TY - JOUR A1 - Skrabania, Katja A1 - Miasnikova, Anna A1 - Bivigou Koumba, Achille Mayelle A1 - Zehm, Daniel A1 - Laschewsky, André T1 - Examining the UV-vis absorption of RAFT chain transfer agents and their use for polymer analysis JF - Polymer Chemistry N2 - 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. Y1 - 2011 U6 - https://doi.org/10.1039/c1py00173f SN - 1759-9954 VL - 2 IS - 9 SP - 2074 EP - 2083 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Prevost, Sylvain A1 - Wattebled, Laurent A1 - Laschewsky, André A1 - Gradzielski, Michael T1 - Formation of monodisperse charged vesicles in mixtures of cationic gemini surfactants and anionic SDS JF - Langmuir N2 - 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. Y1 - 2011 U6 - https://doi.org/10.1021/la103976p SN - 0743-7463 VL - 27 IS - 2 SP - 582 EP - 591 PB - American Chemical Society CY - Washington ER - 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 - 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 - Marsat, Jean-Noel A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Berlepsch, Hans V. A1 - Boettcher, Christoph A1 - Laschewsky, André T1 - Self-Assembly into multicompartment micelles and selective solubilization by Hydrophilic-Lipophilic-Fluorophilic block copolymers JF - Macromolecules : a publication of the American Chemical Society N2 - Amphiphilic linear ternary block copolymers (ABC) were synthesized in three consecutive steps by the reversible addition fragmentation chain transfer (RAFT) method. Using oligo(ethylene oxide) monomethyl ether acrylate, benzyl acrylate, and 1H,1H-perfluorobutyl acrylate monomers, the triblock copolymers consist of a hydrophilic (A), a lipophilic (B), and a fluorophilic (C) block. The block sequence of the triphilic copolymers was varied systematically to provide all possible variations: ABC, ACB, and BAC. All blocks have glass transition temperatures below 0 degrees C. Self-assembly into spherical micellar aggregates was observed in aqueous solution, where hydrophobic cores undergo local phase separation into various ultrastructures as shown by cryogenic transmission electron microscopy (cryo-TEM). Selective solubilization of substantial quantities of hydrocarbon and fluorocarbon low molar mass compounds by the lipophilic and fluorophilic block, respectively, is demonstrated. Y1 - 2011 U6 - https://doi.org/10.1021/ma200032j SN - 0024-9297 VL - 44 IS - 7 SP - 2092 EP - 2105 PB - American Chemical Society CY - Washington 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 - 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 - 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 - Herfurth, Christoph A1 - Voll, Dominik A1 - Buller, Jens A1 - Weiss, Jan A1 - Barner-Kowollik, Christopher A1 - Laschewsky, André T1 - Radical addition fragmentation chain transfer (RAFT) polymerization of ferrocenyl (meth)acrylates JF - Journal of polymer science : A, Polymer chemistry N2 - We report on the controlled free radical homopolymerization of 1-ferrocenylethyl acrylate as well as of three new ferrocene bearing monomers, namely 4-ferrocenylbutyl acrylate, 2-ferrocenylamido-2-methylpropyl acrylate, and 4-ferrocenylbutyl methacrylate, by the RAFT technique. For comparison, the latter monomer was polymerized using ATRP, too. The ferrocene containing monomers were found to be less reactive than their analogues free of ferrocene. The reasons for the low polymerizability are not entirely clear. As the addition of free ferrocene to the reaction mixture did not notably affect the polymerizations, sterical hindrance by the bulky ferrocene moiety fixed on the monomers seems to be the most probable explanation. Molar masses found for 1-ferrocenylethyl acrylate did not exceed 10,000 g mol(-1), while for 4-ferrocenylbutyl (meth) acrylate molar masses of 15,000 g mol(-1) could be obtained. With PDIs as low as 1.3 in RAFT polymerization of the monomers, good control over the polymerization was achieved. KW - ferrocene KW - living radical polymerization (LRP) KW - monomers KW - radical addition fragmentation chain transfer (RAFT) KW - radical polymerization KW - redox polymers KW - synthesis Y1 - 2012 U6 - https://doi.org/10.1002/pola.24994 SN - 0887-624X VL - 50 IS - 1 SP - 108 EP - 118 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Weiss, Jan A1 - Li, Ang A1 - Wischerhoff, Erik A1 - Laschewsky, André T1 - Water-soluble random and alternating copolymers of styrene monomers with adjustable lower critical solution temperature JF - Polymer Chemistry N2 - Random copolymers of 4-vinylbenzyl tri(oxyethylene) and tetra(oxyethylene) ethers, as well as alternating copolymers of 4-vinylbenzyl methoxytetra(oxyethylene) ether and a series of N-substituted maleimides, were synthesised by conventional free radical polymerisation, reversible addition fragmentation chain transfer (RAFT) and atom transfer radical polymerisation (ATRP). Their thermosensitive behaviour in aqueous solution was studied by turbidimetry and dynamic light scattering. Depending on the copolymer composition, a LCST type phase transition was observed in water. The transition temperature of the obtained random as well as alternating copolymers could be varied within a broad temperature window. In the case of the random copolymers, transition temperatures could be easily fine-tuned, as they showed a linear dependence on the copolymer composition, and were additionally modified by the nature of the polymer end-groups. Alternating copolymers were extremely versatile for implementing a broad range of variations of the phase transition temperatures. Further, while alternating copolymers derived from 4-vinylbenzyl methoxytetra(oxyethylene) ether and maleimides with small hydrophobic side chains underwent macroscopic phase separation when dissolved in water and heated above their cloud point, the incorporation of maleimides bearing larger hydrophobic substituents resulted in the formation of mesoglobules above the phase transition temperature, with hydrodynamic diameters of less than 100 nm. Y1 - 2012 U6 - https://doi.org/10.1039/c1py00422k SN - 1759-9954 VL - 3 IS - 2 SP - 352 EP - 361 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Kaune, Gunar A1 - Rawolle, Monika A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Müller-Buschbaum, Peter T1 - Switching kinetics of thin thermo-responsive hydrogel films of poly(monomethoxy-diethyleneglycol-acrylate) probed with in situ neutron reflectivity JF - Soft matter N2 - The switching kinetics of thin thermo-responsive hydrogel films of poly(monomethoxy-diethyleneglycol-acrylate) (PMDEGA) are investigated. Homogeneous and smooth PMDEGA films with a thickness of 35.9 nm are prepared on silicon substrates by spin coating. As probed with white light interferometry, PMDEGA films with a thickness of 35.9 nm exhibit a phase transition temperature of the lower critical solution temperature (LCST) type of 40 degrees C. In situ neutron reflectivity is performed to investigate the thermo-responsive behavior of these PMDEGA hydrogel films in response to a sudden thermal stimulus in deuterated water vapor atmosphere. The collapse transition proceeds in a complex way which can be seen as three steps. The first step is the shrinkage of the initially swollen film by a release of water. In the second step the thickness remains constant with water molecules embedded in the film. In the third step, perhaps due to a conformational rearrangement of the collapsed PMDEGA chains, water is reabsorbed from the vapor atmosphere, thereby giving rise to a relaxation process. Both the shrinkage and relaxation processes can be described by a simple model of hydrogel deswelling. Y1 - 2012 U6 - https://doi.org/10.1039/c2sm25401h SN - 1744-683X VL - 8 IS - 19 SP - 5241 EP - 5249 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Herfurth, Christoph A1 - de Molina, Paula Malo A1 - Wieland, Christoph A1 - Rogers, Sarah A1 - Gradzielski, Michael A1 - Laschewsky, André T1 - One-step RAFT synthesis of well-defined amphiphilic star polymers and their self-assembly in aqueous solution JF - Polymer Chemistry N2 - Multifunctional chain transfer agents for RAFT polymerisation were designed for the one-step synthesis of amphiphilic star polymers. Thus, hydrophobically end-capped 3- and 4-arm star polymers, as well as linear ones for reference, were made of the hydrophilic monomer N,N-dimethylacrylamide (DMA) in high yield with molar masses up to 150 000 g mol(-1), narrow molar mass distribution (PDI <= 1.2) and high end group functionality (similar to 90%). The associative telechelic polymers form transient networks of interconnected aggregates in aqueous solution, thus acting as efficient viscosity enhancers and rheology modifiers, eventually forming hydrogels. The combination of dynamic light scattering (DLS), small angle neutron scattering (SANS) and rheology experiments revealed that several molecular parameters control the structure and therefore the physical properties of the aggregates. In addition to the size of the hydrophilic block (maximum length for connection) and the length of the hydrophobic alkyl chain ends (stickiness), the number of arms (functionality) proved to be a key parameter. Y1 - 2012 U6 - https://doi.org/10.1039/c2py20126g SN - 1759-9954 VL - 3 IS - 6 SP - 1606 EP - 1617 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Metwalli, Ezzeldin A1 - Diethert, Alexander A1 - Grillo, Isabelle A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of collapse transition and cluster formation in a thermoresponsive micellar solution of P(S-b-NIPAM-b-S) induced by a temperature jump JF - Macromolecular rapid communications N2 - Structural changes at the intra- as well as intermicellar level were induced by the LCST-type collapse transition of poly(N-isopropyl acrylamide) in ABA triblock copolymer micelles in water. The distinct process kinetics was followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while a micellar solution of a triblock copolymer, consisting of two short deuterated polystyrene endblocks and a long thermoresponsive poly(N-isopropyl acrylamide) middle block, was heated rapidly above its cloud point. A very fast collapse together with a multistep aggregation behavior is observed. The findings of the transition occurring at several size and time levels may have implications for the design and application of such thermoresponsive self-assembled systems. KW - polymer physics KW - thermoresponsive polymers KW - small-angle neutron scattering KW - time-resolved measurements Y1 - 2012 U6 - https://doi.org/10.1002/marc.201100631 SN - 1022-1336 VL - 33 IS - 3 SP - 254 EP - 259 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Miasnikova, Anna A1 - Laschewsky, André A1 - De Paoli, Gabriele A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter A1 - Funari, Sergio S. T1 - Thermoresponsive Hydrogels from Symmetrical Triblock Copolymers Poly(styrene-block-(methoxy diethylene glycol acrylate)-block-styrene) JF - Langmuir N2 - A series of symmetrical, thermo-responsive triblock copolymers was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization, and studied in aqueous solution with respect to their ability to form hydrogels. Triblock copolymers were composed of two identical, permanently hydrophobic outer blocks, made of low molar mass polystyrene, and of a hydrophilic inner block of variable length, consisting of poly(methoxy diethylene glycol acrylate) PMDEGA. The polymers exhibited a LCST-type phase transition in the range of 20-40 degrees C, which markedly depended on molar mass and concentration. Accordingly, the triblock copolymers behaved as amphiphiles at low temperatures, but became water-insoluble at high temperatures. The temperature dependent self-assembly of the amphiphilic block copolymers in aqueous solution was studied by turbidimetry and rheology at concentrations up to 30 wt %, to elucidate the impact of the inner thermoresponsive block on the gel properties. Additionally, small-angle X-ray scattering (SAXS) was performed to access the structural changes in the gel with temperature. For all polymers a gel phase was obtained at low temperatures, which underwent a gel-sol transition at intermediate temperatures, well below the cloud point where phase separation occurred. With increasing length of the PMDEGA inner block, the gel-sol transition shifts to markedly lower concentrations, as well as to higher transition temperatures. For the longest PMDEGA block studied (DPn about 450), gels had already formed at 3.5 wt % at low temperatures. The gel-sol transition of the hydrogels and the LCST-type phase transition of the hydrophilic inner block were found to be independent of each other. Y1 - 2012 U6 - https://doi.org/10.1021/la204665q SN - 0743-7463 VL - 28 IS - 9 SP - 4479 EP - 4490 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Laschewsky, André T1 - Recent trends in the synthesis of polyelectrolytes JF - Current opinion in colloid & interface science : current chemistry N2 - Recent developments in the synthesis of polyelectrolytes are highlighted, with respect to the nature of the ionic groups, the polymer backbones, synthetic methods, and additional functionality given to the polyelectrolytes. In fact, the synthesis of new polyelectrolytes is mostly driven by material aspects, currently. The article pays particular attention to strong polyelectrolytes, and the new methods of controlled polymerization. These methods and the so-called click reactions have enabled novel designs of polyelectrolytes. Nevertheless, the polymerization of unprotected ionic monomers is still challenging and limits the synthetic possibilities. The structural aspects are complemented by considerations with respect to the aspired uses of the new polyelectrolytes. KW - Polyelectrolytes KW - Synthesis KW - Ionic monomers KW - Controlled polymerization KW - "click" chemistry Y1 - 2012 U6 - https://doi.org/10.1016/j.cocis.2011.08.001 SN - 1359-0294 VL - 17 IS - 2 SP - 56 EP - 63 PB - Elsevier CY - London ER - TY - JOUR A1 - Weiss, Jan A1 - Laschewsky, André T1 - One-step synthesis of amphiphilic, double thermoresponsive diblock copolymers JF - Macromolecules : a publication of the American Chemical Society N2 - The copolymerization of an excess of a functionalized styrene monomer, 4-vinylbenzyl methoxytetrakis(oxyethylene) ether, with various N-substituted maleimides yields tapered diblock copolymers in a one-step procedure, when applying reversible deactivation radical polymerization (RDRP) methods, such as ATRP and RAFT. The particular chemical structure of the diblock copolymers prepared results in reversible temperature-responsive two-step aggregation behavior in dilute aqueous solution. In this way, a double hydrophilic block copolymer is transformed step by step into an amphiphilic macrosurfactant, and finally into a double hydrophobic copolymer, as followed by turbidimetry and dynamic light scattering. Copolymers in which the maleimide repeat units bear short hydrophobic side chains are freely water-soluble at low temperature and form micellar aggregates above their cloud point. Further heating above the phase transition temperature of the second block results in secondary aggregation. Copolymers with maleimides that bear strongly hydrophobic substituents undergo two thermally induced aggregation steps upon heating, too, but show in addition intramolecular hydrophobic association in water already at low temperatures, similar to the behavior of polysoaps. Y1 - 2012 U6 - https://doi.org/10.1021/ma300285y SN - 0024-9297 VL - 45 IS - 10 SP - 4158 EP - 4165 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Fandrich, Artur A1 - Buller, Jens A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Lisdat, Fred T1 - Electrochemical detection of the thermally induced phase transition of a thin stimuli-responsive polymer film JF - ChemPhysChem : a European journal of chemical physics and physical chemistry KW - cyclic voltammetry KW - electrochemical impedance spectroscopy KW - polymers KW - surface chemistry KW - surface plasmon resonance Y1 - 2012 U6 - https://doi.org/10.1002/cphc.201100924 SN - 1439-4235 VL - 13 IS - 8 SP - 2020 EP - 2023 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Miasnikova, Anna A1 - Laschewsky, André T1 - Influencing the phase transition temperature of poly(methoxy diethylene glycol acrylate) by molar mass, end groups, and polymer architecture JF - Journal of polymer science : A, Polymer chemistry N2 - The easily accessible, but virtually overlooked monomer methoxy diethylene glycol acrylate was polymerized by the RAFT method using monofunctional, difunctional, and trifunctional trithiocarbonates to afford thermoresponsive polymers exhibiting lower critical solution temperature-type phase transitions in aqueous solution. The use of the appropriate RAFT agent allowed for the preparation and systematic variation of polymers with defined molar mass, end-groups, and architecture, including amphiphilic diblock, symmetrical triblock, and triarm star-block copolymers, containing polystyrene as permanently hydrophobic constituent. The cloud points (CPs) of the various polymers proved to be sensitive to all varied parameters, namely molar mass, nature, and number of the end-groups, and the architecture, up to relatively high molar masses. Thus, CPs of the polymers can be adjusted within the physiological interesting range of 2040 degrees C. Remarkably, CPs increased with the molar mass, even when hydrophilic end groups were attached to the polymers. KW - water-soluble polymers KW - diblock copolymers KW - triblock copolymers KW - star-block copolymers KW - reversible addition fragmentation chain transfer (RAFT) KW - LCST KW - stimuli-sensitive polymers Y1 - 2012 U6 - https://doi.org/10.1002/pola.26116 SN - 0887-624X VL - 50 IS - 16 SP - 3313 EP - 3323 PB - Wiley-Blackwell CY - Hoboken ER - TY - CHAP A1 - Laschewsky, André A1 - Liang, Hua A1 - Rabe, Jürgen P. A1 - Skrabania, Katja A1 - Stahlhut, Frank A1 - Weiss, Jan A1 - Zehm, Daniel T1 - Molecularly designed polymer colloids From giant surfactants to multicompartment micelles T2 - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS Y1 - 2012 SN - 0065-7727 VL - 244 IS - 32 PB - American Chemical Society CY - Washington ER - TY - CHAP A1 - Laschewsky, André A1 - Herfurth, Christoph A1 - Miasnikova, Anna A1 - Wieland, Christoph A1 - Wischerhoff, Erik A1 - Gradzielski, Michael A1 - de Molina, Paula Malo A1 - Weiss, Jan T1 - Stars and blocks tailoring polymeric rheology modifiers for aqueous media by controlled free radical polymerization T2 - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS Y1 - 2012 SN - 0065-7727 VL - 244 PB - American Chemical Society CY - Washington ER - TY - CHAP A1 - Buller, Jens A1 - Laschewsky, André A1 - Wischerhoff, Erik A1 - Fandrich, Artur A1 - Lisdat, Fred T1 - Smart synthetic macromolecules recognizing proteins T2 - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS Y1 - 2012 SN - 0065-7727 VL - 244 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - de Molina, Paula Malo A1 - Herfurth, Christoph A1 - Laschewsky, André A1 - Gradzielski, Michael T1 - Structure and dynamics of networks in mixtures of hydrophobically modified telechelic multiarm polymers and oil in water microemulsions JF - Langmuir N2 - The structural and dynamical properties of oil-in-water (O/W) microemulsions (MEs) modified with telechelic polymers of different functionality (e.g., number of hydrophobically modified arms, f) were studied by means of dynamic light scattering (DLS), small-angle neutron scattering (SANS), and high frequency rheology measurements as a function of the polymer architecture and the amount of added polymer. For this purpose, we employed tailor-made hydrophobically end-capped poly(N,N-dimethylacrylamide) star polymers of a variable number of endcaps, f, of different alkyl chain lengths, synthesized by the reversible addition-fragmentation chain transfer method. The addition of the different end-capped polymers to an uncharged ME of O/W droplets leads to a large enhancement of the viscosity of the systems. SANS experiments show that the O/W ME droplets are not changed upon the addition of the polymer, and its presence only changes the interdroplet interactions. The viscosity increases largely upon addition of a polymer, and this enhancement depends pronouncedly on the alkyl length of the hydrophobic sticker as it controls the residence time in a ME droplet. Similarly, the high frequency modulus G(0) depends on the amount of added polymer but not on the sticker length. G(0) was found to be directly proportional to f - 1. The onset of network formation is shifted to a lower number of stickers per ME droplet with increasing f, and the network formation becomes more effective. Thus, the dynamics of network formation are controlled by the polymer architecture. The effect on the dynamics seen by DLS is even more pronounced. Upon increasing the polymer concentration, slower relaxation modes appear that become especially pronounced with increasing number of arms. The relaxation dynamics are correlated to the rheological relaxation, and both are controlled by the polymer architecture. Y1 - 2012 U6 - https://doi.org/10.1021/la303673a SN - 0743-7463 VL - 28 IS - 45 SP - 15994 EP - 16006 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Buller, Jens A1 - Laschewsky, André A1 - Wischerhoff, Erik T1 - Photoreactive oligoethylene glycol polymers - versatile compounds for surface modification by thin hydrogel films JF - Soft matter N2 - Solid surfaces are modified using photo-crosslinkable copolymers based on oligo(ethylene glycol) methacrylate (OEGMA) bearing 2-(4-benzoylphenoxy) ethyl methacrylate (BPEM) as a photosensitive crosslinking unit. Thin films of about 100 nm are formed by spin-coating these a priori highly biocompatible copolymers onto silicon substrates. Subsequent UV-irradiation assures immobilization and crosslinking of the hydrogel films. Their stability is controlled by the number of crosslinker units per chain and the molar mass of the copolymers. The swelling of the hydrogel layers, as investigated by ellipsometry, can be tuned by the crosslinker content in the copolymer. If films are built from the ternary copolymers of OEGMA, BPEM and 2-(2-methoxyethoxy) ethyl methacrylate (MEO(2)MA), the hydrogel films exhibit a swelling/deswelling transition of the lower critical solution temperature (LCST) type. The observed thermally induced hydrogel collapse is fully reversible and the onset temperature of the transition can be tuned at will by the copolymer composition. Different from analogously prepared thermo-responsive hydrogel films of photocrosslinked poly(N-isopropylacrylamide), the swelling-deswelling transition occurs more gradually, but shows no hysteresis. Y1 - 2013 U6 - https://doi.org/10.1039/c2sm26879e SN - 1744-683X VL - 9 IS - 3 SP - 929 EP - 937 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Grillo, Isabelle A1 - Kulkarni, Amit A1 - Sharp, Melissa A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of aggregation in micellar solutions of thermoresponsive triblock copolymers - influence of concentration, start and target temperatures JF - Soft matter N2 - In aqueous solution, symmetric triblock copolymers with a thermoresponsive middle block and hydrophobic end blocks form flower-like core-shell micelles which collapse and aggregate upon heating through the cloud point (CP). The collapse of the micellar shell and the intermicellar aggregation are followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while heating micellar solutions of a poly((styrene-d(8))-b-(N-isopropyl acrylamide)-b-(styrene-d(8))) triblock copolymer in D2O rapidly through their CP. The influence of polymer concentration as well as of the start and target temperatures is addressed. In all cases, the micellar collapse is very fast. The collapsed micelles immediately form small clusters which contain voids. They densify which slows down or even stops their growth. For low concentrations and target temperatures just above the CP, i.e. shallow temperature jumps, the subsequent growth of the clusters is described by diffusion-limited aggregation. In contrast, for higher concentrations and/or higher target temperatures, i.e. deep temperature jumps, intermicellar bridges dominate the growth. Eventually, in all cases, the clusters coagulate which results in macroscopic phase separation. For shallow temperature jumps, the cluster surfaces stay rough; whereas for deep temperature jumps, a concentration gradient develops at late stages. These results are important for the development of conditions for thermal switching in applications, e.g. for the use of thermoresponsive micellar systems for transport and delivery purposes. Y1 - 2013 U6 - https://doi.org/10.1039/c2sm27152d SN - 1744-683X VL - 9 IS - 5 SP - 1685 EP - 1699 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Dodoo, Samuel A1 - Balzer, Bizan N. A1 - Hugel, Thorsten A1 - Laschewsky, André A1 - von Klitzing, Regine T1 - Effect of ionic strength and layer number on swelling of polyelectrolyte multilayers in water vapour JF - Soft materials N2 - The swelling behavior of polyelectrolyte multilayers (PEMs) of poly(sodium-4 styrene sulfonate) (PSS) and poly(diallyl dimethyl ammonium chloride) (PDADMAC) prepared from aqueous solution of 0.1 M and 0.5 M NaCl are investigated by ellipsometry and Atomic Force Microscopy (AFM). From 1 double-layer up to 4 double-layers of 0.1 M NaCl, the amount of swelling water in the PEMs decreases with increasing number of adsorbed double layers due to an increase in polyelectrolyte density as a result of the attraction between the positively charged outermost PDADMAC layer and the Si substrate. From 6 double layers to 30 double layers, the attraction is reduced due to a much larger distance between substrate and outermost layer leading to a much lower polyelectrolyte density and higher swelling water. In PEMs prepared from aqueous solution of 0.5 M NaCl, the amount of water constantly increases which is related to a monotonically decreasing polyelectrolyte density with increasing number of polyelectrolyte layers. Studies of the surface topology also indicate a transition from a more substrate affected interphase behavior to a continuum properties of the polyelectrolyte multilayers. The threshold for the transition from interphase to continuum behavior depends on the preparation conditions of the PEM. KW - Continuum properties KW - Interphase behavior KW - Ionic strength KW - Multilayers KW - Polyelectrolytes KW - Substrate effect KW - Swelling behavior KW - Threshold KW - Water vapor Y1 - 2013 U6 - https://doi.org/10.1080/1539445X.2011.607203 SN - 1539-445X VL - 11 IS - 2 SP - 157 EP - 164 PB - Taylor & Francis Group CY - Philadelphia ER - TY - JOUR A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Rawolle, Monika A1 - Kaune, Gunar A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Müller-Buschbaum, Peter T1 - Structure and Thermal Response of Thin Thermoresponsive Polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene Films JF - Macromolecules : a publication of the American Chemical Society N2 - Thin thermoresponsive films of the triblock copolymer polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene (P(S-b-MDEGA-b-S)) are investigated on silicon substrates. By spin coating, homogeneous and smooth films are prepared for a range of film thicknesses from 6 to 82 nm. Films are stable with respect to dewetting as investigated with optical microscopy and atomic force microscopy. P(S-b-MDEGA-b-S) films with a thickness of 39 nm exhibit a phase transition of the lower critical solution temperature (LCST) type at 36.5 degrees C. The swelling and the thermoresponsive behavior of the films with respect to a sudden thermal stimulus are probed with in-situ neutron reflectivity. In undersaturated water vapor swelling proceeds without thickness increase. The thermoresponse proceeds in three steps: First, the film rejects water as the temperature is above LCST. Next, it stays constant for 600 s, before the collapsed film takes up water again. With ATR-FTIR measurements, changes of bound water in the film caused by different thermal stimuli are studied. Hydrogen bonds only form between C=O and water in the swollen film. Above the LCST most hydrogen bonds with water are broken, but some amount of bound water remains inside the film in agreement with the neutron reflectivity data. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that the inner lateral structure is not significantly influenced by the different thermal stimuli. Y1 - 2013 U6 - https://doi.org/10.1021/ma400627u SN - 0024-9297 VL - 46 IS - 10 SP - 4069 EP - 4080 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zhong, Qi A1 - Adelsberger, Joseph A1 - Niedermeier, M. A. A1 - Golosova, Anastasi A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Funari, S. S. A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter T1 - The influence of selective solvents on the transition behavior of poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) thick films JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - Thick poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) [P(S-b-MDEGA-b-S)] films (thickness 5 mu m) are prepared from different solvents on flexible substrates by solution casting and investigated with small-angle X-ray scattering. As the solvents are either PS- or PMDEGA-selective, micelles with different core-shell micellar structures are formed. In PMDEGA-selective solvents, the PS block is the core and PMDEGA is the shell, whereas in PS-selective solvents, the order is reversed. After exposing the films to liquid D2O, the micellar structure inside the films prepared from PMDEGA-selective solvents remains unchanged and only the PMDEGA (shell part) swells. On the contrary, in the films prepared from PS-selective solvents, the micelles revert the core and the shell. This reversal causes more entanglements of the PMDEGA chains between the micelles. Moreover, the thermal collapse transition of the PMDEGA block in liquid D2O is significantly broadened. Irrespective of the solvent used for film preparation, the swollen PMDEGA shell does not show a prominent shrinkage when passing the phase transition, and the transition process occurs via compaction. The collapsed micelles have a tendency to densely pack above the transition temperature. KW - Hydrogel KW - Thin film KW - Thermo-responsive KW - LCST behavior KW - SAXS Y1 - 2013 U6 - https://doi.org/10.1007/s00396-012-2879-4 SN - 0303-402X VL - 291 IS - 6 SP - 1439 EP - 1451 PB - Springer CY - New York ER - TY - JOUR A1 - Miasnikova, Anna A1 - Benitez-Montoya, Carlos Adrian A1 - Laschewsky, André T1 - Counterintuitive photomodulation of the thermal phase transition of poly(methoxy diethylene glycol acrylate) in aqueous solution by trans-cis isomerization of Copolymerized Azobenzenes JF - Macromolecular chemistry and physics N2 - The non-ionic monomer (methoxy diethylene glycol) acrylate is copolymerized with its azodye-functionalized acrylate analogue using reversible addition-fragmentation chain transfer (RAFT) polymerization. Copolymerization is increasingly difficult with increasing amounts of the azo-dye-bearing monomer. The resulting water-soluble polymers are thermosensitive, exhibiting lower critical solution temperature (LCST) behavior, which can be modulated by the photoinduced trans-cis isomerization of the dye. While already small contents of the hydrophobic azobenzene group reduce the phase-transition temperatures of the copolymers strongly, photoisomerization of the apolar trans-state to the more-polar cis-state has only a small effect, and decreases rather than increases the cloud points. KW - azobenzene KW - photoisomerization KW - statistical copolymers KW - thermoresponsive materials KW - water-soluble polymers Y1 - 2013 U6 - https://doi.org/10.1002/macp.201300203 SN - 1022-1352 VL - 214 IS - 13 SP - 1504 EP - 1514 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Marsat, Jean-Noel A1 - Stahlhut, Frank A1 - Laschewsky, André A1 - von Berlepsch, Hans A1 - Böttcher, Christoph T1 - Multicompartment micelles from silicone-based triphilic block copolymers JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - An amphiphilic linear ternary block copolymer was synthesised in three consecutive steps via reversible addition-fragmentation chain transfer polymerisation. Oligo(ethylene glycol) monomethyl ether acrylate was engaged as a hydrophilic building block, while benzyl acrylate and 3-tris(trimethylsiloxy)silyl propyl acrylate served as hydrophobic building blocks. The resulting "triphilic" copolymer consists thus of a hydrophilic (A) and two mutually incompatible "soft" hydrophobic blocks, namely, a lipophilic (B) and a silicone-based (C) block, with all blocks having glass transition temperatures well below 0 A degrees C. The triphilic copolymer self-assembles into spherical multicompartment micellar aggregates in aqueous solution, where the two hydrophobic blocks undergo local phase separation into various ultrastructures as evidenced by cryogenic transmission electron microscopy. Thus, a silicone-based polymer block can replace the hitherto typically employed fluorocarbon-based hydrophobic blocks in triphilic block copolymers for inducing multicompartmentalisation. KW - Amphiphiles KW - Triphilic block copolymers KW - Core-shell-corona micelles KW - RAFT KW - Cryo-TEM KW - Multicompartment micelles Y1 - 2013 U6 - https://doi.org/10.1007/s00396-013-3001-2 SN - 0303-402X SN - 1435-1536 VL - 291 IS - 11 SP - 2561 EP - 2567 PB - Springer CY - New York ER - TY - JOUR A1 - Inal, Sahika A1 - Kölsch, Jonas D. A1 - Chiappisi, Leonardo A1 - Janietz, Dietmar A1 - Gradzielski, Michael A1 - Laschewsky, André A1 - Neher, Dieter T1 - Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers N2 - We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore. Y1 - 2013 UR - http://pubs.rsc.org/en/content/articlepdf/2013/tc/c3tc31304b U6 - https://doi.org/10.1039/C3TC31304B ER - TY - JOUR A1 - Inal, Sahika A1 - Kölsch, Jonas D. A1 - Selrie, Frank A1 - Schenk, Jörg A. A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Neher, Dieter T1 - A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein N2 - We present two thermoresponsive water soluble copolymers prepared via free radical statistical copolymerization of N-isopropylacrylamide (NIPAm) and of oligo(ethylene glycol) methacrylates (OEGMAs), respectively, with a solvatochromic 7-(diethylamino)-3-carboxy-coumarin (DEAC)-functionalized monomer. In aqueous solutions, the NIPAm-based copolymer exhibits characteristic changes in its fluorescence profile in response to a change in solution temperature as well as to the presence of a specific protein, namely an anti-DEAC antibody. This polymer emits only weakly at low temperatures, but exhibits a marked fluorescence enhancement accompanied by a change in its emission colour when heated above its cloud point. Such drastic changes in the fluorescence and absorbance spectra are observed also upon injection of the anti-DEAC antibody, attributed to the specific binding of the antibody to DEAC moieties. Importantly, protein binding occurs exclusively when the polymer is in the well hydrated state below the cloud point, enabling a temperature control on the molecular recognition event. On the other hand, heating of the polymer-antibody complexes releases a fraction of the bound antibody. In the presence of the DEAC-functionalized monomer in this mixture, the released antibody competitively binds to the monomer and the antibody-free chains of the polymer undergo a more effective collapse and inter-aggregation. In contrast, the emission properties of the OEGMA-based analogous copolymer are rather insensitive to the thermally induced phase transition or to antibody binding. These opposite behaviours underline the need for a carefully tailored molecular design of responsive polymers aimed at specific applications, such as biosensing. Y1 - 2013 UR - http://pubs.rsc.org/en/content/articlepdf/2013/tb/c3tb21245a U6 - https://doi.org/10.1039/c3tb21245a ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Marsat, Jean-Noël A1 - Heydenreich, Matthias A1 - von Berlepsch, Hans A1 - Laschewsky, André T1 - Self-Assembly into Multicompartment Micelles and Selective Solubilization by Hydrophilic-Lipophilic- Fluorophilic Block Copolymers Y1 - 2011 SN - 0024-9297 ER - TY - JOUR A1 - Strehmel, Veronika A1 - Laschewsky, André A1 - Stoesser, Reinhard A1 - Zehl, Andrea A1 - Herrmann, Werner T1 - Mobility of spin probes in ionic liquids N2 - The spin probes TEMPO, TEMPOL, and CAT-1 were used to investigate microviscosity and micropolarity of imidazolium based ionic liquids bearing either tetrafluoroborate or hexafluorophosphate as anions and a variation of the substitution at the imidazolium ion. The average rotational correlation times (r) obtained by complete simulation of the X-band ESR spectra of TEMPO, TEMPOL, and CAT-1 increase with increasing viscosity of the ionic liquid although no Stokes Einstein behavior is observed. This is caused by microviscosity effects of the ionic liquids shown by application of the Gierer-Wirtz theory. Interestingly, the jump of the probe molecule into the free volume of the ionic liquids is a nonactivated process. The hyperfine coupling constants (A(iso) (N-14)) of TEMPO and TEMPOL dissolved in the ionic liquids do not depend on the structure of the ionic liquids. The A(iso) (N-14) values show a micropolarity of the ionic liquids that is comparable with methylenchloride in case of TEMPO and with dimethylsulfoxide in case of TEMPOL. Micropolarity monitored by CAT-1 strongly depends on structural variation of the ionic liquid. CAT-1 dissolved in imidazolium salts substituted with shorter alkyl chains at the nitrogen atom exhibits a micropolarity comparable with dimethylsulfoxide. A significant lower micropolarity is found for imidazolium. salts bearing a longer alkyl substituent at the nitrogen atom or a methyl substituent at C-2. Copyright (c) 2006 John Wiley & Sons, Ltd Y1 - 2006 UR - http://onlinelibrary.wiley.com/doi/10.1002/poc.1072/pdf U6 - https://doi.org/10.1002/poc.1072 ER - TY - JOUR A1 - Rullens, F A1 - Vuillaume, Pascal Y. A1 - Moussa, Alain A1 - Habib-Jiwan, Jean-Louis A1 - Laschewsky, André T1 - Ordered polyelectrolyte "Multilayers". 7. Hybrid films self-assembled from fluorescent and smectogenic poly(diallylammonium) salts and delaminated clay N2 - Homopolymers were prepared from diallylammonium monomers bearing 4-methylcoumarin and 4-cyanobiphenyl as fluorescent and mesogenic side groups, as well as their copolymers with diallyldimethylammonium chloride (DADMAC). Organic-inorganic hybrid films were electrostatically self-assembled via the layer-by-layer technique on silicon wafers and quartz plates from the chromophore-bearing polymers and an exfoliated synthetic hectorite. Photophysical studies performed in solution as well as in the self-assembled films demonstrated only a weak tendency for aggregation of the chromophores in the macromolecules. Moreover, assemblies made from the polymers carrying the cyanobiphenyl mesogen were found to exhibit a pronounced internal order Y1 - 2006 UR - http://pubs.acs.org/doi/full/10.1021/cm060209x U6 - https://doi.org/10.1021/Cm060209x ER - TY - JOUR A1 - Rullens, F A1 - Laschewsky, André A1 - Devillers, M T1 - Bulk and thin films of bismuth vanadates prepared from hybrid materials made from an organic polymer and inorganic salts N2 - A new precursor route for the preparation of bulk oxides and thin films of bismuth vanadates is proposed. The method involves the thermal treatment under air and mild conditions of hybrid organic-inorganic precursors, made from a zwitterionic salt-free polymer matrix and selected inorganic species. Monoclinic BiVO4 was obtained in the form of bulk oxide by calcination of the powdered homogeneous hybrid materials at 600 degrees C, from precursors containing Bi and V in stoichiometric amounts. In the same way, thermodiffractometry studies performed on a hybrid material exhibiting a Bi/ V molar ratio of 2 revealed that the ionic conductor gamma-Bi4V2O11 phase can be stabilized under very soft thermal conditions (300 degrees C). Additionally, thin films of yellow monoclinic BiVO4 were for the first time fabricated, by thermal treatment of the same hybrid polymeric precursors deposited on quartz substrates by spin coating, using a layer- by-layer technique. The presence of the target phase at the surface of the plates was confirmed by X-ray diffraction as well as UV-vis measurements Y1 - 2006 UR - http://pubs.acs.org/doi/full/10.1021/cm051516q U6 - https://doi.org/10.1021/Cm051516q ER - TY - JOUR A1 - Harms, Stephan A1 - Raetzke, Klaus A1 - Faupel, Franz A1 - Egger, Werner A1 - Ravello, Lori Boyd de A1 - Laschewsky, André A1 - Wang, Weinan A1 - Müller-Buschbaum, Peter T1 - Free volume and swelling in thin films of poly(n-isopropylacrylamide) end-capped with n-butyltrithiocarbonate N2 - The free volume in thin films of poly(N-isopropylacrylamid) end-capped with n-butyltrio-carbonate (nbc-PNIPAM) is probed with positron annihilation lifetime spectroscopy (PALS). The PALS measurements are performed as function of energy to obtain depth profiles of the free volume of nbc-PNIPAM films. The range of nbc-PNIPAM films with thicknesses from 40 to 200 nm is focused. With decreasing film thickness the free volume increases in good agreement with an increase in the maximum swelling capability of the nbc-PNIPAM films. Thus in thin hydrogel films the sorption and swelling behavior is governed by free volume. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/10003270 U6 - https://doi.org/10.1002/marc.201000067 SN - 1022-1336 ER - TY - JOUR A1 - Glatzel, Stefan A1 - Badi, Nezha A1 - Paech, Michael A1 - Laschewsky, André A1 - Lutz, Jean-Francois T1 - Well-defined synthetic polymers with a protein-like gelation behavior in water N2 - Homopolymers of N-acryloyl glycinamide were prepared by reversible addition-fragmentation chain transfer polymerization in water. The formed macromolecules exhibit strong polymer-polymer interactions in aqueous milieu and therefore form thermoreversible physical hydrogels in pure water, physiological buffer or cell medium. Y1 - 2010 UR - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CC U6 - https://doi.org/10.1039/C0cc00038h SN - 1359-7345 ER - TY - JOUR A1 - Fandrich, Nick A1 - Falkenhagen, Jana A1 - Weidner, Steffen M. A1 - Staal, Bastiaan A1 - Thuenemann, Andreas F. A1 - Laschewsky, André T1 - Characterization of new amphiphilic block copolymers of N-vinylpyrrolidone and vinyl acetate, 2-chromatographic separation and analysis by MALDI-TOF and FT-IR coupling N2 - PVP-block-PVAc block copolymers were synthesized by controlled radical polymerization applying a RAFT/MADIX system and were investigated by HPLC and by coupling of chromatography to FT-IR spectroscopy and MALDI-TOF MS. Chromatographic methods (LACCC and gradient techniques) were developed that allowed a separation of block copolymers according to their repeating units. The results of the spectroscopic and spectrometric analysis clearly showed transfer between radicals and process solvent. With the use of hyphenated techniques differences between main and side products were detected. In agreement with previously published results, obtained by NMR, SEC, static light scattering and MALDI- TOF MS, our data proved a non-ideal RAFT polymerization. Y1 - 2010 UR - http://www3.interscience.wiley.com/journal/10003495/home U6 - https://doi.org/10.1002/macp.201000044 SN - 1022-1352 ER - TY - JOUR A1 - Fandrich, Nick A1 - Falkenhagen, Jana A1 - Weidner, Steffen M. A1 - Pfeifer, Dietmar A1 - Staal, Bastiaan A1 - Thuenemann, Andreas F. A1 - Laschewsky, André T1 - Characterization of new amphiphilic block copolymers of N-vinyl pyrrolidone and vinyl acetate, 1-analysis of copolymer composition, end groups, molar masses and molar mass distributions N2 - New amphiphilic block copolymers consisting of N-vinyl pyrrolidone and vinyl acetate were synthesized via controlled radical polymerization using a reversible addition/fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) system. The synthesis was carried out in 1,4-dioxane as process solvent. In order to get conclusions on the mechanism of the polymerization the molecular structure of formed copolymers was analysed by means of different analytical techniques. C-13 NMR spectroscopy was used for the determination of the monomer ratios. End groups were analysed by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This technique was also used to determine possible fragmentations of the RAFT end groups. By means of a combination of size exclusion chromatography, C-13 NMR and static light scattering molar mass distributions and absolute molar masses could be analysed. The results clearly show a non-ideal RAFT mechanism. Y1 - 2010 UR - http://www3.interscience.wiley.com/journal/10003495/home U6 - https://doi.org/10.1002/macp.200900466 SN - 1022-1352 ER - TY - JOUR A1 - Bivigou Koumba, Achille Mayelle A1 - Goernitz, Eckhard A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Thermoresponsive amphiphilic symmetrical triblock copolymers with a hydrophilic middle block made of poly(N- isopropylacrylamide) : synthesis, self-organization, and hydrogel formation N2 - Several series of symmetrical triblock copolymers were synthesized by the reversible addition fragmentation chain transfer method. They consist of a long block of poly(N-isopropylacrylamide) as hydrophilic, thermoresponsive middle block, which is end-capped by two small strongly hydrophobic blocks made from five different vinyl polymers. The association of the amphiphilic polymers was studied in dilute and concentrated aqueous solution. The polymer micelles found at low concentrations form hydrogels at high concentrations, typically above 30-35 wt.%. Hydrogel formation and the thermosensitive rheological behavior were studied exemplarily for copolymers with hydrophobic blocks of polystyrene, poly(2-ethylhexyl acrylate), and poly(n-octadecyl acrylate). All systems exhibited a cloud point around 30 A degrees C. Heating beyond the cloud point initially favors hydrogel formation but continued heating results in macroscopic phase separation. The rheological behavior suggests that the copolymers associate into flower-like micelles, with only a small share of polymers that bridge the micelles and act as physical cross-linkers, even at high concentrations. Y1 - 2010 UR - http://www.springerlink.com/content/101551 U6 - https://doi.org/10.1007/s00396-009-2179-9 SN - 0303-402X ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Kulkarni, Amit A1 - Jain, Abhinav A1 - Wang, Weinan A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Pipich, Vitaliy A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Thermoresponsive PS-b-PNIPAM-b-PS micelles : aggregation behavior, segmental dynamics, and thermal response N2 - We have studied I lie thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylarnicle) (PNIPAM) middle block exhibiting a lower critical solution temperature (LCST) in aqueous solution. A wide range of concentrations (0.1-300 mg/mL) is investigated using it number of analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and neutron spin-echo spectroscopy (NSE). The critical micelle concentration is determined using FCS to be 1 mu M or less. The collapse of the micelles at the LCST is investigated using turbidimetry and DLS and shows a weak dependence on the degree of polymerization of the PNIPAM block. SANS with contrast matching allows its to reveal the core-shell Structure of the micelles as well as their correlation as a function of temperature. The segmental dynamics of the PNIPAM shell are studied as a function of temperature and arc found to be faster in the collapsed state than in the swollen state. The mode detected has a linear dispersion in q(2) and is found to be faster in the collapsed state as compared to the swollen state. We attribute this result to the averaging over mobile and immobilized segments. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma902714p SN - 0024-9297 ER - TY - JOUR A1 - Wischerhoff, Erik A1 - Glatzel, Stefan A1 - Uhlig, Katja A1 - Lankenau, Andreas A1 - Lutz, Jean-Francois A1 - Laschewsky, André T1 - Tuning the thickness of polymer brushes grafted from nonlinearly growing multilayer assemblies N2 - A new versatile method for tuning the thickness of surface-tethered polymer brushes is introduced. It is based on the combination of polyelectrolyte multilayer deposition and surface-initiated atom transfer radical polymerization. To control the thickness of the brushes, the nonlinear growth of certain polyelectrolyte multilayer systems is exploited. The method is demonstrated to work with different polyelectrolytes and different monomers. The relevance for applications is demonstrated by cell adhesion experiments oil grafted thermoresponsive polymer layers with varying thickness. Y1 - 2009 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La804197j SN - 0743-7463 ER - TY - JOUR A1 - von Berlepsch, Hans A1 - Boettcher, Christoph A1 - Skrabania, Katja A1 - Laschewsky, André T1 - Complex domain architecture of multicompartment micelles from a linear ABC triblock copolymer revealed by cryogenic electron tomography N2 - Cryo-electron tomography of raspberry-like multicompartment micelles formed by a linear ABC triblock copolymer in water revealed that the fluorocarbon domains may be dispersed all over the hydrocarbon core. Y1 - 2009 UR - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CC U6 - https://doi.org/10.1039/B903658j SN - 1359-7345 ER - TY - JOUR A1 - Skrabania, Katja A1 - Laschewsky, André A1 - von Berlepsch, Hans A1 - Boettcher, Christoph T1 - Synthesis and micellar self-assembly of ternary hydrophilic-lipophilic-fluorophilic block copolymers with a linear PEO chain N2 - Linear amphiphilic diblock and ternary triblock copolymers were synthesized by the RAFT method in two successive steps using a poly(ethylene oxide) (PEO) macrochain transfer agent, butyl or 2-ethylhexyl acrylate, and 1H, 1H, 2H, 2H-perfluorodecyl acrylate. The diblock and the triblock copolymers, which consist of a hydrophilic, a lipophilic, and a short fluorophilic block, self-assemble in water into spherical micellar aggregates. Imaging by cryogenic transmission electron microscopy (cryo-TEM) revealed that the micellar cores of the aggregates made from these "triphilic" copolymers can undergo local phase separation to form a unique ultrastructure. In these multicompartment micelles, it appears that extended nonspherical domains, presumably made of nanocrystallites of the fluorocarbon block, are embedded in the hydrocarbon matrix forming the spherical micellar core. This novel internal structure of a micellar core is attributed to the mutual incompatibility of the fluorocarbon and hydrocarbon side chains in combination with the tendency of the used fluorocarbon acrylate monomer to undergo side-chain crystallization. Y1 - 2009 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La900253j SN - 0743-7463 ER - TY - JOUR A1 - Köhler, Ralf A1 - Doench, Ingo A1 - Ott, Patrick A1 - Laschewsky, André A1 - Fery, Andreas A1 - Krastev, Rumen T1 - Neutron reflectometry study of swelling of polyelectrolyte multilayers in water vapors : influence of charge density of the polycation N2 - We studied the swelling of polyelectrolyte (PE) multilayers (PEM) in water (H2O) vapors. The PEM were made from polyanion poly(styrene sulfonate) (PSS) and polycation poly(diallyldimethylammonium chloride)-N-methyl-N-vinylacetamide (pDADMAC-NMVA). While PSS is a fully charged polyanion, pDADMAC-NMVA is a random copolymer made of charged pDADMAC and uncharged NMVA monomer units. Variation of the relative amount of these two units allows for controlling the charge density of pDADMAC-NMVA. The degree of swelling was studied as it function of the relative humidity in the experimental chamber (respectively water concentration in the gas phase) for PEM prepared from PSS and pDADMAC-NMVA with their different charge densities - 100%, 89% and 75%. The films were prepared by means of spraying technique and consisted of six PE couples-PSS/pDADMAC-NMVA. Neutron reflectometry was applied as main tool to observe the swelling process. The technique allows to obtain in a single experiment information about film thickness and amount of water in the film. The experiments were complemented with AFM measurements to obtain the thickness of the films. It was found that the Film thickness increases when the charge density of the polycation decreases. The swelling of the PEM increases with the relative humidity and it depends on the charge density of pDADMAC-NMVA. The swelling behavior is 2-fold, splitting up in a charge dependent mode with relatively little volume increase, and a second mode With high volume expansion, which is independent from charge density of PEM. The "swelling transition" occurs for all samples at a relative humidity about 60% and a volume increase of ca. 20%. The results were interpreted according to the Flory-Huggins theory which assumes a phase separation in PEM network at higher water contents. Y1 - 2009 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La901508w SN - 0743-7463 ER - TY - JOUR A1 - Bivigou Koumba, Achille Mayelle A1 - Kristen, Juliane A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Synthesis of symmetrical triblock copolymers of styrene and N-isopropylacrylamide using bifunctional bis(trithiocarbonate)s as RAFT agents N2 - Six new bifunctional bis(trithiocarbonate)s were explored as RAFT agents for synthesizing amphiphilic triblock copolymers ABA and BAB, with hydrophilic "A" blocks made from N-isopropylacrylamide and hydrophobic "B" blocks made from styrene. Whereas the extension of poly(N-isopropylacrylamide) by styrene was not effective, polystyrene macroRAFT agents provided the block copolymers efficiently. End group analysis by H-1 NMR spectroscopy supported molar mass analysis and revealed an unexpected side reaction for certain bis(trithiocarbonate)s, namely a fragmentation to simple trithiocarbonates while extruding ethylene-trithiocarbonate. The amphiphilic block copolymers with short polystyrene blocks are directly soluble in water and self-organize into thermo-responsive micellar aggregates. Y1 - 2009 UR - http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291521-3935 U6 - https://doi.org/10.1002/macp.200800575 SN - 1022-1352 ER - TY - JOUR A1 - Wang, Weijia A1 - Kaune, Gunar A1 - Perlich, Jan A1 - Paradakis, Christine M. A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Schlage, K. A1 - Röhlsberger, Ralf A1 - Roth, Stephan V. A1 - Cubitt, Robert A1 - Müller-Buschbaum, Peter T1 - Swelling and switching kinetics of gold coated end-capped poly(N-isopropylacrylamide) thin films N2 - Thin thermoresponsive hydrogel films of poly(N-isopropylacrylamide) end-capped with n-butyltrithiocarbonate(nbc- PNIPAM) oil si I icon supports with a gold layer on top, causing an asymmetric confinement, are investigated. For two different gold layer thicknesses (nominally 0.4 and 5 rim), the swelling and switching kinetics are probed with in situ neutron reflectivity. With a temperature jump from 23 to 40 degrees C the film is switched from a swollen into a collapsed state. For the thin gold layer this switching is faster as compared to the thick gold layer. The switching is a two-step process of water release and a subsequent structural relaxation. fit swelling and deswelling cycles, aging of the films is probed. After five cycles, the film exhibits enhanced water storage capacity. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that these gold coated nbc-PNIPAM films do not age with respect to the inner structure but slightly roughen at the gold surface. As revealed by atomic force microscopy, the morphology of the gold layer is changed by the water uptake and release. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma902637a SN - 0024-9297 ER - TY - JOUR A1 - Uhlig, Katja A1 - Wischerhoff, Erik A1 - Lutz, Jean-Francois A1 - Laschewsky, André A1 - Jäger, Magnus S. A1 - Lankenau, Andreas A1 - Duschl, Claus T1 - Monitoring cell detachment on PEG-based thermoresponsive surfaces using TIRF microscopy N2 - Recently, we introduced a thermoresponsive copolymer that consists of oligo(ethylene glycol) methacrylate (OEGMA) and 2-(2- methoxyethoxy) ethyl methacrylate (MEO(2)MA). The polymer exhibited an LCST at 35 degrees C in PBS buffer and was anchored onto gold substrates using disulfide polymerisation initiators. It allows the noninvasive detachment of adherent cells from their substrate. As the mechanisms that determine the interaction of cells with such polymers are not well understood, we employed Total Internal Reflection Fluorescence (TIRF) microscopy in order to monitor the detachment process of cells of two different types. We identified contact area and average cell-substrate distance as crucial parameters for the evaluation of the detachment process. The sensitivity of TIRF microscopy allowed us to correlate the specific adhesion pattern of MCF-7 breast cancer cells with the morphology of cell deposits that may serve as fingerprints for a nondestructive characterisation of live cells. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/sm/index.asp U6 - https://doi.org/10.1039/C0sm00010h SN - 1744-683X ER - TY - JOUR A1 - Skrabania, Katja A1 - von Berlepsch, Hans A1 - Böttcher, Christoph A1 - Laschewsky, André T1 - Synthesis of ternary, hydrophilic-lipophilic-fluorophilic block copolymers by consecutive RAFT polymerizations and their self-assembly into multicompartment micelles N2 - Linear amphiphilic diblock and ternary triblock copolymers were synthesized by the RAFT method in three Successive Steps, using oligo(ethylene oxide) monomethyl ether acrylate, butyl or 2-ethylhexyl acrylate, and 1H, 1H, 2H, 2H-perfluorodecyl acrylate. The diblock and the triblock copolymers, which consist of a hydrophilic, a lipophilic, and a fluorophilic block, self-assemble in water into spherical micellar aggregates. Imaging by cryogenic transmission electron microscopy (cryo-TEM) revealed that the cores of the micellar aggregates made from these "triphilic" copolymers undergo local phase separation to form various ultrastructures, which depend sensitivity on the given block sequence. While the sequence hydrophilic-lipophilic-fluorophilic resulted in multicompartment cores with core-shell-corona morphology, the sequence lipophilic-hydrophilic-fluorophilic provided new "patched double micelle" and larger "soccer ball" structures. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma901913f SN - 0024-9297 ER - TY - JOUR A1 - Zehm, Daniel A1 - Laschewsky, André A1 - Gradzielski, Michael A1 - Prévost, Sylvain A1 - Liang, Hua A1 - Rabe, Jürgen P. A1 - Schweins, Ralf A1 - Gummel, Jérémie T1 - Amphiphilic dual brush block copolymers as "giant surfactants" and their aqueous self-assembly N2 - Amphiphilic dual brush diblock as well as symmetrical triblock polymers were synthesized by the overlay of the reversible addition-fragmentation chain transfer and the nitroxide mediated polymerization (NMP) techniques. While poly(ethylene glycol) brushes served as hydrophilic block, the hydrophobic block was made of polystyrene brushes. The resulting "giant surfactants" correspond structurally to the established amphiphilic diblock and triblock copolymer known as macrosurfactants. The aggregation behavior of the novel "giant surfactants" in aqueous solution was studied by dynamic light scattering, small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) over a large range in reciprocal space. Further, the self-assembled aggregates Were investigated by scanning force microscopy (SFM) after deposition on differently functionalized ultraflat solid substrates. Despite the high fraction of hydrophobic segments, the polymers form stable mesoscopic, spherical aggregates with hydrodynamic diameters in the range of 150-350 nm. Though prepared from well-defined individual polymers, the aggregates show several similarities to hard core latexes. They are stable enough to he deposited without much changes onto surfaces, where they cluster and show Spontaneous sorting according to their size within the clusters, with the larger aggregates being in the center. Y1 - 2010 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La903087p SN - 0743-7463 ER - TY - JOUR A1 - Wischerhoff, Erik A1 - Badi, Nezha A1 - Lutz, Jean-Francois A1 - Laschewsky, André T1 - Smart bioactive surfaces N2 - The purpose of this highlight is to define the emerging field of bioactive surfaces. In recent years, various types of synthetic materials capable of "communicating'' with biological objects such as nucleic acids, proteins, polysaccharides, viruses, bacteria or living cells have been described in the literature. This novel area of research certainly goes beyond the traditional field of smart materials and includes different types of sophisticated interactions with biological entities, such as reversible adhesion, conformational control, biologically-triggered release and selective permeation. These novel materials may be 2D planar surfaces as well as colloidal objects or 3D scaffolds. Overall, they show great promise for numerous applications in biosciences and biotechnology. For instance, practical applications of bioactive surfaces in the fields of bioseparation, cell engineering, biochips and stem-cell differentiation are briefly discussed herein. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/sm/index.asp U6 - https://doi.org/10.1039/B913594d SN - 1744-683X ER - TY - JOUR A1 - Wattebled, Laurent A1 - Laschewsky, André A1 - Moussa, Alain A1 - Habib-Jiwan, Jean-Louis T1 - Aggregation numbers of cationic oligomeric surfactants : A time-resolved fluorescence quenching study N2 - The micelle aggregation numbers (N-agg) of several series of cationic oligomeric surfactants were determined by time-resolved fluorescence quenching (TRFQ) experiments, using advantageously 9,10-dimethylanthracene as fluorophore. The study comprises six dimeric ("gemini"), three trimeric, and two tetrameric surfactants, which are quaternary ammonium chlorides, with medium length spacer groups (C-3-C-6) separating the individual surfactant fragments. Two standard cationic surfactants served as references. The number of hydrophobic chains making up a micellar core is relatively low for the oligomeric surfactants, the spacer length playing an important role. For the dimers, the number decreases from 32 to 21 with increasing spacer length. These numbers decrease further with increasing degree of oligomerization down to values of about 15. As for many conventional ionic surfactants, the micelles of all oligomers studied grow only slightly with the concentration, and they remain in the regime of small micelles up to concentrations of at least 3 wt %. Y1 - 2006 UR - http://pubs.acs.org/doi/full/10.1021/la052414h U6 - https://doi.org/10.1021/La052414h ER - TY - JOUR A1 - Laschewsky, André A1 - Kirsten, Juliane A1 - Skrabania, Katja A1 - Storsberg, Joachim T1 - Designing functional macrosurfactants via triblock tercopolymers Y1 - 2006 SN - 0065-7727 ER - TY - JOUR A1 - Strehmel, Veronika A1 - Laschewsky, André A1 - Wetzel, Hendrik A1 - Gornitz, Eckhard T1 - Free radical polymerization of n-butyl methacrylate in ionic liquids N2 - Ionic liquids based on imidazolium, pyridinium, and alkylammonium salts were investigated as solvents in free radical polymerization of the model monomer n-butyl methacrylate. The properties of the ionic liquids were systematically varied by changing the length of the alkyl substituents on the cations, and by employing different anions such as tetrafluoroborate, hexafluorophosphate, tosylate, triflate, alkyl sulfates and dimethyl phosphate. Results were compared to analogous polymerizations in toluene and in bulk. The solvents have no detectable influence on polymer tacticity. However, the molar masses obtained and the degree of polymerization, respectively, are very sensitive to the choice of the solvent. The degrees of polymerization are significantly higher when polymerizations were carried out in ionic liquids compared to polymerization in toluene, and can even exceed the values obtained by bulk polymerization. Imidazolium salts unsubstituted at C-2 result in an increase in the degree of polymerization of the poly(butyl methacrylate) with increasing viscosity of these ionic liquids. Methyl substitution at C-2 of the imidazolium ion results in an increase in the viscosity of the ionic liquid and in a viscosity independent degree of polymerization of the poly(butyl methacrylate). Ionic liquids based on imidazolium salts seem preferable over pyridinium and alkylammonium salts because of the higher degree of polymerization of the poly(butyl methacrylate)s obtained in the imidazolium salts. The glass transition temperatures and thermal stabilities are higher for poly(butyl methacrylate)s synthesized in the ionic liquids compared to the polymer made in toluene Y1 - 2006 UR - http://pubs.acs.org/doi/full/10.1021/ma0516945 U6 - https://doi.org/10.1021/Ma0516945 ER - TY - JOUR A1 - Strehmel, Veronika A1 - Kraudelt, Heide A1 - Wetzel, Hendrik A1 - Görnitz, Eckhard A1 - Laschewsky, André T1 - Free radical polymerization of methacrylates in ionic liquids Y1 - 2004 ER - TY - JOUR A1 - Koetse, Marc M. A1 - Laschewsky, André A1 - Jonas, Alain M. A1 - Verbiest, T. T1 - Orientation of functional groups in polyelectrolyte multilayers studied by second-harmonic generation (SHG) Y1 - 2002 SN - 0927-7757 ER - TY - JOUR A1 - Mangeney, Claire A1 - Ferrage, Fabien A1 - Jullien, Ludovic A1 - Ouari, Olivier A1 - Rékaï, El-Djouhar A1 - Laschewsky, André A1 - Vikholm, Inger A1 - Sadowski, Janusz W. T1 - Synthesis and properties of water-soluble gold colloids covalently derivatized with neutral polymer monolayers N2 - Citrate-capped gold nanoparticles as well as planar gold surfaces can be efficiently grafted with a covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surface with dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shown by UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies. The hydrophilic polymer-coated gold colloids can be freeze-dried and stored as powders that can be subsequently dissolved to yield stable aqueous dispersions, even at very large concentrations. They allow for applying filtrations, gel permeation chromatography, or centrifugation. They do not suffer from undesirable nonspecific adsorption of proteins while allowing the diffusion of small species within the hydrogel surface coating. In addition, specific properties of the original hydrophilic polymers are retained such as a lower critical solution temperature. The latter feature could be useful to enhance optical responses of functionalized gold surfaces toward interaction with various substrates. Y1 - 2002 ER - TY - JOUR A1 - Glinel, Karine A1 - Moussa, Alain A1 - Jonas, Alain M. A1 - Laschewsky, André T1 - The influence of polyelectrolyte charge density on the formation of multilayers of strong polyelectrolytes at low ionic strength N2 - The influence of the charge density of polyelectrolytes on the growth of polyelectrolyte multilayers via layer- by-layer self-assembly from pure aqueous solutions was studied. Multilayers were built from strong polyanions, namely poly(styrenesulfonate) and an exfoliated synthetic hectorite, and cationic copolymers of diallyldimethylammonium chloride (DADMAC) with N-methyl-N-vinylformamide (NMVF) for which the composition and thus the charge density was varied systematically. The analysis of the system {cationic copolymer/poly(styrenesulfonate)} reveals that a critical linear charge density Ïc of 0.036 elementary charge/Å of contour length is necessary to obtain stable multilayer growth in pure water. Above Ïc, the increment of thickness/deposition cycle varies with the linear charge density of the cationic copolymers, in good agreement with current theories of polyelectrolyte solutions. As linear charge density increases, the system passes successively through a charge-dependent ?Debye-Hu ckel? regime and then through a chargeindependent ?strong-screening? regime where counterion condensation dominates the behavior. Analogous results were obtained for the variation of the basal spacing of internally structured hybrid multilayers {cationic copolymer/hectorite}. However, by contrast with the first system, no critical linear charge density was found for the hybrid system. This is explained by additional, nonelectrostatic interactions between the clay platelets and the formamide fragment. Y1 - 2002 ER - TY - JOUR A1 - Kotzev, Anton A1 - Laschewsky, André A1 - Adriaensens, Pieter A1 - Gelan, Jan T1 - Micellar Polymers with Hydrocarbon and Fluorocarbon Hydrophobic Chains : a Strategy to Multicompartment Micelles N2 - Cationic ionenes bearing hydrophobic side chains were synthesized, which behave as micellar polymers of the polysoap type. The hydrophobic chains were either hydrocarbons or fluorocarbons, or a mixture of both, in the form of statistical as well as block copolymers. These amphiphilic polymers were studied and compared with each other and with low molar mass analogous surfactants, especially with respect to their hydrophobic association in aqueous solution. The particular molecular structure of the ionenes synthesized results in polymeric surfactants with high mobility of the fluorocarbon chains. Most noteworthy, the behavior of the hydrocarbon-fluorocarbon block copolymer soaps in aqueous solution indicates microphase separation into hydrocarbon-rich and fluorocarbon-rich hydrophobic domains, thus yielding multicompartment micelles. Y1 - 2002 ER - TY - JOUR A1 - Glinel, Karine A1 - Laschewsky, André A1 - Jonas, Alain M. T1 - Ordered polyelectrolyte "multilayers" : 4. internal structure of clay-based multilayers N2 - We report on the growth and structure of hybrid clay-based multilayers obtained by electrostatic self-assembly (also known as layer-by-layer assembly) of poly(diallylpyrrolidinium bromide) and a synthetic hectorite (Laponite). By combining ellipsometry, atomic force microscopy, and specular and off-specular grazing angle X-ray scattering measurements, we show that platelets pack in the vertical direction according to a distribution of distances between nearest neighbors of about 3 Å standard deviation. The accumulation of such random fluctuations in the vertical direction results in the loss of layering of the platelets farther than about 75 Å from the substrate. In this respect, most of the film should be considered as a nanocomposite with preferential orientation of the platelets, rather than as a real multilayer. The model is quantitatively supported by simulations of the specular and off-specular scattering of such multilayers. Y1 - 2002 ER - TY - JOUR A1 - Vuillaume, Pascal Y. A1 - Jonas, Alain M. A1 - Laschewsky, André T1 - Ordered polyelectrolyte "multilayers" : 5. photo-cross-linking of hybrid films containing a new unsaturated and hydrophobized poly(diallylammonium) salt and exfoliated clay N2 - A simple synthetic route to a new poly(diallylammonium) salt functionalized by a styrene group is presented. This reactive polymer was employed for polyelectrolyte multilayer films using electrostatical layer-by-layer self- assembly, together with an inorganic polyanion, namely an exfoliated hectorite clay. To enhance their stability, the final hybrid multilayers were cross-linked by exposure to UV light, leading only to a minor shrinkage. Alternatively, the reactive polycation was cross-linked after each adsorption step. X-ray reflectometry revealed that the two types of films dispose of an internal order with a short length scale, that seems insensitive to the photo-cross-linking. Cross- linking after each adsorption step, however, results in more regular film growth, and reduces the films? roughness and the amount of polyanion deposited. Under these conditions, the films seem to grow by deposition of submonolayers with a combined vertical and lateral expansion, resulting in the self-healing of previously deposited, incomplete layers. Y1 - 2002 ER - TY - JOUR A1 - Koetse, Marc M. A1 - Laschewsky, André A1 - Jonas, Alain M. A1 - Wagenknecht, W. T1 - The influence of charge density and distribution on the internal structure of electrostatically self-assembled polyelectrolyte films N2 - Electrostatically self-assembled (ESA) polyelectrolyte films show in general no internal structure. The use of special polycations, however, namely of lyotropic ionenes, may give rise to highly ordered coatings. In this article, the influence of the charge density of the polyanion, as well as the distribution of the charged groups within this polymer, is examined, using a series of anionic cellulose derivatives. Various techniques were used to study the films? growth and internal structure. Both showed to be affected in particular by the charge density but also by the substitution pattern. Y1 - 2002 ER - TY - JOUR A1 - Arotcarena, Michel A1 - Heise, Bettina A1 - Ishaya, Sultana A1 - Laschewsky, André T1 - Switching the inside and the outside of aggregates of water-soluble block copolymers with double thermoresponsivity N2 - Water-soluble block copolymers were prepared from the non-ionic monomer N-isopropylacrylamide (NIPA) and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]-ammonio propane sulfonate (SPP) by sequential free radical polymerization via the RAFT process. Such block copolymers with two hydrophilic blocks exhibit double thermo- responsive behavior in water: the poly-NIPA block shows a lower critical solution temperature, whereas the poly-SPP block exhibits an upper critical solution temperature. Appropriate design of the block lengths leads to block copolymers which stay in solution in the full temperature range between 0°C and 100°C. Both blocks of these polymers dissolve in water at intermediate temperatures, whereas at high temperatures, the poly-NIPA block forms colloidal hydrophobic associates that are kept in solution by the poly-SPP block, and at low temperatures, the poly-SPP block forms colloidal polar aggregates that are kept in solution by the poly-NIPA block. In this way, colloidal aggregates can be prepared in water which switch reversibly, and without any additive, their "inside" to the "outside", and vice versa. The aggregates provide microdomains and surfaces of different character, which can be controlled by a simple thermal stimulus. Y1 - 2002 ER - TY - JOUR A1 - Lunkenheimer, K. A1 - Laschewsky, André A1 - Warszynski, P. A1 - Hirte, R. T1 - On the adsorption behaviour of soluble, surface-chemically pure hemicyanine dyes at the air/water interface N2 - Equilibrium surface tension (se) versus concentration isotherms of surface-chemically pure aqueous solutions of the homologous series of N-n-alkyl-4'-(dimethylamino)-stilbaziumbromides ('hemicyanines') were measured at 295 K. The adsorption parameters of saturation adsorption and standard free energy of adsorption of the hemicyanines were determined from the evaluation of the se vs. c isotherms by using a two state approach to surface equation of state. The adsorption parameters reveal a very pronounced phenomenon of alternation (even/ odd- effect) which has so far not been met to a large extent like this. Thus, the cross-sectional areas of the odd members are almost twice those of the related even members. Surface activity of the odd is stronger than that of the even members. UV-Vis investigations showed that there is no indication of aggregate formation in the adsorption layer. The thermodynamic results give evidence for distinct differences between the surface conformations of the even- and the odd-chain hemicyanine dyes although the reasons for it are not known. Y1 - 2002 ER - TY - JOUR A1 - Virtanen, Janne A1 - Arotcarena, Michel A1 - Heise, Bettina A1 - Ishaya, Sultana A1 - Laschewsky, André A1 - Tenhu, Heikki T1 - Dissolution and aggregation of a poly (NIPA-block-sulfobetaine) copolymer in pure and saline aqueous solutions N2 - Thermal properties of block copolymer, poly(N-isopropyl acrylamide)-block-poly(3-[N-(3-methacrylamido-propyl)- N,N-dimethyl]-ammonio propane sulfonate), PNIPA-b-PSPP have been studied in pure and saline (NaCl) aqueous solutions by dynamic laser light scattering (DLS). The copolymer [Mw(PNIPA) 10800 g/mol and Mw(PSPP) 9700 g/mol] exhibits both an upper (UCST 9 oC) and lower (LCST 32 oC) critical solution temperatures in pure water. The addition of NaCl enhances the solubility of the zwitterionic polymer, PSPP, leading to the disappearance of the UCST. On the other hand, the solubility of PNIPA in water decreases as NaCl is added. At 20 oC the copolymer shows a bimodal size distribution through the NaCl concentration range of 0-0.93 M above a certain limiting polymer concentration. The slow and fast components of the diffusion coefficients of the polymer have been calculated. A gradual addition of salt turns the mutual interactions from zwitterionic attractions between PSPP blocks to hydrophobic attractions between PNIPA blocks. The formation of the aggregates and the aggregate sizes at T < UCST and T > LCST are influenced by polymer and salt concentrations. Below UCST the aggregates in saline polymer solutions are larger than those in pure polymer solutions. Above LCST the aggregate size is determined by the salt concentration. Y1 - 2002 ER - TY - JOUR A1 - Laschewsky, André T1 - Polymeric Surfactants N2 - The contribution gives an overview over polymeric surfactants that are suited to act as micellar polymers in aqueous media. The various polymer types are presented, and the characteristic property profiles distinguishing the classes are highlighted Y1 - 2003 ER - TY - JOUR A1 - Glinel, Karine A1 - Jonas, Alain M. A1 - Laschewsky, André A1 - Vuillaume, Pascal Y. T1 - Internally structured polyelectrolyte multilayers Y1 - 2003 SN - 3-527-30440-1 ER - TY - JOUR A1 - Arys, Xavier A1 - Fischer, Peter A1 - Jonas, Alain M. A1 - Koetse, Marc M. A1 - Legras, Roger A1 - Laschewsky, André A1 - Wischerhoff, Erik T1 - Ordered polyelectrolyte multilayers : rules governing layering in organic binary multilayers Y1 - 2003 ER - TY - JOUR A1 - Baussard, Jean-Francois A1 - Habib-Jiwan, Jean-Louis A1 - Laschewsky, André T1 - Enhanced Förster resonance energy transfer in electrostatically self-assembled multilayer films made from new fluorescent labeled polycations Y1 - 2003 ER - TY - JOUR A1 - Laschewsky, André T1 - Polymerized micelles with compartments Y1 - 2003 ER - TY - JOUR A1 - Yuillaume, P. Y. A1 - Glinel, Karine A1 - Jonas, Alain M. A1 - Laschewsky, André T1 - Ordered polyelectrolyte "Multilayers" : 6. Effect of the molecular parameters on the formation of hybrid multilayers complexing poly(diallylammonium) salt and exfoliated clay Y1 - 2003 ER - TY - JOUR A1 - Hennaux, P. A1 - Laschewsky, André T1 - Novel nonionic polymerisable surfactants based on sulfoxides : 2. Homo- and Copolymers Y1 - 2003 ER - TY - JOUR A1 - Rullens, F. A1 - Devillers, M. A1 - Laschewsky, André T1 - New regular, amphiphilic poly(ampholyte)s : synthesis and characterization N2 - Hydrophobically substituted diallylamines bearing a hexyl, dodecyl, or octadecyl chain were synthesized and homopolymerized as hydrochlorides. Copolymerixation of the diallylamines with maleic acid produces alternating copolymers. The copolymers behave as amphiphilic polyampholytes and dissolve best in the acidic or in the basic form. Only the colpolymer with the hexyl chain could be dissolved in aqueous solvents and shows hydrophobic associaiton. The copolymers with the longer alkyl chains require polar protic organic solvents. All polymers are amorphous, but show a superstructure in bulk due to their amphiphilicity Y1 - 2004 ER - TY - JOUR A1 - Laschewsky, André A1 - Mallwitz, Frank A1 - Baussard, Jean-Francois A1 - Cochin, Didier A1 - Fischer, Peter A1 - Habib-Jiwan, Jean-Louis A1 - Wischerhoff, Erik T1 - Aggregation phenomena in polyelectrolyte multilayers made from polyelectrolytes bearing bulky functional, hydrophobic fragments N2 - The functionalization of polyelectrolyte multilayers often implies the use of bulky functional fragments, attached to a standard polyelectrolyte matrix. Despite of the high density of non-charged, often hydrophobic substituents, regular film growth by sequential adsorption proceeds easily when an appropriate polyelectrolyte counter ion is chosen. However, the functional fragments may cluster or aggregate. This complication is particularly evident when using chromophores and fluorophores as bulky pendant groups. Attention has to be paid to this phenomenon for the design of functional polyelectrolyte films, as aggregation may modify crucially the properties. The use of charged spacer groups does not necessarily suppress the aggregation of functional side groups. Still, clustering and aggregation depend on the detailed system employed, and are not obligatory. In the case of cationic poly(acrylamide)s labeled with naphthalene and pyrene fluorophores, for instance, the polymers form intramolecular hydrophobic associates in solution, as indicated by strong excimer formation. But the polymers can undergo a conformational rearrangement upon adsorption so that they are decoiled in the adsorbed films. Analogous observations are made for polyanions bearing mesogenic biphenyls fragments. In contrast, polycations functionalized with the dye coumarin 343 show little aggregation in solution, but a marked aggregation in the ESA films Y1 - 2004 ER - TY - JOUR A1 - Baussard, Jean-Francois A1 - Habib-Jiwan, Jean-Louis A1 - Laschewsky, André A1 - Mertoglu, Murat A1 - Storsberg, Joachim T1 - New chain transfer agents for reversible addition-fragmentation chain transfer (RAFT) polymerisation in aqueous media : 1. Synthesis and stability in water N2 - New chain transfer agents for free radical polymerisation via reversible addition-fragmentation chain transfer (RAFT) were synthesised that are particularly suited for aqueous solution polymerisation. The new compounds bear dithioester and trithiocarbonate moieties as well as permanently ionic groups to confer solubility in water. Their stability against hydrolysis was studied, and compared with the one of a frequently employed water-soluble RAFT agent, using UV-Vis-spectroscopy and H-1-NMR measurements. An improved resistance to hydrolysis was found for the new RAFT agents compared to the reference one, providing good stabilities in the pH range between 1 and 8, and up to temperatures of 70 degreesC. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2004 ER - TY - JOUR A1 - Strehmel, Veronika A1 - Kraudelt, Heide A1 - Wetzel, Hendrik A1 - Gornitz, Eckhard A1 - Laschewsky, André T1 - Free radical polymerization of methacrylates in ionic liquids Y1 - 2004 SN - 0065-7727 ER - TY - JOUR A1 - Szczubialka, K. A1 - Moczek, Lukasz A1 - Goliszek, A. A1 - Nowakowska, M. A1 - Kotzev, Anton A1 - Laschewsky, André T1 - Characterization of hydrocarbon and fluorocarbon microdomains formed in aqueous solution of associative polymers : a molecular probe technique N2 - Fluorocarbon associative polymers of the polysoap type were studied using two fluorescent probes, 1- octanoylpyrene (OcPyH) and 1-perfluorooctanoylpyrene (OcPyF). In aqueous solution the polymers formed hydrophobic domains composed of hydrocarbon, fluorocarbon or both types of polymeric side chains, which could solubilize the probes. This resulted in the appearance of new fluorescence emission bands and changes in the fluorescence polarization of the probes. The differences in the solubilization properties of the polymers are discussed. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0022-1139 ER - TY - JOUR A1 - Mertoglu, Murat A1 - Laschewsky, André A1 - Skrabania, Katja A1 - Wieland, C. T1 - New water soluble agents for reversible addition-fragmentation chain transfer polymerization and their application in aqueous solutions N2 - A series of nonionic, anionic, and cationic water-soluble monomers bearing the (meth)acrylate, (meth)acrylamide, or styrene moiety were polymerized in water by free-radical polymerization via reversible addition- fragmentation chain transfer (RAFT). Several new water-soluble RAFT agents based on dithiobenzoate were employed that are water soluble independently of the pH. One of them bears a fluorophore, enabling unsymmetrical double end-group labeling as well as the preparation of fluorescent-labeled polymers. The temperature-dependent stability of the new RAFT agents against hydrolysis was studied. Controlled polymerization in aqueous solution was possible with styrenic, acrylic, and methacrylic monomers; molar masses increase with conversion, and polydispersities are relatively low. But RAFT polymerization failed for an anionic itaconate. Whereas polymerizations of methacrylamides were slow at temperatures below 60 degrees C, such conditions proved favorable for the RAFT polymerization of acrylates and methacrylates, to minimize hydrolysis of the dithioester end-group functionality, and to improve the preparation of block copolymers Y1 - 2005 SN - 0024-9297 ER - TY - JOUR A1 - Mertoglu, Murat A1 - Garnier, Sebastien A1 - Laschewsky, André A1 - Skrabania, Katja A1 - Storsberg, J. T1 - Stimuli responsive amphiphilic block copolymers for aqueous media synthesised via reversible addition fragmentation chain transfer polymerisation (RAFT) N2 - A series of RAFT agents was synthesised, and used to prepare various ionic. non-ionic and zwitterionic water- soluble polymers, in organic as well as in aqueous media. The RAFT process proved to be a powerful method to prepare functional polymers of complex structure. such as amphiphilic diblock and triblock copolymers. This includes polymers containing one or even two stimuli-sensitive hydrophilic blocks. Switching the hydrophilic character of a single or of several blocks by changing the PH, the temperature or the salt content demonstrated the variability of the molecular designs suited for stimuli-sensitive polymeric amphiphiles, and exemplified the concept of multiple-sensitive systems. (c) 2005 Published by Elsevier Ltd Y1 - 2005 SN - 0032-3861 ER - TY - JOUR A1 - Lutz, Jean-Francois A1 - Laschewsky, André T1 - Multicompartment micelles : has the long-standing dream become a reality? N2 - Multicompartment micelles are complex nanosized systems that possess a hydrosoluble shell and a hydrophobic core, which is characterized by segregated incompatible subdomains. With roots starting about ten years ago, the field of multi compartment micelles has evolved slowly, until recently when significant achievements have been made. The present article reviews strategies for building such micellar assemblies as well as morphological studies, highlights the future challenges, and discusses possible applications, which exploit the coexistence of differentiated nano- domains. Formation of multi compartment micelles using miktoarm stars mu-(polyethylethylene)(poly(ethylene oxide))(poly(perfluoropropylene oxide)) and a cryo-TEM image visualizing the process Y1 - 2005 SN - 1022-1352 ER - TY - JOUR A1 - Laschewsky, André A1 - Wattebled, Laurent A1 - Arotcarena, Michel A1 - Habib-Jiwan, Jean-Louis A1 - Rakotoaly, R. H. T1 - Synthesis and properties of cationic oligomeric surfactants N2 - Three series of new oligomeric cationic surfactants were synthesized. These amphiphiles are trimeric and tetrameric oligomeric quaternary ammonium chlorides, with spacer groups of different lengths separating the individual surfactant fragments. The properties of the compounds, such as Krafft temperatures, surface activity, micellization, viscosifying effects, foaming and solubilizing capacity, are studied. The influence of the degree of oligomerization and of the spacer group on the surfactant properties is discussed, in comparison with the analogous standard monomeric and dimeric ("gemini") surfactants. Typically, the evolution of the properties observed from standard to dimeric surfactants progresses with the trimers and tetramers, resulting for instance in extremely low critical micellization concentrations Y1 - 2005 SN - 0743-7463 ER - TY - JOUR A1 - Laschewsky, André A1 - Lunkenheimer, K. A1 - Rakotoaly, R. H. A1 - Wattebled, Laurent T1 - Spacer effects in dimeric cationic surfactants N2 - A series of dimeric cationic surfactants (gemini surfactants), which have spacer groups of varying length and flexibility, was synthesized. The series is derived from the parent compounds dodecyltrimethylammonium chloride or benzyldodecyldimethylammonium chloride. Characteristic surfactant properties of the dimeric ammonium compounds such as surface activity, micellization, viscosity effects, foaming, and solubilization, were studied with respect to the influence of the spacer group on the surfactant. For all properties, the influence of the length of the spacer group was predominant though the chemical nature of the spacer cannot be neglected Y1 - 2005 SN - 0303-402X ER - TY - JOUR A1 - Kubowicz, Stephan A1 - Baussard, Jean-Francois A1 - Lutz, Jean-Francois A1 - Thünemann, Andreas F. A1 - von Berlepsch, Hans A1 - Laschewsky, André T1 - Multicompartment micelles formed by self-assembly of linear ABC triblock copolymers in aqueous medium Y1 - 2005 ER - TY - JOUR A1 - Mallwitz, Frank A1 - Laschewsky, André T1 - Direct access to stable, freestanding polymer membranes by layer-by-layer assembly of polyelectrolytes N2 - A novel method to prepare ultrathin, freestanding polyelectrolyte films in pores, without the need of sacrificial precursor coatings, has been developed (see Figure). The freestanding films are stable under ambient conditions and suited for additional electrostatic self-assembly or surface modification. They can be specifically decomposed, whereas after thermal crosslinking, resistant films are obtained Y1 - 2005 SN - 0935-9648 ER - TY - JOUR A1 - Leporatti, S. A1 - Sczech, R. A1 - Riegler, H. A1 - Bruzzano, Stefano A1 - Storsberg, J. A1 - Loth, Fritz A1 - Jaeger, Werner A1 - Laschewsky, André A1 - Eichhorn, S. A1 - Donath, E. T1 - Interaction forces between cellulose microspheres and ultrathin cellulose films monitored by colloidal probe microscopy : effect of wet strength agents Y1 - 2005 ER - TY - JOUR A1 - Laschewsky, André A1 - Pound, Gwenaelle A1 - Skrabania, Katja A1 - Holdt, Hans-Joachim A1 - Teller, Joachim T1 - Unsymmetrical bifunctional trithiocarbonate as unexpected by-product in the synthesis of a dithioester RAFT agent N2 - The trithiocarbonate 2-(benzylsulfanylthiocarbonylsulfanyl) propanoic acid is formed as minor by-product in the synthesis of the dithioester 2-((2-phenylthioacetyl)sulfanyl) propanoic acid via the Grignard route. The mechanism for this side reaction is not clear. The isolated trithiocarbonate may act as unsymmetrical but bifunctional RAFT agent in the aqueous polymerization of N,N-dimethyl acrylamide. Therefore, it is important to separate it completely from the dithioester before engaging the latter in controlled free radical polymerization to guarantee a maximum control. Y1 - 2007 UR - http://www.springerlink.com/content/101551 U6 - https://doi.org/10.1007/s.00396-007-1653-5 SN - 0303-402X ER - TY - JOUR A1 - Strehmel, Veronika A1 - Laschewsky, André A1 - Wetzel, Hendrik T1 - Homopolymerization of a highly polar zwitterionic methacrylate in ionic liquids and its copolymerization with a non-polar methacrylate N2 - Free radical homo- and copolymerization of the highly polar 3-(N-[2-methacryloyloxyethyl]-N,N-dimethylammonio) propane sulfonate with the nonpolar n-butylmethacrylate was investigated in the ionic liquids 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluoro phosphate, and compared to analogous polymerizations in standard solvents. Higher molar masses are obtained for the zwitterionic homopolymer when the polymerization is carried out in an ionic liquid compared to the classical reaction in water. Although homopolymerization of the sulfobetain monomer as well as of n-butylmethacrylate results in phase separation during the polymerization process, copolymerization of a stoichiometric ratio of the two monomers in the ionic liquids produced transparent gels indicating that no macrophase separation occurs. The use of ionic liquids as reaction medium improved the copolymerization behavior of the two methacrylates significantly. Whereas only minor amounts of n-butyl methacrylate were incorporated in the copolymer when synthesized in acetonitrile, the content of the non-polar monomer units in the zwitterionic copolymer approached increasingly its content in the polymerization mixture when ionic liquids were employed as solvents Y1 - 2006 ER - TY - JOUR A1 - Garnier, Sebastien A1 - Laschewsky, André T1 - New amphiphilic diblock copolymers : surfactant properties and solubilization in their micelles N2 - Several series of amphiphilic diblock copolymers are investigated as macrosurfactants in comparison to reference low-molar-mass and polymeric surfactants. The various copolymers share poly(butyl acrylate) as a common hydrophobic block but are distinguished by six different hydrophilic blocks (one anionic, one cationic, and four nonionic hydrophilic blocks) with various compositions. Dynamic light scattering experiments indicate the presence of micelles over the whole concentration range from 10(-4) to 10 g(.)L(-1). Accordingly, the critical micellization concentrations are very low. Still, the surface tension of aqueous solutions of block copolymers decreases slowly but continuously with increasing concentration, without exhibiting a plateau. The longer the hydrophobic block, the shorter the hydrophilic block, and the less hydrophilic the monomer of the hydrophilic block is, the lower the surface tension is. However, the effects are small, and the copolymers reduce the surface tension much less than standard low-molar-mass surfactants. Also, the copolymers foam much less and even act as anti-foaming agents in classical foaming systems composed of standard surfactants. The copolymers stabilize O/W emulsions made of methyl palmitate as equally well as standard surfactants but are less efficient for O/W emulsions made of tributyrine. However, the copolymer micelles exhibit a high solubilization power for hydrophobic dyes, probably at their core-corona interface, in dependence on the initial geometry of the micelles and the composition of the block copolymers. Whereas micelles of copolymers with strongly hydrophilic blocks are stable upon solubilization, solubilization-induced micellar growth is observed for copolymers with moderately hydrophilic blocks Y1 - 2006 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La0600595 SN - 0743-7463 ER - TY - JOUR A1 - Delorme, Nicolas A1 - Dubois, Monique A1 - Garnier, Sebastien A1 - Laschewsky, André A1 - Weinkamer, Richard A1 - Zemb, Thomas A1 - Fery, Andreas T1 - Surface immobilization and mechanical properties of catanionic hollow faceted polyhedrons N2 - We report here for the first time on surface immobilization of hollow faceted polyhedrons formed from catanionic surfactant mixtures. We find that electrostatic interaction with the substrate dominates their adhesion behavior. Using polyelectrolyte coated surfaces with tailored charge densities, polyhedrons can thus be immobilized without complete spreading, which allows for further study of their mechanical properties using AFM force measurements. The elastic response of individual polyhedrons can be locally resolved, showing pronounced differences in stiffness between faces and vertexes of the structure, which makes these systems interesting as models for structurally similar colloidal scale objects such as viruses, where such effects are predicted but cannot be directly observed due to the smaller dimensions. Elastic constants of the wall material are estimated using shell and plate deformation models and are found to be a factor of 5 larger than those for neutral lipidic bilayers in the gel state. We discuss the molecular origins of this high stiffness Y1 - 2006 UR - http://pubs.acs.org/journal/jpcbfk U6 - https://doi.org/10.1021/Jp054473+ SN - 1520-1758 ER - TY - JOUR A1 - Laschewsky, André A1 - Garnier, Sebastien A1 - Kirsten, Juliane A1 - Mertoglu, Murat A1 - Skrabania, Katja A1 - Lutz, Jean-Francois T1 - Comb-like polymeric surfactants by combining block and graft copolymer architectures Y1 - 2006 SN - 0065-7727 ER - TY - GEN A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Wischerhoff, Erik T1 - Modulating the solubility of zwitterionic poly((3- methacrylamidopropyl)ammonioalkane sulfonate)s in water and aqueous salt solutions via the spacer group separating the cationic and the anionic moieties N2 - Complementary to the well-established zwitterionic monomer 3-((3-methacrylamidopropyl)dimethylammonio) propane-1-sulfonate (SPP), the closely related monomers 2-hydroxy-3-((3-methacrylamidopropyl) dimethylammonio)propane-1-sulfonate (SHPP) and 4-((3-methacrylamidopropyl)dimethylammonio)-butane-1-sulfonate (SBP) were synthesised and polymerised by reversible addition–fragmentation chain transfer (RAFT) polymerisation, using a fluorophore labeled RAFT agent. The polyzwitterions of systematically varied molar masses were characterised with respect to their solubility in water and aqueous salt solutions. Both poly(sulfobetaine)s show thermoresponsive behaviour in water, exhibiting phase separation at low temperatures and upper critical solution temperatures (UCST). For both polySHPP and polySBP, cloud points depend notably on the molar mass, and are much higher in D2O than in H2O. Also, the cloud points are effectively modulated by the addition of salts. The individual effects can be in parts correlated to the Hofmeister series for the anions studied. Still, they depend in a complex way on the concentration and the nature of the added electrolytes, on the one hand, and on the detailed nature of the spacer group separating the anionic and the cationic charges of the betaine moiety, on the other hand. As anticipated, the cloud points of polySBP are much higher than the ones of the analogous polySPP of identical molar mass. Surprisingly, the cloud points of polySHPP are also somewhat higher than the ones of their polySPP analogues, despite the additional hydrophilic hydroxyl group present in the spacer separating the ammonium and the sulfonate moieties. These findings point to a complicated interplay of the various hydrophilic components in polyzwitterions with respect to their overall hydrophilicity. Thus, the spacer group in the betaine moiety proves to be an effective additional molecular design parameter, apparently small variations of which strongly influence the phase behaviour of the polyzwitterions in specific aqueous environments. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 309 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-103040 SP - 731 EP - 740 ER - TY - GEN A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Päch, Michael A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates) N2 - A series of new sulfobetaine methacrylates, including nitrogen-containing saturated heterocycles, was synthesised by systematically varying the substituents of the zwitterionic group. Radical polymerisation via the RAFT (reversible addition–fragmentation chain transfer) method in trifluoroethanol proceeded smoothly and was well controlled, yielding polymers with predictable molar masses. Molar mass analysis and control of the end-group fidelity were facilitated by end-group labeling with a fluorescent dye. The polymers showed distinct thermo-responsive behaviour of the UCST (upper critical solution temperature) type in an aqueous solution, which could not be simply correlated to their molecular structure via an incremental analysis of the hydrophilic and hydrophobic elements incorporated within them. Increasing the spacer length separating the ammonium and the sulfonate groups of the zwitterion moiety from three to four carbons increased the phase transition temperatures markedly, whereas increasing the length of the spacer separating the ammonium group and the carboxylate ester group on the backbone from two to three carbons provoked the opposite effect. Moreover, the phase transition temperatures of the analogous polyzwitterions decreased in the order dimethylammonio > morpholinio > piperidinio alkanesulfonates. In addition to the basic effect of the polymers’ precise molecular structure, the concentration and the molar mass dependence of the phase transition temperatures were studied. Furthermore, we investigated the influence of added low molar mass salts on the aqueous-phase behaviour for sodium chloride and sodium bromide as well as sodium and ammonium sulfate. The strong effects evolved in a complex way with the salt concentration. The strength of these effects depended on the nature of the anion added, increasing in the order sulfate < chloride < bromide, thus following the empirical Hofmeister series. In contrast, no significant differences were observed when changing the cation, i.e. when adding sodium or ammonium sulfate. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 298 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102028 ER - TY - GEN A1 - Comminges, Clément A1 - Frasca, Stefano A1 - Sütterlin, Martin A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Wollenberger, Ursula T1 - Surface modification with thermoresponsive polymer brushes for a switchable electrochemical sensor N2 - Elaboration of switchable surfaces represents an interesting way for the development of a new generation of electrochemical sensors. In this paper, a method for growing thermoresponsive polymer brushes from a gold surface pre-modified with polyethyleneimine (PEI), subsequent layer-by-layer polyelectrolyte assembly and adsorption of a charged macroinitiator is described. We propose an easy method for monitoring the coil-to-globule phase transition of the polymer brush using an electrochemical quartz crystal microbalance with dissipation (E-QCM-D). The surface of these polymer modified electrodes shows reversible switching from the swollen to the collapsed state with temperature. As demonstrated from E-QCM-D measurements using an original signal processing method, the switch is operating in three reversible steps related to different interfacial viscosities. Moreover, it is shown that the one electron oxidation of ferrocene carboxylic acid is dramatically affected by the change from the swollen to the collapsed state of the polymer brush, showing a spectacular 86% decrease of the charge transfer resistance between the two states. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 287 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-99471 ER - TY - GEN A1 - Inal, Sahika A1 - Kölsch, Jonas D. A1 - Chiappisi, Leonardo A1 - Janietz, Dietmar A1 - Gradzielski, Michael A1 - Laschewsky, André A1 - Neher, Dieter T1 - Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers N2 - We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 251 KW - anionic polymerizations KW - dilute aqueous-solutions KW - ether methacrylates KW - n-isopropylacrylamide KW - oligo(ethylene glycol) methacrylate KW - phase-transitions KW - protein interactions KW - solvatochromic fluorophore KW - thermoresponsive polymers KW - to-coil transition Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95379 SP - 6603 EP - 6612 ER - TY - GEN A1 - Inal, Sahika A1 - Kölsch, Jonas D. A1 - Sellrie, Frank A1 - Schenk, Jörg A. A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Neher, Dieter T1 - A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein N2 - We present two thermoresponsive water soluble copolymers prepared via free radical statistical copolymerization of N-isopropylacrylamide (NIPAm) and of oligo(ethylene glycol) methacrylates (OEGMAs), respectively, with a solvatochromic 7-(diethylamino)-3-carboxy-coumarin (DEAC)- functionalized monomer. In aqueous solutions, the NIPAm-based copolymer exhibits characteristic changes in its fluorescence profile in response to a change in solution temperature as well as to the presence of a specific protein, namely an anti-DEAC antibody. This polymer emits only weakly at low temperatures, but exhibits a marked fluorescence enhancement accompanied by a change in its emission colour when heated above its cloud point. Such drastic changes in the fluorescence and absorbance spectra are observed also upon injection of the anti-DEAC antibody, attributed to the specific binding of the antibody to DEAC moieties. Importantly, protein binding occurs exclusively when the polymer is in the well hydrated state below the cloud point, enabling a temperature control on the molecular recognition event. On the other hand, heating of the polymer–antibody complexes releases a fraction of the bound antibody. In the presence of the DEAC-functionalized monomer in this mixture, the released antibody competitively binds to the monomer and the antibody-free chains of the polymer undergo a more effective collapse and inter-aggregation. In contrast, the emission properties of the OEGMA-based analogous copolymer are rather insensitive to the thermally induced phase transition or to antibody binding. These opposite behaviours underline the need for a carefully tailored molecular design of responsive polymers aimed at specific applications, such as biosensing. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 249 KW - intramolecular charge-transfer KW - phase-transitions KW - responsive polymers KW - sensitivity KW - thermometer KW - dyes KW - modulation KW - assemblies KW - antibodies KW - binding Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95336 SP - 6373 EP - 6381 ER - TY - GEN A1 - Biddle, M. B. A1 - Rickert, S. E. A1 - Lando, J. B. A1 - Laschewsky, André T1 - The use of the Langmuir-Blodgett technique to obtain ultra-thin polar films N2 - The piezoelectric and pyroelectric properties of oriented films possessing dipole moments are increasingly being used in pressure, acoustic, thermal and optical devices. The performance of these devices in many applications may be enhanced by thin-film technology.The developing Langmuir-Blodgett thin-film deposition technique offers the opportunity to obtain highly oriented and uniform organic-based films in the 10–5000 nm thickness range. Special techniques must be used, however, to assemble these molecules in such a way as to result in polar multilayer films. Several possible deposition techniques are investigated, with one resulting in a polar and pyroelectric film about 50 nm thick. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 098 Y1 - 1989 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17185 ER - TY - GEN A1 - Tsukruk, Vladimir A1 - Mischenko, Nikolay A1 - Köberle, Peter A1 - Laschewsky, André T1 - The structural order of some novel ionic polymers; 2. : Models of molecular packing N2 - The molecular packing and spatial correlations of two isomeric zwitterionic polymethacrylates and one polyacrylate analog are studied by means of X-ray analysis and conformational calculations. The analysis of the correlation functions and density distribution profiles suggest a double-layered molecular packing which is discussed for the three polymers investigated, with respect to their different chemical structures. Whereas the zwitterionic polymethacrylates studied exhibit liquid-like short-range order, the polyacrylate analog exhibits an ordered double-layered superstructure. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 096 Y1 - 1992 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17256 ER - TY - GEN A1 - Elbert, R. A1 - Laschewsky, André A1 - Ringsdorf, H. T1 - Hydrophilic spacer groups in polymerizable lipids: formation of biomembrane models from bulk polymerized lipids N2 - A variety of polymerizable lipids containing a hydrophilic spacer group between the reactive group and the main amphiphilic structure have been synthesized. They were investigated in monolayers, liposomes, and multilayers. When the spacer concept was used, efficient decoupling of the motions of the polymeric chain and the amphiphilic side groups is achieved. Thus, the often found loss of the important fluid phases by polymerization is avoided. Polymeric monolayers of the spacer lipid, prepared either by polymerization in the monolayer or by spreading of prepolymerized lipid, exhibit nearly identical surface pressure-area diagrams. Most distinctly, the successful decoupling of the motions of the polymer main chain and the membrane forming amphiphilic side groups is demonstrated by the self-organization of bulk polymerized spacer lipids to polymeric liposomes. In addition, spacer lipids are able to build polymeric Langmuir-Blodgett multilayers. The decoupling of the polymer main chain and the membrane-forming amphiphilic side groups enables the deposition of already polymeric monolayers onto supports to form defined multilayers. If, alternatively, monomeric monolayers are deposited and polymerized on the support, defects in the layers due to structural changes during the polymerization are avoided by the flexible spacer group. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 095 Y1 - 1985 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17361 ER - TY - GEN A1 - Lupo, Donald A1 - Prass, Werner A1 - Scheunemann, Ude A1 - Laschewsky, André A1 - Ringsdorf, Helmut A1 - Ledoux, Isabelle T1 - Second-harmonic generation in Langmuir-Blodgett monolayers of stilbazium salt and phenylhydrazone dyes N2 - Contents: 1. INTRODUCTION 2. SYNTHESIS OF THE COMPOUNDS 3. PREPARATION AND CHARACTERIZATION OF MONOLAYERS A. Monolayer Isotherms B. Langmuir-Blodgett Monolayer Films 4. EXPERIMENTAL SETUP FOR NONLINEAR MEASUREMENTS 5. NONLINEAR OPTICAL PROPERTIES 6. DISCUSSION 7. CONCLUSION T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 094 Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17401 ER - TY - GEN A1 - Rozanski, Stanislaw A. A1 - Kremer, Friedrich A1 - Köberle, Peter A1 - Laschewsky, André T1 - Relaxation and charge transport in mixtures of zwitterionic polymers and inorganic salts N2 - Dielectric spectroscopy is employed to analyze the molecular dynamics and the charge transport in mixtures of zwitterionic polymers of the type poly{3 [N(-methacryloyloxyalkyl)] N, [N-dimethylammonio propanesulfonate] with sodium iodide in the frequency range of 10²Hz-10(up)7 Hz and in the temperature range of 110 K-400 K. The amount of inorganic salt added varies from 0-200 mol-% relative to the number of zwitterionic groups present in the polymer, contributing strongly to the conductivity. One relaxation process is observed whose relaxation rate depends strongly on the length of the aliphatic spacer between the polymethacrylate main chain and the zwitterionic group. Exhibiting an Arrhenius-like temperature depence with activation energy EA = 47 KJ/mol, this relaxation process is assigned to fluctuation of the quaternary ammonium groups in the side chains. At higher temperatures, the dielectric properties and the conductivity are primarily dominated by the mobile inorganic ions: conductivity strongly depends on the salt concentration, showing a pronounced electrode polarization effect. The frequency and salt concentration, dependences of the conductivity can be quantitatively described as hopping of charge carriers being subject to spatially randomly varying energy barriers. For the low-frequency regime and for the critical frequency marking the onset of the conductivity's dispersion, the Barton-Nakajima-Namikawa (BNN) relationship is fulfilled. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 093 Y1 - 1995 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17438 ER -