@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{BullerLaschewskyLutzetal.2011, author = {Buller, Jens and Laschewsky, Andr{\´e} and Lutz, Jean-Francois and Wischerhoff, Erik}, title = {Tuning the lower critical solution temperature of thermoresponsive polymers by biospecific recognition}, series = {Polymer Chemistry}, volume = {2}, journal = {Polymer Chemistry}, number = {7}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c1py00001b}, pages = {1486 -- 1489}, year = {2011}, abstract = {A thermosensitive statistical copolymer based on oligo(ethylene glycol) methacrylates incorporating biotin was synthesized by free radical copolymerisation. The influence of added avidin on its thermoresponsive behaviour was investigated. The specific binding of avidin to the biotinylated copolymers provoked a marked increase of the lower critical solution temperature.}, 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{DodooSteitzLaschewskyetal.2011, author = {Dodoo, S. and Steitz, R. and Laschewsky, Andr{\´e} and von Klitzing, Regine}, title = {Effect of ionic strength and type of ions on the structure of water swollen polyelectrolyte multilayers}, 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 = {21}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c0cp01357a}, pages = {10318 -- 10325}, year = {2011}, abstract = {This study addresses the effect of ionic strength and type of ions on the structure and water content of polyelectrolyte multilayers. Polyelectrolyte multilayers of poly(sodium-4-styrene sulfonate) (PSS) and poly(diallyl dimethyl ammonium chloride) (PDADMAC) prepared at different NaF, NaCl and NaBr concentrations have been investigated by neutron reflectometry against vacuum, H2O and D2O. Both thickness and water content of the multilayers increase with increasing ionic strength and increasing ion size. Two types of water were identified, "void water" which fills the voids of the multilayers and does not contribute to swelling but to a change in scattering length density and "swelling water" which directly contributes to swelling of the multilayers. The amount of void water decreases with increasing salt concentration and anion radius while the amount of swelling water increases with salt concentration and anion radius. This is interpreted as a denser structure in the dry state and larger ability to swell in water (sponge) for multilayers prepared from high ionic strengths and/or salt solution of large anions. No exchange of hydration water or replacement of H by D was detected even after eight hours incubation time in water of opposing isotopic composition.}, 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} } @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{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{PrevostWattebledLaschewskyetal.2011, author = {Prevost, Sylvain and Wattebled, Laurent and Laschewsky, Andr{\´e} and Gradzielski, Michael}, title = {Formation of monodisperse charged vesicles in mixtures of cationic gemini surfactants and anionic SDS}, series = {Langmuir}, volume = {27}, journal = {Langmuir}, number = {2}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/la103976p}, pages = {582 -- 591}, year = {2011}, abstract = {The aggregation behavior of catanionics formed by the mixture of cationic geminis derived from dodecyltrimethylammonium chloride (DTAC) and anionic sodium dodecylsulfate (SDS) was studied by means of phase studies and comprehensive small-angle neutron scattering (SANS) experiments at 25 degrees C and 50 mM overall concentration. The results are compared to those for the previously studied SDS + DTAC system. Various gemini spacers of different natures and geometries were used, but all of them had similar lengths: an ethoxy bridge, a double bond, and an aromatic ring binding the two DTACs in three different substitutions (ortho, meta, and para). SANS and SAXS data analysis indicates that the spacer has no large effect on the spheroidal micelles of pure surfactants formed at low concentration in water; however, specific effects appear with the addition of electrolytes. Microstructures formed in the catanionic mixtures are rather strongly dependent on the nature of the spacer. The most important finding is that for the hydrophilic, flexible ethoxy bridge, monodisperse vesicles with a fixed anionic/cationic charge ratio (depending only on the surfactant in excess) are formed. Furthermore, the composition of these vesicles shows that strongly charged aggregates are formed. This study therefore provides new opportunities for developing tailor-made gemini surfactants that allow for the fine tuning of catanionic structures.}, language = {en} } @article{GlatzelLaschewskyLutz2011, author = {Glatzel, Stefan and Laschewsky, Andr{\´e} and Lutz, Jean-Francois}, title = {Well-Defined uncharged polymers with a sharp UCST in water and in physiological milieu}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {44}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {2}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/ma102677k}, pages = {413 -- 415}, year = {2011}, language = {en} } @article{AdelsbergerMeierKollBivigouKoumbaetal.2011, author = {Adelsberger, Joseph and Meier-Koll, Andreas and Bivigou Koumba, Achille Mayelle and Busch, Peter and Holderer, Olaf and Hellweg, Thomas and Laschewsky, Andr{\´e} and M{\"u}ller-Buschbaum, Peter and Papadakis, Christine M.}, title = {The collapse transition and the segmental dynamics in concentrated micellar solutions of P(S-b-NIPAM) diblock copolymers}, 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 = {5-6}, publisher = {Springer}, address = {New York}, issn = {0303-402X}, doi = {10.1007/s00396-011-2382-3}, pages = {711 -- 720}, year = {2011}, abstract = {We investigate concentrated solutions of poly(styrene-b-N-isopropyl acrylamide) (P(S-b-NIPAM)) diblock copolymers in deuterated water (D2O). Both structural changes and the changes of the segmental dynamics occurring upon heating through the lower critical solution temperature (LCST) of PNIPAM are studied using small-angle neutron scattering and neutron spin-echo spectroscopy. The collapse of the micellar shell and the cluster formation of collapsed micelles at the LCST as well as an increase of the segmental diffusion coefficient after crossing the LCST are detected. Comparing to our recent results on a triblock copolymer P(S-b-NIPAM-b-S) [25], we observe that the collapse transition of P(S-b-NIPAM) is more complex and that the PNIPAM segmental dynamics are faster than in P(S-b-NIPAM-b-S).}, language = {en} }