TY - JOUR A1 - Koeth, Anja A1 - Appelhans, Dietmar A1 - Robertson, Daniela A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Use of weakly cationic dendritic glycopolymer for morphological transformation of phospholipid vesicles into tube-like networks JF - Soft matter N2 - Using cationic polyelectrolytes with different molecular architectures, only hyperbranched poly(ethyleneimine) with maltose shell is suited to tailor the morphological transformation of anionic vesicles into tube-like networks. The interaction features of those materials partly mimic biological features of tubular proteins in nature. Y1 - 2011 U6 - https://doi.org/10.1039/c1sm06439h SN - 1744-683X VL - 7 IS - 22 SP - 10581 EP - 10584 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Wegener, Michael A1 - Wirges, Werner A1 - Fohlmeister, Jens Bernd A1 - Tiersch, Brigitte A1 - Gerhard, Reimund T1 - Two-step inflation of cellular polypropylene films: Void-thickness increase and enhanced electromechanical properties N2 - In cellular, electromechanically active polymer films, the so-called ferroelectrets, the cell size and shape distributions can be varied through a controlled inflation process. Up to now, high-pressure treatments were usually performed at elevated temperatures. There are, however, significant experimental limitations and complications if the pressure and temperature treatments are performed at the same time. Here, we demonstrate the controlled inflation of cellular polypropylene films by means of sepal-ate pressure and temperature treatments. Separate procedures are Much easier to implement. Excellent electromechanical properties were achieved with Such a two-step inflation process. The technique has significant potential for inflating large-area transducer films for electromechanical and electroacoustical applications Y1 - 2004 ER - TY - JOUR A1 - Couturier, Jean-Philippe A1 - Wischerhoff, Erik A1 - Bernin, Robert A1 - Hettrich, Cornelia A1 - Koetz, Joachim A1 - Sutterlin, Martin A1 - Tiersch, Brigitte A1 - Laschewsky, Andre T1 - Thermoresponsive Polymers and Inverse Opal Hydrogels for the Detection of Diols JF - Langmuir N2 - Responsive inverse opal hydrogels functionalized by boroxole moieties were synthesized and explored as sensor platforms for various low molar mass as well as polymeric diols and polyols, including saccharides, glycopolymers and catechols, by exploiting the diol induced modulation of their structural color. The underlying thermoresponsive water-soluble copolymers and hydrogels exhibit a coil-to-globule or volume phase transition, respectively, of the LCST-type. They were prepared from oligoethylene oxide methacrylate (macro)monomers and functionalized via copolymerization to bear benzoboroxole moieties. The resulting copolymers represent weak polyacids, which can bind specifically to diols within an appropriate pH window. Due to the resulting modulation of the overall hydrophilicity of the systems and the consequent shift of their phase transition temperature, the usefulness of such systems for indicating the presence of catechols, saccharides, and glycopolymers was studied, exploiting the diol/polyol induced shifts of the soluble polymers’ cloud point, or the induced changes of the hydrogels’ swelling. In particular, the increased acidity of benzoboroxoles compared to standard phenylboronic acids allowed performing the studies in PBS buffer (phosphate buffered saline) at the physiologically relevant pH of 7.4. The inverse opals constructed of these thermo- and analyte-responsive hydrogels enabled following the binding of specific diols by the induced shift of the optical stop band. Their highly porous structure enabled the facile and specific optical detection of not only low molar mass but also of high molar mass diol/polyol analytes such as glycopolymers. Accordingly, such thermoresponsive inverse opal systems functionalized with recognition units represent attractive and promising platforms for the facile sensing of even rather big analytes by simple optical means, or even by the bare eye. Y1 - 2016 U6 - https://doi.org/10.1021/acs.langmuir.6b00803 SN - 0743-7463 VL - 32 SP - 4333 EP - 4345 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Secker, Christian A1 - Voelkel, Antje A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Thermo-Induced Aggregation and Crystallization of Block Copolypeptoids in Water JF - Macromolecules : a publication of the American Chemical Society N2 - Block copolypeptoids comprising a thermosensitive, crystallizable poly(N-(n-propyl)glycine) block and a watersoluble poly(N-methylglycine) block, P70My (y = 23, 42, 76, 153, and 290), were synthesized bY ring-opening polymerization of the corresponding N-alkylglycine N-carboxyanhydrides (NCAs) and examined according to their thermo-induced aggregation and crystallization in water by turbidimetty, micro-differential scanning calorimetry (micro-DSC); cryogenic scanning electron microscopy (cryo-SEM), analytical ultracentrifugation (AUC), and static light scattering (SLS). At a temperature above the cloud point temperature, the initially formed micellar aggregates started to crystallize and grow into larger complex assemblies of about 100-500 nm, exhibiting flower-like (P70M23), ellipsoidal (P70M42 and P70M72) or irregular shapes (P70M153 and.P70M290). Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.5b02481 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 979 EP - 985 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wellert, Stefan A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Richardt, Andre A1 - Lapp, Alain A1 - Holderer, Olaf A1 - Gaeb, Juergen A1 - Blum, Marc-Michael A1 - Schulreich, Christoph A1 - Stehle, Ralf A1 - Hellweg, Thomas T1 - The DFPase from Loligo vulgaris in sugar surfactant-based bicontinuous microemulsions structure, dynamics, and enzyme activity JF - European biophysics journal : with biophysics letters ; an international journal of biophysics N2 - The enzyme diisopropyl fluorophosphatase (DFPase) from the squid Loligo vulgaris is of great interest because of its ability to catalyze the hydrolysis of highly toxic organophosphates. In this work, the enzyme structure in solution (native state) was studied by use of different scattering methods. The results are compared with those from hydrodynamic model calculations based on the DFPase crystal structure. Bicontinuous microemulsions made of sugar surfactants are discussed as host systems for the DFPase. The microemulsion remains stable in the presence of the enzyme, which is shown by means of scattering experiments. Moreover, activity assays reveal that the DFPase still has high activity in this complex reaction medium. To complement the scattering experiments cryo-SEM was also employed to study the microemulsion structure. KW - Dynamic light scattering KW - Neutron spin echo KW - Microemulsion KW - Enzyme catalysis KW - SANS KW - Protein structure Y1 - 2011 U6 - https://doi.org/10.1007/s00249-011-0689-0 SN - 0175-7571 VL - 40 IS - 6 SP - 761 EP - 774 PB - Springer CY - New York ER - TY - JOUR A1 - Koeth, Anja A1 - Tiersch, Brigitte A1 - Appelhans, Dietmar A1 - Gradzielski, Michael A1 - Cölfen, Helmut A1 - Koetz, Joachim T1 - Synthesis of Core-Shell Gold Nanoparticles with Maltose-Modified Poly(Ethyleneimine) JF - Journal of dispersion science and technology N2 - The synthesis of ultrafine gold nanoparticles in presence of maltose-modified hyperbranched poly(ethyleneimines) (PEI) is described. The polymer acted as both a reducing and stabilising agent in the particle formation process. The nanoparticles were characterized by means of dynamic light scattering (DLS), transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), small-angle x-ray scattering (SAXS), and small-angle neutron scattering (SANS). The mechanism of nanoparticle formation can be described in two steps. The reduction process of the Au3+ ions located in the inner coil region of the hyperbranched PEI led to the formation of a compact gold core, and is accompanied by a collapse of the polymer coil. Therefore, in the subsequent reduction process a gold-polymer hybrid shell is formed. By using the PEI of higher molar mass, core-shell gold nanoparticles of about 3.6 nm size with a more narrow size distribution and special fluorescence behavior could be synthesized. KW - Gold nanoparticles KW - gold-polymer hybrid shell KW - maltose-modified poly(ethyleneimine) Y1 - 2012 U6 - https://doi.org/10.1080/01932691.2010.530084 SN - 0193-2691 VL - 33 IS - 1-3 SP - 52 EP - 60 PB - Taylor & Francis Group CY - Philadelphia ER - TY - JOUR A1 - Bechthold, Nina A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Friberg, Stig E. T1 - Structure Formation in polymer-modified liquid crystals Y1 - 1999 ER - TY - JOUR A1 - Rojas, Oscar A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Tiersch, Brigitte A1 - Wacker, Philipp A1 - Kramer, Markus T1 - Structural studies of ionic liquid-modified microemulsions N2 - This work is focused on the influence of an ionic liquid (IL), i.e. ethyl-methylimidazolium hexylsulfate, on the spontaneous formation of microemulsions with ionic surfactants. The influence of the ionic liquid on Structure formation in the optically clear phase region in water/toluene/pentanol mixtures in presence of the cationic surfactant CTAB was studied in more detail. The results show a significant increase of the transparent phase region by adding the ionic liquid. Conductometric investigations demonstrate that adding the ionic liquid can drastically reduce the droplet- droplet interactions in the L-2 phase. H-1 nuclear magnetic resonance (H-1 NMR) diffusion coefficient measurements in combination with dynamic light scattering measurements clearly show that inverse microemulsion droplets still exist, but the droplet size is decreased to 2 nm. A more detailed characterisation of the isotropic phase channel by means of conductivity measurements, dynamic light scattering (DLS), H-1 NMR and cryo-scanning electron microscopy (SEM), allows the identification of a bicontinuous sponge phase between the L-1 and L-2 phase. When the poly(ethyleneimine) is added, the isotropic phase range is reduced drastically, but the inverse microemulsion range still exists. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00219797 U6 - https://doi.org/10.1016/j.jcis.2009.02.039 SN - 0021-9797 ER - TY - JOUR A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Hartmann, Jürgen T1 - Structural Analysis of the influence of polymers on lyotropic liquid-crystal systems Y1 - 1997 ER - TY - JOUR A1 - Rusu, Viorel Marin A1 - Ng, C. H. A1 - Wilke, Max A1 - Tiersch, Brigitte A1 - Fratzl, Peter A1 - Peter, Martin G. T1 - Size-controlled hydroxyapatite nanoparticles as self-organized organic-in organic composite materials N2 - This paper presents some results concerning the size-controlled hydroxyapatite nanoparticles obtained in aqueous media in a biopolymer matrix from soluble precursors salts. Taking the inspiration from nature, where composite materials made of a polymer matrix and inorganic fillers are often found, e.g. bone, shell of crustaceans, shell of eggs, etc., the feasibility on making composite materials containing chitosan and nanosized hydroxyapatite was investigated. A stepwise co-precipitation approach was used to obtain different types of composites by means of different ratio between components. The synthesis of hydroxyapatite was carried out in the chitosan matrix from calcium chloride and sodium dihydrogenphosphate in alkaline solutions at moderate pH of 10-11 for 24 h. Our research is focused on studying and understanding the structure of this class of composites, aiming at the development of novel materials, controlled at the nanolevel scale. The X-ray diffraction technique was employed in order to study the kinetic of hydroxyapatite formation in the chitosan matrix as well as to determine the HAp crystallite sizes in the composite samples. The hydroxyapatite synthesized using this route was found to be nano-sized (15-50nm). Moreover, applying an original approach to analyze the (002) XRD diffraction peak profile of hydroxyapatite by using a sum of two Gauss functions, the bimodal distribution of nanosized hydroxyapatite within the chitosan matrix was revealed. Two types of size distribution domains such as cluster-like (between 200 and 400 nm), which are the habitat of "small" hydroxyapatite nanocrystallites and scattered-like, which are the habitat of "large" hydroxyapatite nanocrystallites was probed by TEM and CSLM. The structural features of composites suggest that self-assembly processes might be involved. The composites contain nanosized hydroxyapatite with structural features close to those of biological apatites that make them attractive for bone tissue engineering applications. (c) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0142-9612 ER - TY - JOUR A1 - Großkopf, Sören A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Mix, Andreas A1 - Hellweg, Thomas T1 - Shear-Induced Transformation of Polymer-Rich Lamellar Phases to Micron-Sized Vesicles JF - Langmuir N2 - In the present work, we study the shear-induced transformation of polymer-rich lamellar phases into vesicles. The evolution of vesicle size is studied by different scattering techniques, rheology, and microscopy methods. The lamellar phase found in the system D2O/o-xylene/Pluronic PE9400/C(8)TAB can be fully transformed to multilamellar vesicles (MLVs) by applying shear. The size of the MLVs is proportional to the inverse square root of the shear rate. Hence, the polymer based quaternary system behaves similar to lamellar phases based on small surfactant molecules. Additionally, we found a growth effect leading to a size increase of the vesicles after shearing was stopped. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.8602786 SN - 0743-7463 VL - 35 IS - 8 SP - 3048 EP - 3057 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Koetz, Joachim A1 - Beitz, Toralf A1 - Tiersch, Brigitte T1 - Self assembled polymer-surfactant systems Y1 - 1999 ER - TY - JOUR A1 - Navarro, Salvador A1 - Shkilnyy, Andriy A1 - Tiersch, Brigitte A1 - Taubert, Andreas A1 - Menzel, Henning T1 - Preparation, characterization, and thermal gelation of amphiphilic alkyl-poly(ethyleneimine) N2 - Amphiphilic alkyl-poly(ethyleneimine)s (alkyl-PEI) with different degrees of polymerization have been produced by alkaline hydrolysis of alkyl-poly(2-methyl-2-oxazoline). Potentiometric titration of the alkyl-PEI shows the influence of the alkyl chain and the degree of polymerization on the titration curves and hence on the polymer conformation. Karl Fischer titration has been used to determine the water content in the polymers. Subsequent X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) measurements prove the existence of different hydration states of the PEI even under dry storage conditions. Upon cooling from hot aqueous Solutions, hydrogels form. The gelation concentration decreases with increasing degree of polymerization of the PEI segment. Scanning electron microscopy (SEM and cryo-SEM) of the hydrogels reveal an alkyl-PEI fibrous network composed of fan-like units. DSC shows that the percentages of bound and free water in the hydrogels depend on the concentration of polar amino groups. Y1 - 2009 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La9013569 SN - 0743-7463 ER - TY - JOUR A1 - Wegener, Michael A1 - Wirges, Werner A1 - Tiersch, Brigitte T1 - Porous polytetrafluoroethylene (PTFE) electret films : porosity and time dependent charging behaviour of the free surface N2 - Electrically charged porous polytetrafluoroethylene (PTFE) films are often discussed as active layers for electromechanical transducers. Here, the electric charging behavior of open-porous PTFE films with different porosities is investigated. Optimized electric charging of porous PTFE films is determined by variation of charging parameters such as electric fields and charging times. Maximum surface potentials are depending on the porosity of the PTFE films. Suitable charging leads to high surface potentials observed on non-stretched or slightly stretched porous PTFE films. Further increase of charging fields yields decreasing values of the surface potential accompanied with an increase of conductivity. Y1 - 2006 UR - http://www.springerlink.com/content/601u86x365560515/ U6 - https://doi.org/10.1007/s10934-006-9015-0 ER - TY - JOUR A1 - Koetz, Joachim A1 - Beitz, Toralf A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - Polymer-modified microemulsions Y1 - 2000 ER - TY - JOUR A1 - Lutter, Stefanie A1 - Koetz, Joachim A1 - Tiersch, Brigitte A1 - Kosmella, Sabine T1 - Polymer-modified bicontinuous microemulsions used as a template for the formation of nanorods N2 - This article is focused on the characterization of the poly(ethylene glycol) (PEG)-induced bicontinuous microemulsion of the pseudo-ternary system sodium dodecylsulfate (SDS)/xylene-pentanol/water by means of differential scanning calorimetry, rheology, and conductometry. The influence of the polymer concentration (cp) and the molecular weight (Mw) on the microstructure of the microemulsion was investigated using Cryo scanning electron microscopy. It was found that an increase of cp influences the structure of the sponge-like phase significantly. These polymer-modified microemulsions can be used as a template phase for the formation of BaSO4 nanorods, where individual nanoparticles (5nm in size) are ordered along the polymer backbone. Y1 - 2009 UR - http://www.informaworld.com/openurl?genre=journal&issn=0193-2691 U6 - https://doi.org/10.1080/01932690802643113 SN - 0193-2691 ER - TY - JOUR A1 - Robertson, Daniela A1 - Hellweg, Thomas A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Polymer-induced structural changes in lecithin/sodium dodecyl sulfate-based multilamellar vesicles N2 - Aqueous concentrated lecithin mixtures (asolectin from soybean) show typical lamellar liquid crystalline behavior and the individual lamellae tend to form spherical supramolecular structures, i.e., multilamellar vesicles. When part of the lecithin is replaced by the anionic surfactant sodium dodecyl sulfate (SIDS), the compact multilamellar vesicles disappear and the viscosity decreases. By adding oly(diallyldimethylammonium chloride) (PDADMAC) to the lecithin/SDS system, the formation of multilamellar vesicles can be induced again and the viscosity increases. However, one characteristic feature of these polymer-modified systems is a temperature-dependent phase transition from a compact multilamellar vesicle phase to a more swollen liquid crystalline phase. The polymer-modified multilamellar compact vesicles are of interest for utilization as new thermosensitive drug delivery systems. (C) 2003 Elsevier Inc. All rights reserved Y1 - 2004 SN - 0021-9797 ER - TY - JOUR A1 - Robertson, Daniela A1 - Hellweg, Thomas A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Polymer induced structural changes in lecithin/SDS-based multilamellar vesicles Y1 - 2004 SN - 0021-9797 ER - TY - JOUR A1 - Koetz, Joachim A1 - Bahnemann, Jennifa A1 - Lucas, Gordon A1 - Tiersch, Brigitte A1 - Kosmella, Sabine T1 - Polyelectrolyte-modified microemulsions as new templates for the formation of nanoparticles N2 - The paper is focused on the formation and redispersion of monodisperse BaSO4 nanoparticles in polyelectrolyte- modified microemulsions. It is shown that a cationic polyelectrolyte of low molar mass, e.g. poly(dially1dimethylammonium chloride) (PDADMAC), can be incorporated into the individual inverse microemulsion droplets (L2 phase) consisting of heptanol, water, and an amphoteric surfactant with a sulfobetaine head group. These PDADMAC- filled microemulsion droplets can be successfully used as a template phase for the nanoparticle formation. The monodisperse BaSO4 nanoparticles are produced by a simple mixing procedure and can be redispersed after solvent evaporation without a change in particle dimensions. Dynamic and electrophoretical light scattering in combination with sedimentation experiments in the analytical Ultracentrifuge of the redispersed powder show polyelectrolyte-stabilized nanoparticles with diameters of about 6 nm. The polyelectrolyte shows a "size control effect", which can be explained by the polyelectrolyte-surfactant interactions in relation to the polyelectrolyte-nanoparticle interactions during the particle growth, solvent evaporation and redispersion process. However, the approach used here opens away to produce different types of polyelectrolyte-stabilized nanoparticles (including rare metals, semiconductors, carbonates or oxides) of very small dimensions. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0927-7757 ER - TY - JOUR A1 - Koetz, Joachim A1 - Tiersch, Brigitte A1 - Bogen, Iris T1 - Polyelectrolyte induced vesicle-formation in lamellar liquid crystalline model systems Y1 - 2000 ER -