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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - Hennaux, P. A1 - Laschewsky, André T1 - Novel nonionic polymerisable surfactants based on sulfoxides : 2. Homo- and Copolymers 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 - Laschewsky, André T1 - Polymerized micelles with compartments 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 -