TY - JOUR A1 - Comminges, Clement A1 - Frasca, Stefano A1 - Suetterlin, Martin A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Wollenberger, Ursula T1 - Surface modification with thermoresponsive polymer brushes for a switchable electrochemical sensor JF - RSC Advances 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. Y1 - 2014 U6 - https://doi.org/10.1039/c4ra07190e SN - 2046-2069 VL - 4 IS - 81 SP - 43092 EP - 43097 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Zehm, Daniel T1 - On the hydrophilicity of polyzwitterion poly (N, N-dimethyl-N(3-(methacrylamido)propyl)ammoniopropane sulfonate) in water, deuterated water, and aqueous salt solutions JF - Journal of biomaterials science : Polymer edition KW - polyzwitterion KW - sulfobetaine KW - synthesis KW - fluorescence label KW - upper critical solution temperature KW - isotope effect KW - anti-polyelectrolyte effect Y1 - 2014 U6 - https://doi.org/10.1080/09205063.2014.939918 SN - 0920-5063 SN - 1568-5624 VL - 25 IS - 14-15 SP - 1602 EP - 1618 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Kopec, Maciej A1 - Lapok, Lukasz A1 - Laschewsky, André A1 - Zapotoczny, Szczepan A1 - Nowakowska, Maria T1 - Polyelectrolyte multilayers with perfluorinated phthalocyanine selectively entrapped inside the perfluorinated nanocompartments JF - Soft matter N2 - A novel perfluorinated magnesium phthalocyanine (MgPcF64) was synthesized and employed to probe nanodomains in hydrophobically modified, amphiphilic cationic polyelectrolytes bearing alkyl and/or fluoroalkyl side chains. MgPcF64 was found to be solubilized exclusively in the aqueous solutions of the fluorocarbon modified polycations, occupying the perfluorinated nanocompartments provided, while analogous polyelectrolytes with alkyl side chains forming hydrocarbon nanocompartments could not host the MgPcF64 dye. Multilayer films were fabricated by means of the layer-by-layer (LbL) deposition method using sodium poly(styrene sulfonate) as a polyanion. Linear multilayer growth was confirmed by UV-Vis spectroscopy and spectroscopic ellipsometry. Atomic force microscopy studies indicated that the micellar conformation of the polycations is preserved in the multilayer films. Fluorescence spectroscopy measurements confirmed that MgPcF64 stays embedded inside the fluorocarbon domains after the deposition process. This facile way of selectively incorporating water-insoluble, photoactive molecules into the structure of polyelectrolyte multilayers may be utilized for nanoengineering of ultrathin film-based optoelectronic devices. Y1 - 2014 U6 - https://doi.org/10.1039/c2sm26938d SN - 1744-683X SN - 1744-6848 VL - 10 IS - 10 SP - 1481 EP - 1488 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kopec, Maciej A1 - Niemiec, Wiktor A1 - Laschewsky, André A1 - Nowakowska, Maria A1 - Zapotoczny, Szczepan T1 - Photoinduced energy and electron transfer in micellar multilayer films JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Micellar multilayer films were prepared from an amphiphilic comb-like polycation ("polysoap") and the polyanion poly(styrene sulfonate) (PSS) using alternate polyelectrolyte layer-by-layer (LbL) self-assembly. Linear growth of the film thickness was evidenced by UV-vis spectroscopy and spectroscopic ellipsometry. Imaging by atomic force microscopy (AFM) indicated that the micellar conformation adopted by the polycation in solutions was preserved in the films. Thus, hydrophobic photoactive molecules, which were solubilized by the hydrophobic nanodomains of the micellar polymer prior to deposition, could be transferred into the films. Photoinduced energy transfer was observed in the nanostructured multilayers between naphthalene (donor) and perylene (acceptor) molecules embedded inside the polymer micelles. The efficiency of the energy transfer process can be controlled to some extent by introducing spacer layers between the layers containing the donor or acceptor, revealing partial stratification of the micellar LbL films. Also, photoinduced electron transfer was evidenced between perylene (donor) and butyl viologen (acceptor) molecules embedded inside the multilayers by steady-state fluorescence spectroscopy. The obtained photoactive nanostructures are promising candidates for solar-to-chemical energy conversion systems. Y1 - 2014 U6 - https://doi.org/10.1021/jp410808z SN - 1932-7447 VL - 118 IS - 4 SP - 2215 EP - 2221 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kyriakos, Konstantinos A1 - Aravopoulou, Dionysia A1 - Augsbach, Lukas A1 - Sapper, Josef A1 - Ottinger, Sarah A1 - Psylla, Christina A1 - Rafat, Ali Aghebat A1 - Benitez-Montoya, Carlos Adrian A1 - Miasnikova, Anna A1 - Di, Zhenyu A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Kyritsis, Apostolos A1 - Papadakis, Christine M. T1 - Novel thermoresponsive block copolymers having different architectures-structural, rheological, thermal, and dielectric investigations JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - Thermoresponsive block copolymers comprising long, hydrophilic, nonionic poly(methoxy diethylene glycol acrylate) (PMDEGA) blocks and short hydrophobic polystyrene (PS) blocks are investigated in aqueous solution. Various architectures, namely diblock, triblock, and starblock copolymers are studied as well as a PMDEGA homopolymer as reference, over a wide concentration range. For specific characterization methods, polymers were labeled, either by partial deuteration (for neutron scattering studies) or by fluorophores. Using fluorescence correlation spectroscopy, critical micellization concentrations are identified and the hydrodynamic radii of the micelles, r (h) (mic) , are determined. Using dynamic light scattering, the behavior of r (h) (mic) in dependence on temperature and the cloud points are measured. Small-angle neutron scattering enabled the detailed structural investigation of the micelles and their aggregates below and above the cloud point. Viscosity measurements are carried out to determine the activation energies in dependence on the molecular architecture. Differential scanning calorimetry at high polymer concentration reveals the glass transition of the polymers, the fraction of uncrystallized water and effects of the phase transition at the cloud point. Dielectric relaxation spectroscopy shows that the polarization changes reversibly at the cloud point, which reflects the formation of large aggregates upon heating through the cloud point and their redissolution upon cooling. KW - Block copolymers KW - Thermoresponsive KW - Structural investigations KW - Mechanical properties KW - Thermal behavior KW - Dielectric properties Y1 - 2014 U6 - https://doi.org/10.1007/s00396-014-3282-0 SN - 0303-402X SN - 1435-1536 VL - 292 IS - 8 SP - 1757 EP - 1774 PB - Springer CY - New York ER - TY - JOUR A1 - Kyriakos, Konstantinos A1 - Philipp, Martine A1 - Adelsberger, Joseph A1 - Jaksch, Sebastian A1 - Berezkin, Anatoly V. A1 - Lugo, Dersy M. A1 - Richtering, Walter A1 - Grillo, Isabelle A1 - Miasnikova, Anna A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Cononsolvency of water/methanol mixtures for PNIPAM and PS-b-PNIPAM: pathway of aggregate formation investigated using time-resolved SANS JF - Macromolecules : a publication of the American Chemical Society N2 - We investigate the cononsolvency effect of poly(N-isopropylacrylamide) (PNIPAM) in mixtures of water and methanol. Two systems are studied: micellar solutions of polystyrene-b-poly(N-isopropylacrylamide) (PS-b-PNIPAM) diblock copolymers and, as a reference, solutions of PNIPAM homopolymers, both at a concentration of 20 mg/mL in DO. Using a stopped-flow instrument, fully deuterated methanol was rapidly added to these solutions at volume fractions between 10 and 20%. Time-resolved turbidimetry revealed aggregate formation within 10-100 s. The structural changes on mesoscopic length scales were followed by time-resolved small-angle neutron scattering (TR-SANS) with a time resolution of 0.1 s. In both systems, the pathway of the aggregation depends on the content of deuterated methanol; however, it is fundamentally different for homopolymer and diblock copolymer solutions: In the former, very large aggregates (>150 nm) are formed within the dead time of the setup, gradient appears at their surface in the late stages. In contrast, the growth of the aggregates in the latter system features different regimes, and the final aggregate size is 50 nm, thus much smaller than for the homopolymer. For the diblock copolymer, the time dependence of the aggregate radius can be described by two models: In the initial stage, the diffusion-limited coalescence model describes the data well; however, the resulting coalescence time is unreasonably high. In the late stage, a logarithmic coalescence model based on an energy barrier which is proportional to the aggregate radius is successfully applied. and a concentration Y1 - 2014 U6 - https://doi.org/10.1021/ma501434e SN - 0024-9297 SN - 1520-5835 VL - 47 IS - 19 SP - 6867 EP - 6879 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Laschewsky, André T1 - Structures and synthesis of zwitterionic polymers JF - Polymers N2 - The structures and synthesis of polyzwitterions ("polybetaines") are reviewed, emphasizing the literature of the past decade. Particular attention is given to the general challenges faced, and to successful strategies to obtain polymers with a true balance of permanent cationic and anionic groups, thus resulting in an overall zero charge. Also, the progress due to applying new methodologies from general polymer synthesis, such as controlled polymerization methods or the use of "click" chemical reactions is presented. Furthermore, the emerging topic of responsive ("smart") polyzwitterions is addressed. The considerations and critical discussions are illustrated by typical examples. KW - review KW - polyzwitterion KW - polyampholyte KW - zwitterionic group KW - betaine KW - synthesis KW - monomer KW - polymerization KW - post-polymerization modification Y1 - 2014 U6 - https://doi.org/10.3390/polym6051544 SN - 2073-4360 VL - 6 IS - 5 SP - 1544 EP - 1601 PB - MDPI CY - Basel ER - TY - JOUR A1 - Ortmann, Thomas A1 - Ahrens, Heiko A1 - Milewski, Sven A1 - Lawrenz, Frank A1 - Groening, Andreas A1 - Laschewsky, André A1 - Garnier, Sebastien A1 - Helm, Christiane A. T1 - Lipid monolayers with adsorbed oppositely charged polyelectrolytes: Influence of reduced charge densities JF - Polymers N2 - Polyelectrolytes in dilute solutions (0.01 mmol/L) adsorb in a two-dimensional lamellar phase to oppositely charged lipid monolayers at the air/water interface. The interchain separation is monitored by Grazing Incidence X-ray Diffraction. On monolayer compression, the interchain separation decreases to a factor of two. To investigate the influence of the electrostatic interaction, either the line charge density of the polymer is reduced (a statistic copolymer with 90% and 50% charged monomers) or mixtures between charged and uncharged lipids are used (dipalmitoylphosphatidylcholine (DPPC)/dioctadecyldimethylammonium bromide (DODAB)) On decrease of the surface charge density, the interchain separation increases, while on decrease of the linear charge density, the interchain separation decreases. The ratio between charged monomers and charged lipid molecules is fairly constant; it decreases up to 30% when the lipids are in the fluid phase. With decreasing surface charge or linear charge density, the correlation length of the lamellar order decreases. KW - lipid monolayer KW - polyelectrolyte adsorption KW - statistical copolymer KW - two-dimensional phases KW - surface charge KW - nematic phase KW - grazing incidence X-ray diffraction Y1 - 2014 U6 - https://doi.org/10.3390/polym6071999 SN - 2073-4360 VL - 6 IS - 7 SP - 1999 EP - 2017 PB - MDPI CY - Basel ER - TY - JOUR A1 - Weiss, Jan A1 - Wienk, Hans A1 - Boelens, Rolf A1 - Laschewsky, André T1 - Block copolymer micelles with an intermediate star-/flower-like structure studied by H-1 NMR relaxometry JF - Macromolecular chemistry and physics N2 - H-1 NMR relaxation is used to study the self-assembly of a double thermoresponsive diblock copolymer in dilute aqueous solution. Above the first transition temperature, at which aggregation into micellar structures is observed, the trimethylsilyl (TMS)-labeled end group attached to the shell-forming block shows a biphasic T-2 relaxation. The slow contribution reflects the TMS groups located at the periphery of the hydrophilic shell, in agreement with a star-like micelle. The fast T-2 contribution corresponds to the TMS groups, which fold back toward the hydrophobic core, reflecting a flower-like micelle. These results confirm the formation of block copolymer micelles of an intermediate nature (i.e., of partial flower-like and star-like character), in which a part of the TMS end groups folds back to the core due to hydrophobic interactions. KW - block copolymers KW - polymer micelles KW - relaxation NMR spectroscopy KW - self-assembly KW - thermoresponsive materials Y1 - 2014 U6 - https://doi.org/10.1002/macp.201300753 SN - 1022-1352 SN - 1521-3935 VL - 215 IS - 9 SP - 915 EP - 919 PB - Wiley-VCH CY - Weinheim ER -