TY - JOUR A1 - Note, Carine A1 - Koetz, Joachim A1 - Kosmella, Sabine T1 - Structural changes in poly(ethyleneimine) modified microemulsion JF - Journal of colloid and interface science N2 - The influence of branched poly(ethyleneimine) on the phase behavior of the system sodium dodecylsulfate/toluene-pentanol (1:1)/water has been studied. The isotropic microemulsions still exist when water is replaced with aqueous solutions of PEI (up to 30% in weight), but their stability is significantly influenced. From a polymer concentration of 20 wt%, the polymer enhances the solubilization of water in oil, changes the sign of the spontaneous curvature of the surfactant film, and induces an inversion of the microemulsion type from water-in-oil (L-2) to oil-in-water (L-1), by the formation of a bicontinuous channel. Further investigations show that the addition of polymer in the L-2 phase changes the droplet-droplet interactions as the conductivity drops and the percolation disappears. In the bicontinuous channel, higher viscosities can be detected, as well as a weak percolation followed by a steep increase of the conductivity, which can be related to evident structural changes in the system. DSC measurements allow then to follow the changes of the water properties in the system, from interfacial-water in the L-2 phase to free-water in the sponge-like phase. Finally, all the measurements performed permit to characterize the structural transitions in the system and to understand the role of the added polymer. KW - polyelectrolyte KW - microemulsion KW - bicontinuous phase Y1 - 2006 U6 - https://doi.org/10.1016/j.jcis.2006.06.071 SN - 0021-9797 VL - 302 SP - 662 EP - 668 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Raju, Rajarshi Roy A1 - Kosmella, Sabine A1 - Friberg, Stig E. A1 - Koetz, Joachim T1 - Pickering Janus emulsions and polyelectrolyte complex-stabilized Janus gels JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Janus emulsions, containing olive oil (OO) and silicone oil (SiO), were formed in presence of polyelectrolyte complex particles, i.e., gelatin-sodium polyacrylate (NaPAA) complexes. The diameter of completely engulfed Janus droplets can be tuned between 50 and 200 mu m by varying the gelatin/NaPAA complex particle size between 200 and 400 nm. The gelatin/NaPAA complex particles adsorbed at the olive oil interface decrease the interfacial tension and stabilize the resulting completely engulfed Pickering Janus emulsions. Long-term stable Janus gels can be synthesized in presence of gelatin/sodium carboxymethylcellulose (NaCMC) mixtures. In that case Coulombic forces are of relevance with regard to the stabilization of the Janus droplets embedded in a gelatin/NaCMC gel matrix. Janus gels show elastic reological behavior and thixotropic properties. KW - Pickering Janus emulsions KW - Janus gels KW - Interfacial tension KW - Ring tensiometry KW - Gelatin-NaCMC KW - Gelatin-NaPAA composites Y1 - 2017 U6 - https://doi.org/10.1016/j.colsurfa.2017.08.022 SN - 0927-7757 SN - 1873-4359 VL - 533 SP - 241 EP - 248 PB - Elsevier CY - Amsterdam ER - TY - BOOK A1 - Koetz, Joachim A1 - Kosmella, Sabine T1 - Polyelectrolytes and nanoparticles T3 - Springer laboratory manuals in polymer science Y1 - 2007 SN - 3-540-46381-X PB - Springer-Verlag CY - Heidelberg ER - TY - JOUR A1 - Koetz, Joachim A1 - Bahnemann, Jennifa A1 - Kosmella, Sabine T1 - The influence of a cationic polyelectrolyte on the inverse micellar region of the ternary system sulfobetaine/ water/alcohol Y1 - 2004 UR - http://www3.interscience.wiley.com/cgi-bin/fulltext/106577728/PDFSTART SN - 0887-624X - ER - TY - JOUR A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Kulicke, Werner-Michael A1 - Heinze, Thomas T1 - Zum Einfluss des Lösungszustandes von Carboxymethylcellulosen auf das Strukturbildungsverhalten in kolloidalen Systemen Y1 - 2002 ER - TY - JOUR A1 - Koetz, Joachim A1 - Kosmella, Sabine T1 - Interactions of Polyelectrolytes with Clay Surfaces Y1 - 2002 SN - 0-8247-0633-1 ER - TY - JOUR A1 - Kosmella, Sabine A1 - Klemke, Bastian A1 - Häusler, Ines A1 - Koetz, Joachim T1 - From gel-like Pickering emulsions to highly ordered superparamagnetic magnetite aggregates with embedded gold nanoparticles JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Pickering emulsions with two types of nanoparticles, i.e., superparamagnetic magnetite nanoparticles dispersed in n-hexane and gold nanoparticles dispersed in water, were formed by rigorous mixing in presence of surface active polymeric surfactants. Monodisperse magnetite nanoparticles with a mean particle size of 4 nm were obtained by a microwave-assisted synthesis in n-hexane in presence of oleic acid, and gold nanoparticles were produced in aqueous solution in presence of the hyperbranched poly(ethyleneimine) (PEI) or sodium citrate as reducing and stabilizing agent. After mixing the prepared nanoparticle dispersions in presence of the Pluronics an intermediate gel-like phase is formed. The Pickering emulsion droplets in the intermediate phase are stabilized by both types of nanoparticles, as to be seen by cryo-SEM micrographs. After separating, solvent evaporation and redispersion in water highly ordered Pluronic-stabilized superparamagnetic magnetite nanoparticle aggregates with embedded gold nanoparticles can be obtained. KW - Pickering emulsions KW - Pluronics KW - Magnetite and gold nanoparticles KW - Ring tensiometry KW - Cryo-SEM KW - HRTEM KW - Magnetization measurements Y1 - 2019 U6 - https://doi.org/10.1016/j.colsurfa.2019.03.017 SN - 0927-7757 SN - 1873-4359 VL - 570 SP - 331 EP - 338 PB - Elsevier Science CY - Amsterdam ER - TY - JOUR A1 - Rumschöttel, Jens A1 - Baus, Susann A1 - Kosmella, Sabine A1 - Appelhans, Dietmar A1 - Koetz, Joachim T1 - Incorporation of DNA/PEI polyplexes into gelatin/chitosan hydrogel scaffolds BT - a mu-DSC study JF - Composite interfaces N2 - Polyplexes between a double-stranded Salmon DNA and hyperbranched poly(ethyleneimine) (PEI) as well as a maltosylated PEI-Mal were incorporated into a gelatin/chitosan hydrogel scaffold. Calorimetric experiments of the polyplexes show a decrease of the melting temperature in presence of PEI and a peak splitting in presence of PEI-Mal, which can be interpreted to a partial compaction of the DNA strands in presence of PEI-Mal. When the polyplexes are incorporated into a gelatin/chitosan scaffold in the swollen state, the DNA melting peaks at 90 and 93 degrees C, respectively, indicate in both cases the release of the DNA at the surface of the hydrogel scaffold in a more compact form. Specific interactions between the PEI-Mal shell and gelatin are responsible for the tuning of the release properties in presence of the maltose units in the hyperbranched PEI. KW - DNA-PEI polyplexes KW - maltosylated poly(ethyleneimine) KW - mu-DSC KW - DNA release KW - gelatin/chitosan hydrogel scaffold Y1 - 2017 U6 - https://doi.org/10.1080/09276440.2017.1302725 SN - 1568-5543 VL - 25 IS - 1 SP - 1 EP - 11 PB - Routledge, Taylor & Francis Group CY - Abingdon 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 - Dolya, Natalya A1 - Rojas, Oscar A1 - Kosmella, Sabine A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Kudaibergenov, Sarkyt T1 - "One-Pot" in situ frmation of Gold Nanoparticles within Poly(acrylamide) Hydrogels JF - Macromolecular chemistry and physics N2 - This paper focuses on two different strategies to incorporate gold nanoparticles (AuNPs) into the matrix of polyacrylamide (PAAm) hydrogels. Poly(ethyleneimine) (PEI) is used as both reducing and stabilizing agent for the formation of AuNPs. In addition, the influence of an ionic liquid (IL) (i.e., 1-ethyl-3-methylimidazolium ethylsulfate) on the stability of the nanoparticles and their immobilization in the hydrogel is investigated The results show that AuNPs surrounded by a shell containing PEI and IL, synthesized according to the one-pot approach, are much better immobilized within the PAAm hydrogel. Hereby, the IL is responsible for structural changes in the hydrogel as well as the improved stabilization and embedding of the AuNPs into the polymer gel matrix. KW - gold nanoparticles KW - immobilization KW - ionic liquids KW - poly(acrylamide) hydrogels Y1 - 2013 U6 - https://doi.org/10.1002/macp.201200727 SN - 1022-1352 VL - 214 IS - 10 SP - 1114 EP - 1121 PB - Wiley-VCH CY - Weinheim 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 - Andres, S. A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - BaSO4 nanorods produced in polymer-modified bicontinuous microemulsions N2 - The influence of the water soluble polymer poly(ethylene glycol) (PEG) on structure formation in the quasiternary system sodium dodecylsulfate (SDS)/pentanol-xylene/water was checked by means of conductometry, rheology, and micro differential calorimetry. The polymer induces the formation of an isotropic phase channel between the o/w and w/o microemulsion. The transition from the normal as well as from the inverse micellar to the bicontinuous phase range can be detected by conductometry, rheology as well as micro-DSC. As a result of polymer-surfactant interactions, the spontaneous curvature of the surfactant film is changed and a sponge phase is formed. The bicontinuous phase is characterized by a moderate shear viscosity, a Newtonian flow behaviour, and the disappearence of interphasal water in the heating curve of the micro-DSC. When the polymer-modified bicontinuous phase is used as a template phase for the nanoparticle formation, spherical BaSO4 nanoparticles were formed. During the following solvent evaporation process the primarily formed spherical nanoparticles aggregate to nanorods and triangular structures due to the non-restriction of the bicontinuous template phase in longitudinal direction Y1 - 2006 UR - http://www.ingentaconnect.com/content/vsp/ci U6 - https://doi.org/10.1163/156855406777408629 SN - 0927-6440 ER - TY - JOUR A1 - Note, Carine A1 - Koetz, Joachim A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - Hydrophobically modified polyelectrolytes used as reducing and stabilizing agent for the formation of gold nanoparticles N2 - This paper is focused on the synthesis and characterization of hydrophobically modified polyelectrolytes and their use as reducing as well as stabilizing agents for the formation of gold nanoparticles. Commercially available poly(acrylic acid) has been hydrophobically modified with various degrees of grafting of butylamine introduced randomly along the chain. Different analytical methods are performed, i.e., IR and H-1-NMR spectroscopy in combination with elemental analysis to determine the degree of grafting. The modified polymers can successfully be used for the controlled single-step synthesis and stabilization of gold nanoparticles. The process of nanoparticle formation is investigated by means of UV-vis spectroscopy. The size and shape of the particles obtained in the presence of unmodified or modified polyelectrolytes are characterized by dynamic light scattering, zeta potential measurements and transmission electron microscopy. The polyelectrolytes were involved in the crystallization process of the nanoparticles, and in the presence of hydrophobic microdomains at the particle surface, a better stabilization at higher temperature can be observed Y1 - 2005 SN - 0303-402X ER - TY - GEN A1 - Koetz, Joachim A1 - Reichelt, S. A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - Recovery of nanoparticles produced in phosphatidylcholine-based template phases N2 - This paper focuses on the characterization and use of polymer-modified phosphatidylcholine (PC)/sodium dodecyl sulfate (SDS)-based inverse microemulsions as a template phase for BaSO4 nanoparticle formation. The area of the optically clear inverse microemulsion phase in the isooctane/hexanol/water/PC/SDS system is not significantly changed by adding polyelectrolytes, i.e., poly(diallyldimethylammonium chloride) (PDADMAC), or amphoteric copolymers of diallyldimethylammonium chloride and maleamid acid to the SDS-modified inverse microemulsion. Shear experiments show non- Newtonian flow behavior and oscillation experiments show a frequency-dependent viscosity increase (dilatant behavior) of the microemulsions. Small amounts of bulk water were identified by means of differential scanning calorimetry. One can conclude that the macromolecules are incorporated into the individual droplets, and polymer-filled microemulsions are formed. The polymer-filled microemulsions were used as a template phase for the synthesis of BaSO4 nanoparticles. After solvent evaporation the nanoparticles were redispersed in water and isooctane, respectively. The polymers incorporated into the microemulsion are involved in the redispersion process and influence the size and shape of the redispersed BaSO4 particles in a specific way. The crystallization process mainly depends on the type of solvent and the polymer component added. In the presence of the cationic polyelectrolyte PDADMAC the crystallization to larger cubic crystals is inhibited, and layers consisting of polymer-stabilized spherical nanoparticles of BaSO4 (6 nm in size) will be observed. (c) 2004 Elsevier Inc. All rights reserved Y1 - 2005 SN - 0021-9797 ER - TY - JOUR A1 - Koetz, Joachim A1 - Brühl, Iris A1 - Kosmella, Sabine A1 - Reiche, Jürgen A1 - Tiersch, Brigitte T1 - Polyelectrolyte Complex Formation in Lamellar Liquid Crystalline Systems N2 - The influence of polyelectrolytes on structure formation in liquid crystalline Na-dodecylsulfate/decanol/water systems was investigated by means of small angle X-ray diffraction, rheology, NMR spectroscopy, and microscopy. By adding Na-polyacrylate (PAA) into the mesophase, the one-phase region is left and phenomena of phase separation into a solvent-rich and a polymer/surfactantrich phase occurs. By incoporating an anionic and cationic polyelectrolyte step by step the tendency of phase separation is increased drastically. The self-organization process can be regulated directly by varying the water content of the system. However, at a water content of 30% the properties of the resulting liquid crystal were changed drastically. X-ray diffraction shows a multitude of Bragg peaks, NMR shows a peak-splitting, and rheology shows a change from non-Newtonian to Newtonian-flow behavior. On the basis of the experimental results an ordered multilayer associate structure can be assumed. Y1 - 1997 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 - Koetz, Joachim A1 - Beitz, Toralf A1 - Kosmella, Sabine A1 - Tiersch, Brigitte T1 - Polymer-modified microemulsions Y1 - 2000 ER - TY - JOUR A1 - Koetz, Joachim A1 - Brühl, Iris A1 - Kosmella, Sabine T1 - Polyelektrolytkomplexbildung in lyotrop flüssigkristallinen Systemen Y1 - 1997 SN - 3-8265-2908-1 ER - TY - JOUR A1 - Kosmella, Sabine A1 - Koetz, Joachim A1 - Friberg, Stig E. A1 - Mackay, R. A T1 - Interactions of polyelectrolytes with the lyotropic liquid crystalline system Na-dodecylsulfate / decanol / water Y1 - 1996 ER - TY - JOUR A1 - Kosmella, Sabine A1 - Koetz, Joachim A1 - Friberg, Stig E. A1 - Mackay, R. A. T1 - Interactions of polyelectrolytes with the lyotropic liquid crystalline system - hexadecyltrimethylammonium bromide / decanol / water Y1 - 1996 SN - 0927-7757 ER -