TY - JOUR A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Klemke, Bastian A1 - Koetz, Joachim T1 - pH-responsive magnetic Pickering Janus emulsions JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - We report ultrasonically generated pH-responsive Pickering Janus emulsions of olive oil and silicone oil with controllable droplet size and engulfment. Chitosan was used as a pH-responsive emulsifier. The increase of pH from 2 to 6 leads to a transition from completely engulfed double emulsion droplets to dumbbell-shaped Janus droplets accompanied by a significant decrease of droplet diameter and a more homogeneous size distribution. The results can be elucidated by the conformational change of chitosan from a more extended form at pH 2 to a more flexible form at pH 4-5. Magnetic responsiveness to the emulsion was attributed by dispersing superparamagnetic nanoparticles (Fe3O4 with diameter of 13 +/- 2 nm) in the olive oil phase before preparing the Janus emulsion. Incorporation of magnetic nanoparticles leads to superior emulsion stability, drastically reduced droplet diameters, and opened the way to control movement and orientation of the Janus droplets according to an external magnetic field. KW - Janus emulsion KW - Chitosan KW - pH-responsive KW - Magnetic-responsive KW - Cryo-SEM KW - TEM Y1 - 2018 U6 - https://doi.org/10.1007/s00396-018-4321-z SN - 0303-402X SN - 1435-1536 VL - 296 IS - 6 SP - 1039 EP - 1046 PB - Springer CY - New York 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 - Schulze, Nicole A1 - Appelhans, D. A1 - Tiersch, Brigitte A1 - Koetz, Joachim T1 - Morphological transformation of vesicles into tubular structures by adding polyampholytes or dendritic glycopolymers JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - For the first time tubulating properties of spherical dendritic glycopolymers and linear alternating polyampholytes against non-uniform negatively charged giant vesicles are proven by light microscopy and cryo-scanning electron microscopy study. Real time observation of the morphological transformation from giant vesicles to tubular structures, simulating morphogenesis in living cells, is given by using the cationic and H-bond active dendritic glycopolymer accompanied by reducing the size of the giant vesicles and the evidence of vesicle-vesicle interaction which was only postulated in a previous study. Similar morphogenesis of non-uniform giant vesicles into tubular network structure can be observed by using a polyampholyte in the stretched conformation at pH 9. Pearl necklace and tubular network structure formation are also observed by applying anionic vesicles of significant smaller dimensions with average size dimensions of 35 nm, after adding the polyampholyte at pH 9. However, the fitting accuracy between the functional groups along the backbone chain of the polyampholyte on one side and the vesicle surface on the other side is of high importance for the transformation process by using polyampholytes. The resulting tubular and network structures offer new fields of application as microfluidic transport channels or template phases for the shape controlled formation of nanoparticles. (C) 2014 Elsevier B.V. All rights reserved. KW - Alternating polyampholytes KW - Maltose-modified PEI KW - Network structure KW - Template phase KW - Cryo-SEM KW - DLS Y1 - 2014 U6 - https://doi.org/10.1016/j.colsurfa.2014.06.007 SN - 0927-7757 SN - 1873-4359 VL - 457 SP - 326 EP - 332 PB - Elsevier CY - Amsterdam ER -