TY - JOUR A1 - Glatzel, Stefan A1 - Laschewsky, André A1 - Lutz, Jean-Francois T1 - Well-Defined uncharged polymers with a sharp UCST in water and in physiological milieu JF - Macromolecules : a publication of the American Chemical Society Y1 - 2011 U6 - https://doi.org/10.1021/ma102677k SN - 0024-9297 VL - 44 IS - 2 SP - 413 EP - 415 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Buller, Jens A1 - Laschewsky, André A1 - Lutz, Jean-Francois A1 - Wischerhoff, Erik T1 - Tuning the lower critical solution temperature of thermoresponsive polymers by biospecific recognition JF - Polymer Chemistry N2 - 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. Y1 - 2011 U6 - https://doi.org/10.1039/c1py00001b SN - 1759-9954 VL - 2 IS - 7 SP - 1486 EP - 1489 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Troll, K. A1 - Kulkarni, Amit A1 - Wang, W. A1 - Darko, C. A1 - Koumba, A. M. Bivigou A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - The collapse transition of poly(styrene-b-(N-isopropyl acrylamide)) diblock copolymers in aqueous solution and in thin films T2 - Colloid and polymer science : official journal of the Kolloid-Gesellschaft Y1 - 2011 U6 - https://doi.org/10.1007/s00396-010-2344-1 SN - 0303-402X VL - 289 IS - 2 SP - 227 EP - 227 PB - Springer CY - New York ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Meier-Koll, Andreas A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - The collapse transition and the segmental dynamics in concentrated micellar solutions of P(S-b-NIPAM) diblock copolymers JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - 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). KW - Block copolymers KW - Responsive polymers KW - Small-angle neutron scattering KW - Neutron spin-echo spectroscopy Y1 - 2011 U6 - https://doi.org/10.1007/s00396-011-2382-3 SN - 0303-402X VL - 289 IS - 5-6 SP - 711 EP - 720 PB - Springer CY - New York ER - TY - JOUR A1 - Weiss, Jan A1 - Laschewsky, André T1 - Temperature-induced self-assembly of triple-responsive triblock copolymers in aqueous solutions JF - Langmuir N2 - 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. Y1 - 2011 U6 - https://doi.org/10.1021/la200115p SN - 0743-7463 VL - 27 IS - 8 SP - 4465 EP - 4473 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zehm, Daniel A1 - Laschewsky, André A1 - Heunemann, Peggy A1 - Gradzielski, Michael A1 - Prevost, Sylvain A1 - Liang, Hua A1 - Rabe, Jürgen P. A1 - Lutz, Jean-Francois T1 - Synthesis and self-assembly of amphiphilic semi-brush and dual brush block copolymers in solution and on surfaces JF - Polymer Chemistry N2 - The combination of two techniques of controlled free radical polymerization, namely the reversible addition fragmentation chain transfer (RAFT) and the atom transfer radical polymerization (ATRP) techniques, together with the use of a macromonomer allowed the synthesis of symmetrical triblock copolymers, designed as amphiphilic dual brushes. One type of brush was made of poly(n-butyl acrylate) as soft hydrophobic block, i.e. characterized by a low glass transition temperature, while the other one was made of hydrophilic poly(ethylene glycol) (PEG). The new triblock polymers represent "giant surfactants" according to their molecular architecture. The hydrophobic and hydrophilic blocks microphase separate in the bulk. In aqueous solution, they aggregate into globular micellar aggregates, their size being determined by the length of the stretched polymer molecules. As determined by the combination of various scattering techniques for the dual brush copolymer, a rather compact structure is formed, which is dominated by the large hydrophobic poly(n-butyl acrylate) block. The aggregation number for the dual brush is about 10 times larger than for the "semi-brush" precursor copolymer, due to the packing requirements for the much bulkier hydrophobic core. On mica surfaces the triblock copolymers adsorb with worm-like backbones and stretched out side chains. Y1 - 2011 U6 - https://doi.org/10.1039/c0py00200c SN - 1759-9954 VL - 2 IS - 1 SP - 137 EP - 147 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zehm, Daniel A1 - Laschewsky, André A1 - Liang, Hua A1 - Rabe, Jürgen P. T1 - Straightforward access to amphiphilic dual bottle brushes by combining RAFT, ATRP, and NMP polymerization in one sequence JF - Macromolecules : a publication of the American Chemical Society N2 - Molecular brush diblock copolymers were synthesized by the orthogonal overlay of the RAFT (reversible addition-fragmentation chain transfer), the ATRP (atom transfer radical polymerization), and the NMP (nitroxide-mediated polymerization) techniques. This unique combination enabled the synthesis of the complex amphiphilic polymers without the need of postpolymerization modifications, using a diblock copolymer intermediate made from two selectively addressable inimers and applying a sequence of four controlled free radical polymerization steps in total. The resulting polymers are composed of a thermosensitive poly(N-isopropylacrylamide) brush as hydrophilic block and a polystyrene brush as hydrophobic block, thus translating the structure of the established amphiphilic diblock copolymers known as macro surfactants to the higher size level of "giant surfactants". The dual molecular brushes and the aggregates formed on ultra flat solid substrates were visualized by scanning force microscopy (SFM). Y1 - 2011 U6 - https://doi.org/10.1021/ma2015613 SN - 0024-9297 VL - 44 IS - 24 SP - 9635 EP - 9641 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kristen-Hochrein, Nora A1 - Laschewsky, André A1 - Miller, Reinhard A1 - von Klitzing, Regine T1 - Stability of foam Films of oppositely charged polyelectrolyte/surfactant mixtures - effect of isoelectric point JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - In the present paper, the influence of the surfactant concentration and the degree of charge of a polymer on foam film properties of oppositely charged polyelectrolyte/surfactant mixtures has been investigated. To verify the assumption that the position of the isoelectric point (IEP) does not change the character of the foam film stabilities, the position of the IEP of the polyelectrolyte/surfactant mixtures has been shifted in two different ways. Within the first series of experiments, the foam. film properties were studied using a fixed surfactant concentration of 3 x 10(-5) M in the mixture. Due to the low surfactant concentration, this is a rather dilute system. In the second approach, a copolymer of nonionic and ionic monomer units was Used to lower the charge density of the polymer. This gave rise to additional interactions between the polyelectrolyte and the surfactant, which makes the description of the foam film behavior more complex. In both systems, the same characteristics of the foam film stabilities were found: The foam film stability is reduced toward the IEP of the system, followed by a destabilization around the IEP., At polyelectrolyte concentrations above the IEP, foam films are very stable. However, the concentration range where unstable films were formed was rather broad, and the mechanisms leading to the destabilization had different origins. The results were compared with former findings on PAMPS/C(14)TAB mixtures with an IEP of 10(-4)M.(1) Y1 - 2011 U6 - https://doi.org/10.1021/jp206964k SN - 1520-6106 VL - 115 IS - 49 SP - 14475 EP - 14483 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wischerhoff, Erik A1 - Badi, Nezha A1 - Laschewsky, André A1 - Lutz, Jean-Francois ED - Börner, Hans Gerhard ED - Lutz, JF T1 - Smart polymer surfaces concepts and applications in biosciences JF - Advances in polymer science = Fortschritte der Hochpolymeren-Forschung JF - Advances in Polymer Science N2 - Stimuli-responsive macromolecules (i.e., pH-, thermo-, photo-, chemo-, and bioresponsive polymers) have gained exponential importance in materials science, nanotechnology, and biotechnology during the last two decades. This chapter describes the usefulness of this class of polymer for preparing smart surfaces (e.g., modified planar surfaces, particles surfaces, and surfaces of three-dimensional scaffolds). Some efficient pathways for connecting these macromolecules to inorganic, polymer, or biological substrates are described. In addition, some emerging bioapplications of smart polymer surfaces (e.g., antifouling surfaces, cell engineering, protein chromatography, tissue engineering, biochips, and bioassays) are critically discussed. KW - Antifouling surfaces KW - Bioactive surfaces KW - Biocompatible polymers KW - Bioseparation KW - Cell engineering KW - Polymer-modified surfaces KW - Stimuli-responsive polymers Y1 - 2011 SN - 978-3-642-20154-7 U6 - https://doi.org/10.1007/12_2010_88 SN - 0065-3195 VL - 240 IS - 1 SP - 1 EP - 33 PB - Springer CY - Berlin ER - TY - JOUR A1 - Weiss, Jan A1 - Böttcher, Christoph A1 - Laschewsky, André T1 - Self-assembly of double thermoresponsive block copolymers end-capped with complementary trimethylsilyl groups JF - Soft matter N2 - 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. Y1 - 2011 U6 - https://doi.org/10.1039/c0sm00531b SN - 1744-683X VL - 7 IS - 2 SP - 483 EP - 492 PB - Royal Society of Chemistry CY - Cambridge ER -