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 - Beisebekov, Madiar Maratovich A1 - Serikpayeva, Saniya B. A1 - Zhumagalieva, Shynar Nurlanovna A1 - Beisebekov, Marat Kianovich A1 - Abilov, Zharylkasyn Abduachitovich A1 - Kosmella, Sabine A1 - Koetz, Joachim T1 - Interactions of bentonite clay in composite gels of non-ionic polymers with cationic surfactants and heavy metal ions JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - Chemically cross-linked composite gels based on bentonite clay from Manyrak deposit (Kazakhstan Republic) and nonionic polymers, i.e., poly(hydroxyethylacrylate) and poly(acrylamide), were polymerized in situ after preliminary intercalation of monomers in an aqueous suspension of bentonite clay. By means of cryo-scanning electron microscopy, it was shown that bentonite clay is well incorporated into the gel network structure with pore sizes up to 1.5 mu m. The intercalated bentonite clay can adsorb cationic surfactants as well as heavy metal ions due to electrostatic interactions. Conductometric and surface tension measurements indicate not only the adsorption of surfactants and heavy metals inside the hydrogel, but also the displacement of the critical micellization concentration (CMC) of the surfactants. KW - Bentonite clay KW - Cationic surfactants KW - Heavy metal ions KW - Composite hydrogels Y1 - 2015 U6 - https://doi.org/10.1007/s00396-014-3463-x SN - 0303-402X SN - 1435-1536 VL - 293 IS - 2 SP - 633 EP - 639 PB - Springer CY - New York ER - TY - JOUR A1 - Beitz, Toralf A1 - Koetz, Joachim A1 - Friberg, Stig E. T1 - Polymer-modified ionic microemulsion formed in the system SDS/Water/Xylene/Pentanol Y1 - 1999 ER - TY - JOUR A1 - Beitz, Toralf A1 - Koetz, Joachim A1 - Wolf, Gunter A1 - Kleinpeter, Erich A1 - Friberg, Stig E. T1 - Poly(N-vinyl-2-pyrrolidone) and 1-octyl-2-pyrrolidinone modified ionic microemulsions Y1 - 2001 ER - TY - JOUR A1 - Bertz, Andreas A1 - Wöhl-Bruhn, Stefanie A1 - Miethe, Sebastian A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Hust, Michael A1 - Bunjes, Heike A1 - Menzel, Henning T1 - Encapsulation of proteins in hydrogel carrier systems for controlled drug delivery influence of network structure and drug size on release rate JF - Journal of biotechnology N2 - Novel hydrogels based on hydroxyethyl starch modified with polyethylene glycol methacrylate (HES-P(EG)(6)MA) were developed as delivery system for the controlled release of proteins. Since the drug release behavior is supposed to be related to the pore structure of the hydrogel network the pore sizes were determined by cryo-SEM, which is a mild technique for imaging on a nanometer scale. The results showed a decreasing pore size and an increase in pore homogeneity with increasing polymer concentration. Furthermore, the mesh sizes of the hydrogels were calculated based on swelling data. Pore and mesh size were significantly different which indicates that both structures are present in the hydrogel. The resulting structural model was correlated with release data for bulk hydrogel cylinders loaded with FITC-dextran and hydrogel microspheres loaded with FITC-IgG and FITC-dextran of different molecular size. The initial release depended much on the relation between hydrodynamic diameter and pore size while the long term release of the incorporated substances was predominantly controlled by degradation of the network of the much smaller meshes. KW - Hydrogel KW - Hydrogel microspheres KW - Network structure KW - Release studies KW - Protein delivery KW - Mesh size Y1 - 2013 U6 - https://doi.org/10.1016/j.jbiotec.2012.06.036 SN - 0168-1656 VL - 163 IS - 2 SP - 243 EP - 249 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Beyermann, Jochen A1 - Koetz, Joachim A1 - Jäger, Werner A1 - Friberg, Stig E. T1 - Influence of charge density of anionic polyelectrolytes on structure formation in liquid crystalline systems Y1 - 1999 ER - TY - JOUR A1 - Bogomolova, Anna A1 - Secker, Christian A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Thermo-induced multistep assembly of double-hydrophilic block copolypeptoids in water JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - The aqueous solution behavior of thermoresponsive-hydrophilic block copolypeptoids, i.e., poly(N-(n-propyl)glycine) (x) -block-poly(N-methylglycine) (y) (x = 70; y = 23, 42, 76), in the temperature range of 20-45 A degrees C is studied. Turbidimetric analyses of the 0.1 wt% aqueous solutions reveal two cloud points at T (cp)similar to 30 and 45 A degrees C and a clearing point in between at T (cl)similar to 42 A degrees C. Temperature-dependent dynamic light scattering (DLS) suggest that right above the first collapse temperature, single polymer molecules assemble into large structures which upon further heating, i.e., at the clearing point temperature, disassemble into micelle-like structures. Upon further heating, the aggregates start to grow again in size, as recognized by the second cloud point, through a crystallization process. KW - Polypeptoids KW - Block copolymers KW - Thermoresponsive KW - Self-assembly Y1 - 2017 U6 - https://doi.org/10.1007/s00396-017-4044-6 SN - 0303-402X SN - 1435-1536 VL - 295 SP - 1305 EP - 1312 PB - Springer CY - New York ER - TY - JOUR A1 - Bourgat, Yannick A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Menzel, Henning T1 - Enzyme degradable polymersomes from chitosan-g-[poly-l-lysine-block-epsilon-caprolactone] copolymer JF - Macromolecular bioscience N2 - The scope of this study includes the synthesis of chitosan-g-[peptide-poly-epsilon-caprolactone] and its self-assembly into polymeric vesicles employing the solvent shift method. In this way, well-defined core-shell structures suitable for encapsulation of drugs are generated. The hydrophobic polycaprolactone side-chain and the hydrophilic chitosan backbone are linked via an enzyme-cleavable peptide. The synthetic route involves the functionalization of chitosan with maleimide groups and the preparation of polycaprolactone with alkyne end-groups. A peptide functionalized with a thiol group on one side and an azide group on the other side is prepared. Thiol-ene click-chemistry and azide-alkyne Huisgen cycloaddition are then used to link the chitosan and poly-epsilon-caprolactone chains, respectively, with this peptide. For a preliminary study, poly-l-lysin is a readily available and cleavable peptide that is introduced to investigate the feasibility of the system. The size and shape of the polymersomes are studied by dynamic light scattering and cryo-scanning electron microscopy. Furthermore, degradability is studied by incubating the polymersomes with two enzymes, trypsin and chitosanase. A dispersion of polymersomes is used to coat titanium plates and to further test the stability against enzymatic degradation. KW - chitosan KW - click chemistry KW - drug delivery system KW - enzyme KW - polymersomes KW - poly‐ ε ‐ caprolactone Y1 - 2020 U6 - https://doi.org/10.1002/mabi.202000259 SN - 1616-5187 SN - 1616-5195 VL - 21 IS - 1 SP - 1 EP - 9 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Bourgat, Yannick A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Menzel, Henning T1 - Enzyme degradable polymersomes from chitosan-g-[poly-l-lysine-block-epsilon-caprolactone] copolymer T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The scope of this study includes the synthesis of chitosan-g-[peptide-poly-epsilon-caprolactone] and its self-assembly into polymeric vesicles employing the solvent shift method. In this way, well-defined core-shell structures suitable for encapsulation of drugs are generated. The hydrophobic polycaprolactone side-chain and the hydrophilic chitosan backbone are linked via an enzyme-cleavable peptide. The synthetic route involves the functionalization of chitosan with maleimide groups and the preparation of polycaprolactone with alkyne end-groups. A peptide functionalized with a thiol group on one side and an azide group on the other side is prepared. Thiol-ene click-chemistry and azide-alkyne Huisgen cycloaddition are then used to link the chitosan and poly-epsilon-caprolactone chains, respectively, with this peptide. For a preliminary study, poly-l-lysin is a readily available and cleavable peptide that is introduced to investigate the feasibility of the system. The size and shape of the polymersomes are studied by dynamic light scattering and cryo-scanning electron microscopy. Furthermore, degradability is studied by incubating the polymersomes with two enzymes, trypsin and chitosanase. A dispersion of polymersomes is used to coat titanium plates and to further test the stability against enzymatic degradation. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1382 KW - chitosan KW - click chemistry KW - drug delivery system KW - enzyme KW - polymersomes KW - poly‐ ε ‐ caprolactone Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-566584 SN - 1866-8372 IS - 1 ER - TY - JOUR A1 - Bressel, Katharina A1 - Prevost, Sylvain A1 - Appavou, Marie-Sousai A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Gradzielski, Michael T1 - Phase behaviour and structure of zwitanionic mixtures of perfluorocarboxylates and tetradecyldimethylamine oxide-dependence on chain length of the perfluoro surfactant JF - Soft matter N2 - Phase behaviour and the mesoscopic structure of zwitanionic surfactant mixtures based on the zwitterionic tetradecyldimethylamine oxide (TDMAO) and anionic lithium perfluoroalkyl carboxylates have been investigated for various chain lengths of the perfluoro surfactant with an emphasis on spontaneously forming vesicles. These mixtures were studied at a constant total concentration of 50 mM and characterised by means of dynamic light scattering (DLS), electric conductivity, small-angle neutron scattering (SANS), viscosity, and cryo-scanning electron microscopy (Cryo-SEM). No vesicles are formed for relatively short perfluoro surfactants. The extension of the vesicle phase becomes substantially larger with increasing chain length of the perfluoro surfactant, while at the same time the size of these vesicles increases. Head group interactions in these systems play a central role in the ability to form vesicles, as already protonating 10 mol% of the TDMAO largely enhances the propensity for vesicle formation. The range of vesicle formation in the phase diagram is not only substantially enlarged but also extends to shorter perfluoro surfactants, where without protonation no vesicles would be formed. The size and polydispersity of the vesicles are related to the chain length of the perfluoro surfactant, the vesicles becoming smaller and more monodisperse with increasing perfluoro surfactant chain length. The ability of the mixed systems to form well-defined unilamellar vesicles accordingly can be controlled by the length of the alkyl chain of the perfluorinated surfactant and depends strongly on the charge conditions, which can be tuned easily by pH-variation. Y1 - 2011 U6 - https://doi.org/10.1039/c1sm05618b SN - 1744-683X VL - 7 IS - 23 SP - 11232 EP - 11242 PB - Royal Society of Chemistry CY - Cambridge ER -