutile ruthenium dioxide}, series = {epl : a letters journal exploring the frontiers of physics}, volume = {93}, journal = {epl : a letters journal exploring the frontiers of physics}, number = {6}, publisher = {EDP Sciences}, address = {Mulhouse}, issn = {0295-5075}, doi = {10.1209/0295-5075/93/68001}, pages = {6}, year = {2011}, abstract = {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.}, language = {en} } @article{WessigWawrzinekMoellnitzetal.2011, author = {Wessig, Pablo and Wawrzinek, Robert and Moellnitz, Kristian and Feldbusch, Elvira and Schilde, Uwe}, title = {A new class of fluorescent dyes based on 1,3-benzodioxole and [1,3]-dioxolo[4.5-f]benzodioxole}, series = {Tetrahedron letters}, volume = {52}, journal = {Tetrahedron letters}, number = {46}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4039}, doi = {10.1016/j.tetlet.2011.09.058}, pages = {6192 -- 6195}, year = {2011}, abstract = {We report on synthesis and photophysical properties of a new class of fluorescent dyes. They are characterized by large Stokes-shifts, long fluorescence lifetimes in organic solvents and a pronounced dependency of the fluorescence lifetime on the solvent polarity. Also worthy of note is the high bleaching stability. To provide access to biochemical and medical applications a series of derivatives were prepared, which exhibit specific reactivity towards different biologically relevant functional groups (carboxylic acids, amines, maleimides, N-hydroxysuccinimide esters). Furthermore, two alkynes were prepared, which could be used in 'Click' chemistry.}, language = {en} } @article{WessigPickSchilde2011, author = {Wessig, Pablo and Pick, Charlotte and Schilde, Uwe}, title = {First example of an atropselective dehydro-Diels-Alder (ADDA) reaction}, series = {Tetrahedron letters}, volume = {52}, journal = {Tetrahedron letters}, number = {32}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4039}, doi = {10.1016/j.tetlet.2011.06.024}, pages = {4221 -- 4223}, year = {2011}, abstract = {A new concept of a stereoselective synthesis of axially chiral biaryls, formed in the course of the dehydro-Diels-Alder (DDA) reaction, has been disclosed. It is based on asymmetric induction of the newly formed chirality axis by a chirality center, which is present in the two synthesized DDA reactants. Depending on the different length of the linkers joining the alkyne moieties the DDA reaction may be triggered photochemically or thermally, where only the thermal variant was stereoselective.}, language = {en} } @article{WessigPick2011, author = {Wessig, Pablo and Pick, Charlotte}, title = {Photochemical synthesis and properties of axially chiral naphthylpyridines}, series = {Journal of photochemistry and photobiology : A, Chemistry}, volume = {222}, journal = {Journal of photochemistry and photobiology : A, Chemistry}, number = {1}, publisher = {Elsevier}, address = {Lausanne}, issn = {1010-6030}, doi = {10.1016/j.jphotochem.2011.06.006}, pages = {263 -- 265}, year = {2011}, abstract = {Five alkynyl pyridines were prepared and cyclized to naphthylpyridines as the main products in the course of a Photo-Dehydro-Diels-Alder reaction. Four of the final products are axially chiral and the determination of the rotational barrier by DFT calculations, dynamic NMR and H PLC experiments is demonstrated. (C) 2011 Elsevier B.V. All rights reserved.}, language = {en} } @article{WessigMoellnitzKellingetal.2011, author = {Wessig, Pablo and M{\"o}llnitz, Kristian and Kelling, Alexandra and Schilde, Uwe}, title = {Crystal structure of 1r,2c,3c,4t,5t,6t-1,2,3,4,5,6-hexakis-trimethylsilanyloxy-cyclohexane, C24H60O6Si6}, series = {Zeitschrift f{\"u}r Kristallographie : international journal for structural, physical and chemical aspects of crystalline materials ; New crystal structures}, volume = {226}, journal = {Zeitschrift f{\"u}r Kristallographie : international journal for structural, physical and chemical aspects of crystalline materials ; New crystal structures}, number = {2}, publisher = {De Gruyter Oldenbourg}, address = {M{\"u}nchen}, issn = {1433-7266}, doi = {10.1524/ncrs.2011.0105}, pages = {228 -- 230}, year = {2011}, abstract = {C24H60O6Si6, triclinic, P (1) over bar (no. 2), a = 11.307(2) angstrom, b = 12.159(2) angstrom, = 16.576(2) angstrom, alpha = 109.47(1)degrees, beta = 94.64(1)degrees, gamma = 111.65(1)degrees, V = 1942.3 angstrom(3), Z = 2, R-gt(F) = 0.043, wR(ref)(F-2) = 0.118, T = 210 K.}, language = {en} } @article{WessigMatthesPick2011, author = {Wessig, Pablo and Matthes, Annika and Pick, Charlotte}, title = {The photo-dehydro-Diels-Alder (PDDA) reaction}, series = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, volume = {9}, journal = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, number = {22}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1477-0520}, doi = {10.1039/c1ob06066j}, pages = {7599 -- 7605}, year = {2011}, abstract = {The photo-dehydro-Diels-Alder (PDDA) reaction is a valuable extension of the classical Diels-Alder (DA) reaction. The PDDA reaction differs from the DA reaction by the replacement of one of the C-C-double bonds of the diene moiety by a C-C triple bond and by the photochemical triggering of the reaction. This entails that, in contrast to the DA reaction, the PDDA reaction proceeds according to a multistage mechanism with biradicals and cycloallenes as intermediates. The PDDA reaction provides access to a considerable variety of compound classes. For example, 1-phenylnaphthlenes, 1,1'-binaphthyls, N-heterocyclic biaryls, and naphthalenophanes could be obtained by this reaction.}, language = {en} } @article{WessigMatthes2011, author = {Wessig, Pablo and Matthes, Annika}, title = {Preparation of Strained Axially Chiral (1,5)Naphthalenophanes by Photo-dehydro-Diels-Alder Reaction}, series = {Journal of the American Chemical Society}, volume = {133}, journal = {Journal of the American Chemical Society}, number = {8}, publisher = {American Chemical Society}, address = {Washington}, issn = {0002-7863}, doi = {10.1021/ja109118m}, pages = {2642 -- 2650}, year = {2011}, abstract = {The preparation of 10 (1,5)naphthalenophanes (10a-j) by photo-dehydro-Diels-Alder (PDDA) reaction is described. Owing to hindered rotation around the biaryl axis, compounds 10 are axially chiral and the separation of enantiomers by chiral HPLC was demonstrated in three cases (10a,b,e). The absolute configuration of the isolated enantiomers could be unambiguously determined by comparison of calculated and measured circular dichroism (CD) spectra. Furthermore, we analyzed ring strain phenomena of (1,5)naphthalenophanes 10. Depending on the length of the linker units, one can distinguish three classes of naphthalenophanes. Compounds 10a-c are highly strained (E-STR = 7-31 kcal/mol), and the strain is caused by small bond angles in the linker unit and deformation of the naphthalene moiety. Another type of strain is observed if the linker unit becomes relatively long (10g,h) originating from transannular interactions and is comparable with the well-known strain of medium sized rings. The naphthalenophanes 10d-f with a linker length of 10-14 atoms are only marginally strained. To clearly discriminate the different sources of strain, we defined two geometrical parameters (average central dihedral angle delta(C) and naphthalene thickness D-N) and demonstrated that they are well-suited to indicate naphthalene deformation of our naphthalenophanes 10 as well as of ten model naphthalenophanes (I-X) with different linker lengths and linking positions.}, language = {en} } @article{WellertTierschKoetzetal.2011, author = {Wellert, Stefan and Tiersch, Brigitte and Koetz, Joachim and Richardt, Andre and Lapp, Alain and Holderer, Olaf and Gaeb, Juergen and Blum, Marc-Michael and Schulreich, Christoph and Stehle, Ralf and Hellweg, Thomas}, title = {The DFPase from Loligo vulgaris in sugar surfactant-based bicontinuous microemulsions structure, dynamics, and enzyme activity}, series = {European biophysics journal : with biophysics letters ; an international journal of biophysics}, volume = {40}, journal = {European biophysics journal : with biophysics letters ; an international journal of biophysics}, number = {6}, publisher = {Springer}, address = {New York}, issn = {0175-7571}, doi = {10.1007/s00249-011-0689-0}, pages = {761 -- 774}, year = {2011}, abstract = {The enzyme diisopropyl fluorophosphatase (DFPase) from the squid Loligo vulgaris is of great interest because of its ability to catalyze the hydrolysis of highly toxic organophosphates. In this work, the enzyme structure in solution (native state) was studied by use of different scattering methods. The results are compared with those from hydrodynamic model calculations based on the DFPase crystal structure. Bicontinuous microemulsions made of sugar surfactants are discussed as host systems for the DFPase. The microemulsion remains stable in the presence of the enzyme, which is shown by means of scattering experiments. Moreover, activity assays reveal that the DFPase still has high activity in this complex reaction medium. To complement the scattering experiments cryo-SEM was also employed to study the microemulsion structure.}, language = {en} } @phdthesis{Weiss2011, author = {Weiß, Jan}, title = {Synthesis and self-assembly of multiple thermoresponsive amphiphilic block copolymers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53360}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {In the present thesis, the self-assembly of multi thermoresponsive block copolymers in dilute aqueous solution was investigated by a combination of turbidimetry, dynamic light scattering, TEM measurements, NMR as well as fluorescence spectroscopy. The successive conversion of such block copolymers from a hydrophilic into a hydrophobic state includes intermediate amphiphilic states with a variable hydrophilic-to-lipophilic balance. As a result, the self-organization is not following an all-or-none principle but a multistep aggregation in dilute solution was observed. The synthesis of double thermoresponsive diblock copolymers as well as triple thermoresponsive triblock copolymers was realized using twofold-TMS labeled RAFT agents which provide direct information about the average molar mass as well as residual end group functionality from a routine proton NMR spectrum. First a set of double thermosensitive diblock copolymers poly(N-n-propylacrylamide)-b-poly(N-ethylacrylamide) was synthesized which differed only in the relative size of the two blocks. Depending on the relative block lengths, different aggregation pathways were found. Furthermore, the complementary TMS-labeled end groups served as NMR-probes for the self-assembly of these diblock copolymers in dilute solution. Reversible, temperature sensitive peak splitting of the TMS-signals in NMR spectroscopy was indicative for the formation of mixed star-/flower-like micelles in some cases. Moreover, triple thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (A), poly(methoxydiethylene glycol acrylate) (B) and poly(N-ethylacrylamide) (C) were obtained from sequential RAFT polymerization in all possible block sequences (ABC, BAC, ACB). Their self-organization behavior in dilute aqueous solution was found to be rather complex and dependent on the positioning of the different blocks within the terpolymers. Especially the localization of the low-LCST block (A) had a large influence on the aggregation behavior. Above the first cloud point, aggregates were only observed when the A block was located at one terminus. Once placed in the middle, unimolecular micelles were observed which showed aggregation only above the second phase transition temperature of the B block. Carrier abilities of such triple thermosensitive triblock copolymers tested in fluorescence spectroscopy, using the solvatochromic dye Nile Red, suggested that the hydrophobic probe is less efficiently incorporated by the polymer with the BAC sequence as compared to ABC or ACB polymers above the first phase transition temperature. In addition, due to the problem of increasing loss of end group functionality during the subsequent polymerization steps, a novel concept for the one-step synthesis of multi thermoresponsive block copolymers was developed. This allowed to synthesize double thermoresponsive di- and triblock copolymers in a single polymerization step. The copolymerization of different N-substituted maleimides with a thermosensitive styrene derivative (4-vinylbenzyl methoxytetrakis(oxyethylene) ether) led to alternating copolymers with variable LCST. Consequently, an excess of this styrene-based monomer allowed the synthesis of double thermoresponsive tapered block copolymers in a single polymerization step.}, language = {en} } @article{WeissLaschewsky2011, author = {Weiss, Jan and Laschewsky, Andr{\´e}}, title = {Temperature-induced self-assembly of triple-responsive triblock copolymers in aqueous solutions}, series = {Langmuir}, volume = {27}, journal = {Langmuir}, number = {8}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/la200115p}, pages = {4465 -- 4473}, year = {2011}, abstract = {A series of triple-thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (PNPAM, A), poly(methoxydiethylene glycol acrylate) (PMDEGA, B), and poly(N-ethylacrylamide) (PNEAM, C) was synthesized by sequential reversible addition-fragmentation chain transfer polymerizations. Polymers of differing block sequences, ABC, BAC, and ACB, with increasing phase transition temperatures in the order A < B < C were prepared. Their aggregation behavior in dilute aqueous solution was investigated using dynamic light scattering, turbidimetry, and NMR spectroscopy. The self-organization of such polymers was found to dependent strongly on the block sequence. While polymers with a terminal low-LCST (lower critical solution temperature) block undergo aggregation above the first phase transition temperature at 20-25 degrees C, triblock copolymers with the low-LCST block in the middle show aggregation only above the second phase transition. The collapse of the middle block is not sufficient to induce aggregation but produces instead stable, unimolecular micelles with a collapsed middle block, as supported by NMR and fluorescence probe data. Continued heating of all copolymers led to two additional thermal transitions at 40-55 and 70-80 degrees C, which could be correlated to the phase transitions of the B and C blocks, respectively. All polymers show a high tendency for cluster formation, once aggregation is induced. The carrier abilities of the triple responsive triblock copolymers for hydrophobic agents were probed with the solvatochromic fluorescence dye Nile Red. With passing through the first thermal transition, the block copolymers are capable of solubilizing Nile Red. In the case of block copolymers with sequences ABC or ACB, which bear the low-LCST block at one terminus, notable amounts of dye are solubilized already at this stage. In contrast, the hydrophobic probe is much less efficiently incorporated by the BAC triblock copolymer, which forms unimolecular micelles. Only after the collapse of the B block, when reaching the second phase transition at about 45 degrees C, does aggregation occur and solubilization becomes efficient. In the case of ABC and ACB polymers, the hydrophobic probe seems to partition between the originally collapsed A chains and the additional hydrophobic chains formed after the collapse of the less hydrophobic B block.}, language = {en} } @article{WeissBoettcherLaschewsky2011, author = {Weiss, Jan and B{\"o}ttcher, Christoph and Laschewsky, Andr{\´e}}, title = {Self-assembly of double thermoresponsive block copolymers end-capped with complementary trimethylsilyl groups}, series = {Soft matter}, volume = {7}, journal = {Soft matter}, number = {2}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c0sm00531b}, pages = {483 -- 492}, year = {2011}, abstract = {A set of double thermoresponsive diblock copolymers poly(N-n-propylacrylamide)-block-poly(N-ethylacrylamide) (PNPAM-b-PNEAM) was synthesised by sequential reversible addition-fragmentation chain transfer (RAFT) polymerisations. Using a twofold trimethylsilyl (TMS)-labeled RAFT-agent, the relative size of the two blocks was varied. While soluble as unimers below 15 degrees C, all copolymers exhibited thermally induced two-step self-assembly in water, due to distinct lower critical solution temperature (LCST) phase transitions of PNPAM (around 20 degrees C) and PNEAM (around 70 degrees C). Their temperature-dependent self-organisation in dilute aqueous solution was studied by turbidimetry, dynamic light scattering, transmission electron microscopy, and (1)H NMR spectroscopy. The copolymers show distinct, two-step self-organisation behaviour with respect to transition temperatures, aggregate type and size, which can be correlated to the relative lengths of the low and high LCST blocks. For polymers having short blocks with low LCST, the first thermal transition induces the formation of individual micelles. Further heating above the second thermal transition results reversibly either in a shrink of the micelle size or in aggregation of the micelles, with hydrodynamic diameters below 250 nm. In contrast in the case of polymers having a long block with low LCST, the first thermal transition already leads to clusters of micelles, while the second thermal transition makes the clusters shrink. Noteworthy, the twofold TMS-labeled end groups report not only on the molar masses of the polymers, but can simultaneously serve as NMR-probes for the self-assembly process. The signal of the TMS-aryl end group displays a reversible temperature dependent, two-step splitting that is indicative of the self-organisation of the block copolymers.}, language = {en} } @article{WeigelDobryakovKlaumuenzeretal.2011, author = {Weigel, A. and Dobryakov, A. and Klaum{\"u}nzer, Bastian and Sajadi, M. and Saalfrank, Peter and Ernsting, N. P.}, title = {Femtosecond stimulated raman spectroscopy of flavin after optical excitation}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {115}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {13}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp1117129}, pages = {3656 -- 3680}, year = {2011}, abstract = {In blue-light photoreceptors using flavin (BLUF), the signaling state is formed already within several 100 ps after illumination, with only small changes of the absorption spectrum. The accompanying structural evolution can, in principle, be monitored by femtosecond stimulated Raman spectroscopy (FSRS). The method is used here to characterize the excited-state properties of riboflavin and flavin adenine dinucleotide in polar solvents. Raman modes are observed in the range 90-1800 cm(-1) for the electronic ground state S-0 and upon excitation to the S-1 state, and modes >1000 cm(-1) of both states are assigned with the help of quantum-chemical calculations. Line shapes are shown to depend sensitively on resonance conditions. They are affected by wavepacket motion in any of the participating electronic states, resulting in complex amplitude modulation of the stimulated Raman spectra. Wavepackets in S-1 can be marked, and thus isolated, by stimulated-emission pumping with the picosecond Raman pulses. Excited-state absorption spectra are obtained from a quantitative comparison of broadband transient fluorescence and absorption. In this way, the resonance conditions for FSRS are determined. Early differences of the emission spectrum depend on excess vibrational energy, and solvation is seen as dynamic Stokes shift of the emission band. The ne state is evidenced only through changes of emission oscillator strength during solvation. S-1 quenching by adenine is seen with all methods in terms of dynamics, not by spectral intermediates.}, language = {en} } @article{WeberTierschUnterlassetal.2011, author = {Weber, Nancy and Tiersch, Brigitte and Unterlass, Miriam M. and Heilig, Anneliese and Tauer, Klaus}, title = {"Schizomorphic" Emulsion Copolymerization Particles}, series = {Macromolecular rapid communications}, volume = {32}, journal = {Macromolecular rapid communications}, number = {23}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1022-1336}, doi = {10.1002/marc.201100491}, pages = {1925 -- 1929}, year = {2011}, abstract = {Cryo-electron microscopy, atomic force microscopy, and light microscopy investigations provide experimental evidence that amphiphilic emulsion copolymerization particles change their morphology in dependence on concentration. The shape of the particles is spherical at solids content above 1\%, but it changes to rod-like, ring-like, and web-like structures at lower concentrations. In addition, the shape and morphology of these particles at low concentrations are not fixed but very flexible and vary with time between spheres, flexible pearlnecklace structures, and stretched rods.}, language = {en} } @phdthesis{Weber2011, author = {Weber, Nancy}, title = {Die Synthese "schizomorpher" Copolymer - Latexteilchen}, address = {Potsdam}, pages = {119 S.}, year = {2011}, language = {de} } @inproceedings{VukicevicSchreiberBeuermann2011, author = {Vukicevic, Radovan and Schreiber, Ulrike and Beuermann, Sabine}, title = {Azide-terminated poly(vinylidene fluoride) as building block for nanocomposite materials and block copolymers}, series = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, volume = {242}, booktitle = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, number = {16}, publisher = {American Chemical Society}, address = {Washington}, issn = {0065-7727}, pages = {1}, year = {2011}, language = {en} } @article{VukicevicBeuermann2011, author = {Vukicevic, Radovan and Beuermann, Sabine}, title = {Fullerenes decorated with poly(vinylidene fluoride)}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {44}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {8}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/ma102754c}, pages = {2597 -- 2603}, year = {2011}, abstract = {Fullerenes decorated with poly(vinylidene fluoride) (PVDF) were synthesized in a three-step procedure: Iodine transfer polymerization of vinylidene fluoride with C(6)F(12)I(2) as the chain transfer agent was carried out in supercritical carbon dioxide to synthesize iodine-terminated PVDF, which was subsequently transformed to azide-terminated polymer. Finally, azide-terminated PVDF chains were attached to a fullerene core under microwave irradiation at 160 degrees C in 1.5 h. The materials were characterized by NMR, FT-IR, UV/vis, GPC, elemental analysis, and DSC. On average, 4-5 PVDF chains are attached to one C(60) moiety. FT-IR spectra and DSC measurements indicate that the polymer end groups strongly affect the crystallinity of the material. For PVDF with azide end groups and PVDF attached to fullerenes the fraction of the beta polymorph is dominant while alpha polymorphs are almost absent.}, language = {en} } @phdthesis{Vukicevic2011, author = {Vukicevic, Radovan}, title = {Iodine- and azide-terminated poly(vinylidene fluoride) as a building block for the preparation of hybrid materials and block copolymers}, address = {Potsdam}, pages = {122 S.}, year = {2011}, language = {en} } @article{VijayakrishnanIssareeCoriloetal.2011, author = {Vijayakrishnan, Balakumar and Issaree, Arisara and Corilo, Yuri E. and Ferreira, Christina Ramires and Eberlin, Marcos N. and Peter, Martin G.}, title = {MSn of the six isomers of (GlcN)(2)(GlcNAc)(2) aminoglucan tetrasaccharides (diacetylchitotetraoses) rules of fragmentation for the sodiated molecules and application to sequence analysis of hetero-chitooligosaccharides}, series = {Carbohydrate polymers : an international journal devoted to scientific and technological aspects of industrially important polysaccharides}, volume = {84}, journal = {Carbohydrate polymers : an international journal devoted to scientific and technological aspects of industrially important polysaccharides}, number = {2}, publisher = {Elsevier}, address = {Oxford}, issn = {0144-8617}, doi = {10.1016/j.carbpol.2010.04.041}, pages = {713 -- 726}, year = {2011}, abstract = {The six possible isomers of di-N-acetylchitotetraoses [AADD, ADDA, ADAD, DADA, DAAD, and DDAA, where D stands for 2-amino-2-deoxy-3-D-glucose (GlcN) and A for 2-acetamido-2-deoxy-beta-D-glucose (GlcNAc)] were analyzed by ESI(+)-MSn. Collision induced dissociation via MSn experiments were performed for the sodiated molecules of m/z 769 [M+Na](+) for each isomer, and fragments were generated mainly by glycosidic bond and cross-ring cleavages. Rules of fragmentation were then established. A reducing end D residue yields the (O.2)A(4) cross-ring [M-59+Na](+) fragment of m/z 710 as the most abundant, whereas isomers containing a reducing end A prefer to lose water to form the [M-18+Na](+) ion of m/z 751, as well as abundant (O.2)A(4) cross-ring [M-101+Na](+) fragments of m/z 668 and B-3 [M-221+Na](+) ions of m/z 548. MS3 of C- and Y-type ions shows analogous fragmentation behaviour that allows identification of the reducing end next-neighbour residue. Due to gas-phase anchimeric assistance, B-type cleavage between the glycosidic oxygen and the anomeric carbon atom is favoured when the glycon is an A residue. Relative ion abundances are generally in the order B >> C > Y, but may vary depending on the next neighbour towards the non-reducing end. These fragmentation rules were used for partial sequence analysis of hetero-chitooligosaccharides of the composition D(2)A(3), D(3)A(3), D(2)A(4), D(4)A(3), and D(3)A(4).}, language = {en} } @article{VidadalaPimpalpalleLinkeretal.2011, author = {Vidadala, Srinivasa Rao and Pimpalpalle, Tukaram M. and Linker, Torsten and Hotha, Srinivas}, title = {Gold-Catalyzed reactions of 2-C-Branched carbohydrates mild glycosidations and selective anomerizations}, series = {European journal of organic chemistry}, journal = {European journal of organic chemistry}, number = {13}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1434-193X}, doi = {10.1002/ejoc.201100134}, pages = {2426 -- 2430}, year = {2011}, abstract = {2-C-branched methyl glycosides react with various alcohols under gold catalysis to transglycosylated products. The method is applicable for the convenient synthesis of disaccharides. Without nucleophile a selective anomerization occurs, giving first access to alpha-configured 2-C-nitromethyl glycosides. The results are interesting for the mechanism of gold-catalyzed glycosidations.}, language = {en} } @phdthesis{ValverdeSerrano2011, author = {Valverde Serrano, Clara}, title = {Self-assembly behavior in hydrophilic block copolymers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-54163}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Block copolymers are receiving increasing attention in the literature. Reports on amphiphilic block copolymers have now established the basis of their self-assembly behavior: aggregate sizes, morphologies and stability can be explained from the absolute and relative block lengths, the nature of the blocks, the architecture and also solvent selectiveness. In water, self-assembly of amphiphilic block copolymers is assumed to be driven by the hydrophobic. The motivation of this thesis is to study the influence on the self-assembly in water of A b B type block copolymers (with A hydrophilic) of the variation of the hydrophilicity of B from non-soluble (hydrophobic) to totally soluble (hydrophilic). Glucose-modified polybutadiene-block-poly(N-isopropylacrylamide) copolymers were prepared and their self-assembly behavior in water studied. The copolymers formed vesicles with an asymmetric membrane with a glycosylated exterior and poly(N-isopropylacrylamide) on the inside. Above the low critical solution temperature (LCST) of poly(N-isopropylacrylamide), the structure collapsed into micelles with a hydrophobic PNIPAM core and glycosylated exterior. This collapse was found to be reversible. As a result, the structures showed a temperature-dependent interaction with L-lectin proteins and were shown to be able to encapsulate organic molecules. Several families of double hydrophilic block copolymers (DHBC) were prepared. The blocks of these copolymers were biopolymers or polymer chimeras used in aqueous two-phase partition systems. Copolymers based on dextran and poly(ethylene glycol) blocks were able to form aggregates in water. Dex6500-b-PEG5500 copolymer spontaneously formed vesicles with PEG as the "less hydrophilic" barrier and dextran as the solubilizing block. The aggregates were found to be insensitive to the polymer's architecture and concentration (in the dilute range) and only mildly sensitive to temperature. Variation of the block length, yielded different morphologies. A longer PEG chain seemed to promote more curved aggregates following the inverse trend usually observed in amphiphilic block copolymers. A shorter dextran promoted vesicular structures as usually observed for the amphiphilic counterparts. The linking function was shown to have an influence of the morphology but not on the self-assembly capability in itself. The vesicles formed by dex6500-b-PEG5500 showed slow kinetics of clustering in the presence of Con A lectin. In addition both dex6500-b-PEG5500 and its crosslinked derivative were able to encapsulate fluorescent dyes. Two additional dextran-based copolymers were synthesized, dextran-b-poly(vinyl alcohol) and dextran-b-poly(vinyl pyrrolidone). The study of their self-assembly allowed to conclude that aqueous two-phase systems (ATPS) is a valid source of inspiration to conceive DHBCs capable of self-assembling. In the second part the principle was extended to polypeptide systems with the synthesis of a poly(N-hydroxyethylglutamine)-block-poly(ethylene glycol) copolymer. The copolymer that had been previously reported to have emulsifying properties was able to form vesicles by direct dissolution of the solid in water. Last, a series of thermoresponsive copolymers were prepared, dextran-b-PNIPAMm. These polymers formed aggregates below the LCST. Their structure could not be unambiguously elucidated but seemed to correspond to vesicles. Above the LCST, the collapse of the PNIPAM chains induced the formation of stable objects of several hundreds of nanometers in radius that evolved with increasing temperature. The cooling of these solution below LCST restored the initial aggregates. This self-assembly of DHBC outside any stimuli of pH, ionic strength, or temperature has only rarely been described in the literature. This work constituted the first formal attempt to frame the phenomenon. Two reasons were accounted for the self-assembly of such systems: incompatibility of the polymer pairs forming the two blocks (enthalpic) and a considerable solubility difference (enthalpic and entropic). The entropic contribution to the positive Gibbs free energy of mixing is believed to arise from the same loss of conformational entropy that is responsible for "the hydrophobic effect" but driven by a competition for water of the two blocks. In that sense this phenomenon should be described as the "hydrophilic effect".}, language = {en} } @article{UtechtKlamrothSaalfrank2011, author = {Utecht, Manuel Martin and Klamroth, Tillmann and Saalfrank, Peter}, title = {Optical absorption and excitonic coupling in azobenzenes forming self-assembled monolayers a study based on density functional theory}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {13}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {48}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c1cp22793a}, pages = {21608 -- 21614}, year = {2011}, abstract = {Based on the analysis of optical absorption spectra, it has recently been speculated that the excitonic coupling between individual azobenzene-functionalized alkanethiols arranged in a self-assembled monolayer (SAM) on a gold surface could be strong enough to hinder collective trans-cis isomerization-on top of steric hindrance [Gahl et al., J. Am. Chem. Soc., 2010, 132, 1831]. Using models of SAMs of increasing complexity (dimer, linear N-mers, and two-dimensionally arranged N-mers) and density functional theory on the (TD-) B3LYP/6-31G* level, we determine optical absorption spectra, the nature and magnitude of excitonic couplings, and the corresponding spectral shifts. It is found that at inter-monomer distances of about 20 angstrom and above, TD-B3LYP excitation frequencies (and signal intensities) can be well described by the frequently used point-dipole approximation. Further, calculated blue shifts in optical absorption spectra account for the experimental observations made for azobenzene/gold SAMs, and hint to the fact that they can indeed be responsible for reduced switching probability in densely packed self-assembled structures.}, language = {en} } @phdthesis{Unterlass2011, author = {Unterlass, Miriam Margarethe}, title = {From monomer salts and their tectonic crystals to aromatic polyimides : development of neoteric synthesis routes}, address = {Potsdam}, pages = {147 S.}, year = {2011}, language = {en} } @misc{TrollKulkarniWangetal.2011, author = {Troll, K. and Kulkarni, Amit and Wang, W. and Darko, C. and Koumba, A. M. Bivigou and Laschewsky, Andr{\´e} and M{\"u}ller-Buschbaum, Peter and Papadakis, Christine M.}, title = {The collapse transition of poly(styrene-b-(N-isopropyl acrylamide)) diblock copolymers in aqueous solution and in thin films}, series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, volume = {289}, journal = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0303-402X}, doi = {10.1007/s00396-010-2344-1}, pages = {227 -- 227}, year = {2011}, language = {en} } @article{TremblayKlinkuschKlamrothetal.2011, author = {Tremblay, Jean Christophe and Klinkusch, Stefan and Klamroth, Tillmann and Saalfrank, Peter}, title = {Dissipative many-electron dynamics of ionizing systems}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {134}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {4}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.3532410}, pages = {10}, year = {2011}, abstract = {In this paper, we perform many-electron dynamics using the time-dependent configuration-interaction method in its reduced density matrix formulation (rho-TDCI). Dissipation is treated implicitly using the Lindblad formalism. To include the effect of ionization on the state-resolved dynamics, we extend a recently introduced heuristic model for ionizing states to the rho-TDCI method, which leads to a reduced density matrix evolution that is not norm-preserving. We apply the new method to the laser-driven excitation of H(2) in a strongly dissipative environment, for which the state-resolve lifetimes are tuned to a few femtoseconds, typical for dynamics of adsorbate at metallic surfaces. Further testing is made on the laser-induced intramolecular charge transfer in a quinone derivative as a model for a molecular switch. A modified scheme to treat ionizing states is proposed to reduce the computational burden associated with the density matrix propagation, and it is thoroughly tested and compared to the results obtained with the former model. The new approach scales favorably (similar to N(2)) with the number of configurations N used to represent the reduced density matrix in the rho-TDCI method, as compared to a N(3) scaling for the model in its original form.}, language = {en} } @article{Tremblay2011, author = {Tremblay, Jean Christophe}, title = {Laser control of molecular excitations in stochastic dissipative media}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {134}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {17}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.3587093}, pages = {16}, year = {2011}, abstract = {In the present work, ideas for controlling photochemical reactions in dissipative environments using shaped laser pulses are presented. New time-local control algorithms for the stochastic Schrodinger equation are introduced and compared to their reduced density matrix analog. The numerical schemes rely on time-dependent targets for guiding the reaction along a preferred path. The methods are tested on the vibrational control of adsorbates at metallic surfaces and on the ultrafast electron dynamics in a strong dissipative medium. The selective excitation of the specific states is achieved with improved yield when using the new algorithms. Both methods exhibit similar convergence behavior and results compare well with those obtained using local optimal control for the reduced density matrix. The favorable scaling of the methods allows to tackle larger systems and to control photochemical reactions in dissipative media of molecules with many more degrees of freedom.}, language = {en} } @article{TiseanuParvulescuBoutonnetetal.2011, author = {Tiseanu, Carmen and Parvulescu, Vasile I. and Boutonnet, Magali and Cojocaru, Bogdan and Primus, Philipp A. and Teodorescu, Cristian M. and Solans, Conchita and Sanchez Dominguez, Margarita}, title = {Surface versus volume effects in luminescent ceria nanocrystals synthesized by an oil-in-water microemulsion method}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {13}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {38}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c1cp21135h}, pages = {17135 -- 17145}, year = {2011}, abstract = {Pure and europium (Eu3+) doped cerium dioxide (CeO2) nanocrystals have been synthesized by a novel oil-in-water microemulsion reaction method under soft conditions. In-situ X-ray diffraction and RAMAN spectroscopy, high-resolution transmission electron microscopy, UV/Vis diffuse-reflectance and Fourier transform infrared spectroscopy as well as time-resolved photoluminescence spectroscopy were used to characterize the nanaocrystals. The as-synthesized powders are nanocrystalline and have a narrow size distribution centered on 3 nm and high surface area of similar to 250 m(2) g(-1). Only a small fraction of the europium ions substitutes for the bulk, cubic Ce4+ sites in the europium-doped ceria nanocrystals. Upon calcination up to 1000 degrees C, a remarkable high surface area of similar to 120 m(2) g (-1) is preserved whereas an enrichment of the surface Ce4+ relative to Ce3+ ions and relative strong europium emission with a lifetime of similar to 1.8 ms and FWHM as narrow as 10 cm(-1) are measured. Under excitation into the UV and visible spectral range, the europium doped ceria nanocrystals display a variable emission spanning the orange-red wavelengths. The tunable emission is explained by the heterogeneous distribution of the europium dopants within the ceria nanocrystals coupled with the progressive diffusion of the europium ions from the surface to the inner ceria sites and the selective participation of the ceria host to the emission sensitization. Effects of the bulk-doping and impregnation with europium on the ceria host structure and optical properties are also discussed.}, language = {en} } @article{ThuenemannKlobesWielandetal.2011, author = {Thuenemann, Andreas F. and Klobes, Peter and Wieland, Christoph and Bruzzano, Stefano}, title = {On the nanostructure of micrometer-sized cellulose beads}, series = {Analytical \& bioanalytical chemistry}, volume = {401}, journal = {Analytical \& bioanalytical chemistry}, number = {4}, publisher = {Springer}, address = {Heidelberg}, issn = {1618-2642}, doi = {10.1007/s00216-011-5176-z}, pages = {1101 -- 1108}, year = {2011}, abstract = {The analysis of the porosity of materials is an important and challenging field in analytical chemistry. The gas adsorption and mercury intrusion methods are the most established techniques for quantification of specific surface areas, but unfortunately, dry materials are mandatory for their applicability. All porous materials that contain water and other solvents in their functional state must be dried before analysis. In this process, care has to be taken since the removal of solvent bears the risk of an incalculable alteration of the pore structure, especially for soft materials. In the present paper, we report on the use of small-angle X-ray scattering (SAXS) as an alternative analysis method for the investigation of the micro and mesopores within cellulose beads in their native, i.e., water-swollen state; in this context, they represent a typical soft material. We show that even gentle removal of the bound water reduces the specific surface area dramatically from 161 to 109 m(2) g(-1) in cellulose bead sample type MT50 and from 417 to 220 m(2) g(-1) in MT100. Simulation of the SAXS curves with a bimodal pore size distribution model reveals that the smallest pores with radii up to 10 nm are greatly affected by drying, whereas pores with sizes in the range of 10 to 70 nm are barely affected. The SAXS results were compared with Brunauer-Emmett-Teller results from nitrogen sorption measurements and with mercury intrusion experiments.}, language = {en} } @article{ThielKlamrothStrauchetal.2011, author = {Thiel, Kerstin and Klamroth, Tillmann and Strauch, Peter and Taubert, Andreas}, title = {On the interaction of ascorbic acid and the tetrachlorocuprate ion [CuCl4](2-) in CuCl nanoplatelet formation from an ionic liquid precursor (ILP)}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {13}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {30}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c1cp20648f}, pages = {13537 -- 13543}, year = {2011}, abstract = {The formation of CuCl nanoplatelets from the ionic liquid precursor (ILP) butylpyridinium tetrachlorocuprate [C4Py](2)[CuCl4] using ascorbic acid as a reducing agent was investigated. In particular, electron paramagnetic resonance (EPR) spectroscopy was used to evaluate the interaction between ascorbic acid and the Cu(II) ion before reduction to Cu(I). EPR spectroscopy suggests that the [CuCl4](2-) ion in the neat IL is a distorted tetrahedron, consistent with DFT calculations. Addition of ascorbic acid leads to the removal of one chloride from the [CuCl4](2-) anion, as shown by DFT and the loss of symmetry by EPR. DFT furthermore suggests that the most stable adduct is formed when only one hydroxyl group of the ascorbic acid coordinates to the Cu(II) ion.}, language = {en} } @phdthesis{tenBrummelhuis2011, author = {ten Brummelhuis, Niels}, title = {Self-assembly of cross-linked polymer micelles into complex higher-order aggregates}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52320}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {The creation of complex polymer structures has been one of the major research topics over the last couple of decades. This work deals with the synthesis of (block co-)polymers, the creation of complex and stimuli-responsive aggregates by self-assembly, and the cross-linking of these structures. Also the higher-order self-assembly of the aggregates is investigated. The formation of poly-2-oxazoline based micelles in aqueous solution and their simultaneous functionalization and cross-linking using thiol-yne chemistry is e.g. presented. By introducing pH responsive thiols in the core of the micelles the influence of charged groups in the core of micelles on the entire structure can be studied. The charging of these groups leads to a swelling of the core and a decrease in the local concentration of the corona forming block (poly(2-ethyl-2-oxazoline)). This decrease in concentration yields a shift in the cloud point temperature to higher temperatures for this Type I thermoresponsive polymer. When the swelling of the core is prohibited, e.g. by the introduction of sufficient amounts of salt, this behavior disappears. Similar structures can be prepared using complex coacervate core micelles (C3Ms) built through the interaction of weakly acidic and basic polymer blocks. The advantage of these structures is that two different stabilizing blocks can be incorporated, which allows for more diverse and complex structures and behavior of the micelles. Using block copolymers with either a polyanionic or a polycationic block C3Ms could be created with a corona which contains two different soluble nonionic polymers, which either have a mixed corona or a Janus type corona, depending on the polymers that were chosen. Using NHS and EDC the micelles could easily be cross-linked by the formation of amide bonds in the core of the micelles. The higher-order self-assembly behavior of these core cross-linked complex coacervate core micelles (C5Ms) was studied. Due to the cross-linking the micelles are stabilized towards changes in pH and ionic strength, but polymer chains are also no longer able to rearrange. For C5Ms with a mixed corona likely network structures were formed upon the collapse of the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm), whereas for Janus type C5Ms well defined spherical aggregates of micelles could be obtained, depending on the pH of the solution. Furthermore it could be shown that Janus micelles can adsorb onto inorganic nanoparticles such as colloidal silica (through a selective interaction between PEO and the silica surface) or gold nanoparticles (by the binding of thiol end-groups). Asymmetric aggregates were also formed using the streptavidin-biotin binding motive. This is achieved by using three out of the four binding sites of streptavidin for the binding of one three-arm star polymer, end-functionalized with biotin groups. A homopolymer with one biotin end-group can be used to occupy the last position. This binding of two different polymers makes it possible to create asymmetric complexes. This phase separation is theoretically independent of the kind of polymer since the structure of the protein is the driving force, not the intrinsic phase separation between polymers. Besides Janus structures also specific cross-linking can be achieved by using other mixing ratios.}, language = {en} } @phdthesis{Tan2011, author = {Tan, Irene}, title = {Towards greener stationary phases : thermoresponsive and carbonaceous chromatographic supports}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53130}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Polymers which are sensitive towards external physical, chemical and electrical stimuli are termed as 'intelligent materials' and are widely used in medical and engineering applications. Presently, polymers which can undergo a physical change when heat is applied at a certain temperature (cloud point) in water are well-studied for this property in areas of separation chemistry, gene and drug delivery and as surface modifiers. One example of such a polymer is the poly (N-isopropylacrylamide) PNIPAAM, where it is dissolved well in water below 32 oC, while by increasing the temperature further leads to its precipitation. In this work, an alternative polymer poly (2-(2-methoxy ethoxy)ethyl methacrylate-co- oligo(ethylene glycol) methacrylate) (P(MEO2MA-co-OEGMA)) is studied due to its biocompatibility and the ability to vary its cloud points in water. When a layer of temperature responsive polymer was attached to a single continuous porous piece of silica-based material known as a monolith, the thermoresponsive characteristic was transferred to the column surfaces. The hybrid material was demonstrated to act as a simple temperature 'switch' in the separation of a mixture of five steroids under water. Different analytes were observed to be separated under varying column temperatures. Furthermore, more complex biochemical compounds such as proteins were also tested for separation. The importance of this work is attributed to separation processes utilizing environmentally friendly conditions, since harsh chemical environments conventionally used to resolve biocompounds could cause their biological activities to be rendered inactive.}, language = {en} } @article{StojanovicMarkovicKleinpeteretal.2011, author = {Stojanovic, Milovan and Markovic, Rade and Kleinpeter, Erich and Baranac-Stojanovic, Marija}, title = {Endo-Mode cyclizations of vinylogous N-acyliminium ions as a route to the synthesis of condensed thiazolidines}, series = {Tetrahedron}, volume = {67}, journal = {Tetrahedron}, number = {49}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2011.10.011}, pages = {9541 -- 9554}, year = {2011}, abstract = {endo-Mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined as a route to the synthesis of condensed thiazolidines. The scope of these reactions and stereochemical outcome are discussed and explained using quantum chemical calculations.}, language = {en} } @article{StojanovicMarkovicKleinpeteretal.2011, author = {Stojanovic, Milovan and Markovic, Rade and Kleinpeter, Erich and Baranac-Stojanovic, Marija}, title = {endo-Mode cyclizations of vinylogous N-acyliminium ions as a route to the synthesis of condensed thiazolidines}, issn = {0040-4020}, year = {2011}, language = {en} } @article{SkrabaniaMiasnikovaBivigouKoumbaetal.2011, author = {Skrabania, Katja and Miasnikova, Anna and Bivigou Koumba, Achille Mayelle and Zehm, Daniel and Laschewsky, Andr{\´e}}, title = {Examining the UV-vis absorption of RAFT chain transfer agents and their use for polymer analysis}, series = {Polymer Chemistry}, volume = {2}, journal = {Polymer Chemistry}, number = {9}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c1py00173f}, pages = {2074 -- 2083}, year = {2011}, abstract = {The absorption characteristics of a large set of thiocarbonyl based chain transfer agents (CTAs) were studied by UV-vis spectroscopy in order to identify appropriate conditions for exploiting their absorbance bands in end-group analysis of polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerisation. Substitution pattern and solvent polarity were found to affect notably the wavelengths and intensities of the pi-pi*- and n-pi*-transition of the thiocarbonyl bond of dithioester and trithiocarbonate RAFT agents. Therefore, it is advisable to refer in end group analysis to the spectral parameters of low molar mass analogues of the active polymer chain ends, rather than to rely on the specific RAFT agent engaged in the polymerisation. When using appropriate conditions, the quantification of the thiocarbonyl end-groups via the pi-pi* band of the thiocarbonyl moiety around 300-310 nm allows a facile, sensitive and surprisingly precise estimation of the number average molar mass of the polymers produced, without the need of particular end group labels. Moreover, when additional methods for absolute molar mass determination can be applied, the quantification of the thiocarbonyl end-groups by UV-spectroscopy provides a good estimate of the degree of active end group for a given polymer sample.}, language = {en} } @article{ShkilnyySchoeneRumplaschetal.2011, author = {Shkilnyy, Andriy and Sch{\"o}ne, Stefanie and Rumplasch, Claudia and Uhlmann, Annett and Hedderich, Annett and G{\"u}nter, Christina and Taubert, Andreas}, title = {Calcium phosphate mineralization with linear poly(ethylene imine) a time-resolved study}, series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, volume = {289}, journal = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, number = {8}, publisher = {Springer}, address = {New York}, issn = {0303-402X}, doi = {10.1007/s00396-011-2403-2}, pages = {881 -- 888}, year = {2011}, abstract = {We have earlier shown that linear poly(ethylene imine) (LPEI) is an efficient growth modifier for calcium phosphate mineralization from aqueous solution (Shkilnyy et al., Langmuir, 2008, 24 (5), 2102). The current study addresses the growth process and the reason why LPEI is such an effective additive. To that end, the solution pH and the calcium and phosphate concentrations were monitored vs. reaction time using potentiometric, complexometric, and photometric methods. The phase transformations in the precipitates and particle morphogenesis were analyzed by X-ray diffraction and transmission electron microscopy, respectively. All measurements reveal steep decreases of the pH, calcium, and phosphate concentrations along with a rapid precipitation of brushite nanoparticles early on in the reaction. Brushite transforms into hydroxyapatite (HAP) within the first 2 h, which is much faster than what is reported, for example, for calcium phosphate precipitated with poly(acrylic acid). We propose that poly(ethylene imine) acts as a proton acceptor (weak buffer), which accelerates the transformation from brushite to HAP by taking up the protons that are released from the calcium phosphate precipitate during the phase transformation.}, language = {en} } @article{ShainyanSuslovaKleinpeter2011, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Kleinpeter, Erich}, title = {Conformational analysis of N-phenyl- and N-trifyl-4,4-dimethyl-4-silathiane 1-sulfimides}, series = {Journal of physical organic chemistry}, volume = {24}, journal = {Journal of physical organic chemistry}, number = {8}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0894-3230}, doi = {10.1002/poc.1811}, pages = {698 -- 704}, year = {2011}, abstract = {N-Substituted 4,4-dimethyl-4-silathiane 1-sulfimides Me2Si(sic)S=NSO2R [R- Ph (1), CF3 (2)] were studied experimentally by variable temperature dynamic NMR spectroscopy. Low temperature 13 C NMR spectra of the two compounds revealed the frozen ring inversion process and approximately equal content of the axial and equatorial conformers. Calculations of the 4-silathiane derivatives 1, 2 and the model compound [R Me (3)] as well as their carbon analogs, the similarly N-substituted (sic)S=NSO2R thiane 1-sulfimides [R = Ph (4), CF3 (5), Me (6)] at the DFT/B3LYP/6-311G(d, p) level in the gas phase and in chloroform solution using the PCM model at the same level of theory showed a strong dependence of the relative stability of the conformer on the solvent. The electronegative trifluoromethyl group increases the relative stability of the axial conformer.}, language = {en} } @article{SengeRyppaFazekasetal.2011, author = {Senge, Mathias O. and Ryppa, Claudia and Fazekas, Marijana and Zawadzka, Monika and Dahms, Katja}, title = {5,10-A2B2-Type meso-Substituted PorphyrinsuA Unique Class of Porphyrins with a Realigned Dipole Moment}, series = {Chemistry - a European journal}, volume = {17}, journal = {Chemistry - a European journal}, number = {48}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201101934}, pages = {13562 -- 13573}, year = {2011}, abstract = {Current applications in porphyrin chemistry require the use of unsymmetrically substituted porphyrins. Many current industrial interests in optics and biomedicine require systems with either pushpull (electron-donating and -withdrawing groups) or amphiphilic systems (hydrophobic and hydrophilic groups). In this context we present the class of 5,10-A2B2-type porphyrins for which two different substituents are positioned in diagonally opposite meso positions. Thus, the intramolecular dipole moment in these tetrapyrroles is positioned along a beta-beta vector passing through two pyrrole rings. This is opposite to the situation of the frequently used 5,15-A2BC porphyrins for which the dipole moment is oriented along a mesomeso axis. We have elaborated syntheses of the 5,10-A2B2 porphyrins by using transition-metal-catalyzed transformations of 5,10-A2 porphyrins or direct substitutions reactions thereof; this gives the target molecules in 2277\% overall yields. The compounds exhibit interesting structural, spectroscopic, and optical features and can serve as building blocks for new porphyrin arrays and applications.}, language = {en} } @phdthesis{Schwadtke2011, author = {Schwadtke, Ulrike}, title = {Synthese und Charakterisierung von partiell fluorierten Blockcopolymeren}, address = {Potsdam}, pages = {117 S.}, year = {2011}, language = {de} } @phdthesis{Schumacher2011, author = {Schumacher, Soeren}, title = {Saccharide recognition : boronic acids as receptors in polymeric networks}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52869}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {In this thesis entitled "Saccharide Recognition - Boronic acids as Receptors in Polymeric Networks" different aspects of boronic acid synthesis, their analysis and incorporation or attachment to different polymeric networks and characterisation thereof were investigated. The following key aspects were considered: • Provision of a variety of different characterised arylboronic acids and benzoboroxoles • Attachment of certain derivatives to nanoparticles and the characterisation of saccharide binding by means of isothermal titration calorimetry and displacement assay (ARS) to enhance the association constant to saccharides at pH 7.4 • Enhancement of selectivity in polymeric systems by means of molecular imprinting using fructose as template and a polymerisable benzoboroxole as functional monomer for the recognition at pH 7.4 (Joined by a diploma thesis of F. Gr{\"u}neberger) • Development of biomimetic saccharide structures and the development of saccharide (especially glucose and fructose) binding MIPs by using these structures as template molecules. In the first part of the thesis different arylboronic acid derivatives were synthesised and their binding to glucose or fructose was investigated by means of isothermal titration calorimetry (ITC). It could be derived, which is in parallel to the literature, that derivatives bearing a methylhydroxyl-group in ortho-position to the boron (benzoboroxole) exhibit in most cases a two-fold higher association constant compared to the corresponding phenylboronic acid derivative. To gain a deeper understanding NMR spectroscopy and mass spectrometry with the benzoboroxole and glucose or fructose was performed. It could be shown that the exchange rate in terms of NMR time scale is quite slow since in titration experiments new peaks appeared. Via mass spectrometry of a mixture between benzoboroxole and glucose or fructose, different binding stoichiometries could be detected showing that the binding of saccharides is comparable with their binding to phenylboronic acid. In addition, the use of Alizarin Red S as an electrochemical reporter was described for the first time to monitor the saccharide binding to arylboronic acids not only with spectroscopy. Here, the redox behaviour and the displacement were recorded by cyclic voltammograms. In the second part different applications of boronic acids in polymeric networks were investigated. The attachment of benzoboroxoles to nanoparticles was investigated and monitored by means of isothermal titration calorimetry and a colourimetric assay with Alizarin Red S as the report dye. The investigations by isothermal titration calorimetry compared the fructose binding of arylboronic acids and benzoboroxoles coupled to these nanoparticles and "free" in solution. It could be shown that the attached derivatives showed a higher binding constant due to an increasing entropy term. This states for possible multivalent binding combined with a higher water release. Since ITC could not characterise the binding of glucose to these nanoparticles due to experimental restrictions the glucose binding at pH 7.4 was shown with ARS. Here, the displacement of ARS by fructose and also glucose could be followed and consequently these nanoparticles can be used for saccharide determination. Within this investigation also the temperature stability of these nanoparticles was examined and after normal sterilisation procedures (121°C, 20 min.) the binding behaviour was still unchanged. To target the selectivity of the used polymeric networks, molecular imprinting was used as a technique for creating artificial binding pockets on a molecular scale. As functional monomer 3-methacrylamidobenzoboroxole was introduced for the recognition of fructose. In comparison to polymers prepared with vinylphenylboronic acid the benzoboroxole containing polymer had a stronger binding at pH 7.4 which was shown for the first time. In addition, another imprinted polymer was synthesised especially for the recognition of glucose and fructose employing biomimetic saccharide analogues as template molecule. The advantage to use the saccharide analogues is the defined template-functional monomer complex during the polymerisation which is not the case, for example, for glucose-boronic acid interaction. The biomimetic character was proven through structural superimposition of crystal structures of the analogues with already described crystal structures of boronic acid esters of glucose and fructose. A molecularly imprinted polymer was synthesised with vinylphenylboronic acid as the functional monomer to show that both glucose and fructose are able to bind to the polymer which was predicted by the structural similarity of the analogues. The major scientific contributions of this thesis are • the determination of binding constants for some, not yet reported saccharide - boronic acid / benzoboroxole pairs, • the use of ARS as electrochemical reporter for saccharide detection, • the thermodynamic characterisation of a saccharide binding nanoparticle system containing benzoboroxole and functioning at pH 7.4, • the use of a polymerisable benzoboroxole as functional monomer for saccharide recognition in neutral, aqueous environments • and the synthesis and utilisation of biomimetic saccharide analogues as template molecules especially for the development of a glucose binding MIP.}, language = {en} } @inproceedings{SchreiberVukicevicBeuermann2011, author = {Schreiber, Ulrike and Vukicevic, Radovan and Beuermann, Sabine}, title = {Block copolymers of poly(vinylidene fluoride) obtained via 1,3 dipolar cycloaddition}, series = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, volume = {242}, booktitle = {Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS}, publisher = {American Chemical Society}, address = {Washington}, issn = {0065-7727}, pages = {1}, year = {2011}, language = {en} } @article{SchreiberHosemannBeuermann2011, author = {Schreiber, Ulrike and Hosemann, Benjamin and Beuermann, Sabine}, title = {1H,1H,2H,2H-Perfluorodecyl-Acrylate-Containing block copolymers from ARGET ATRP}, series = {Macromolecular chemistry and physics}, volume = {212}, journal = {Macromolecular chemistry and physics}, number = {2}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201000307}, pages = {168 -- 179}, year = {2011}, abstract = {Block copolymers of 1H,1H,2H,2H-perfluorodecyl acrylate (AC8) were obtained from ARGET ATRP. To obtain block copolymers of low dispersity the PAC8 block was synthesized in anisole with a CuBr(2)/PMDETA catalyst in the presence of tin(II) 2-ethylhexanoate as a reducing agent. The PAC8 block was subsequently used as macroinitiator for copolymerization with butyl and tert-butyl acrylate carried out in scCO(2). To achieve catalyst solubility in CO(2) two fluorinated ligands were employed. The formation of block copolymers was confirmed by size exclusion chromatography and DSC.}, language = {en} } @article{SchmidtStaudeKellingetal.2011, author = {Schmidt, Bernd and Staude, Lucia and Kelling, Alexandra and Schilde, Uwe}, title = {A Cross-Metathesis-Conjugate addition route to enantiopure gamma-Butyrolactams and gamma-Lactones from a C-2-Symmetric Precursor}, series = {European journal of organic chemistry}, journal = {European journal of organic chemistry}, number = {9}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1434-193X}, doi = {10.1002/ejoc.201001528}, pages = {1721 -- 1727}, year = {2011}, abstract = {A protected derivative of (3R, 4R)-hexa-1,5-diene-3,4-diol, a conveniently accessible C-2-symmetric building block, undergoes single or double cross metathesis with methyl acryl-ate. The cross metathesis products are amenable to stereoselective conjugate addition reactions and can be converted into either gamma-butyrolactones or gamma-lactams.}, language = {en} }