@article{SchueringsNevskyiEliaschetal.2016, author = {Sch{\"u}rings, Marco-Philipp and Nevskyi, Oleksii and Eliasch, Kamill and Michel, Ann-Katrin and Liu, Bing and Pich, Andrij and B{\"o}ker, Alexander and von Plessen, Gero and W{\"o}ll, Dominik}, title = {Diffusive Motion of Linear Microgel Assemblies in Solution}, series = {Polymers}, volume = {8}, journal = {Polymers}, publisher = {MDPI}, address = {Basel}, issn = {2073-4360}, doi = {10.3390/polym8120413}, pages = {14}, year = {2016}, abstract = {Due to the ability of microgels to rapidly contract and expand in response to external stimuli, assemblies of interconnected microgels are promising for actuation applications, e.g., as contracting fibers for artificial muscles. Among the properties determining the suitability of microgel assemblies for actuation are mechanical parameters such as bending stiffness and mobility. Here, we study the properties of linear, one-dimensional chains of poly(N-vinylcaprolactam) microgels dispersed in water. They were fabricated by utilizing wrinkled surfaces as templates and UV-cross-linking the microgels. We image the shapes of the chains on surfaces and in solution using atomic force microscopy (AFM) and fluorescence microscopy, respectively. In solution, the chains are observed to execute translational and rotational diffusive motions. Evaluation of the motions yields translational and rotational diffusion coefficients and, from the translational diffusion coefficient, the chain mobility. The microgel chains show no perceptible bending, which yields a lower limit on their bending stiffness.}, language = {en} } @misc{RajuLiebigHessetal.2019, author = {Raju, Rajarshi Roy and Liebig, Ferenc and Hess, Andreas and Schlaad, Helmut and Koetz, Joachim}, title = {Temperature-triggered reversible breakdown of polymer-stabilized olive}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {751}, issn = {1866-8372}, doi = {10.25932/publishup-43646}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436461}, pages = {19271 -- 19277}, year = {2019}, abstract = {A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol\% oleoyl side chains. Completely engulfed emulsion droplets remained stable at room temperature and could be destabilized on demand upon heating to the transition temperature of the polymeric stabilizer. Time-dependent light micrographs demonstrate the temperature-induced breakdown of the Janus droplets, which opens new aspects of application, for instance in biocatalysis.}, language = {en} } @article{RajuLiebigHessetal.2019, author = {Raju, Rajarshi Roy and Liebig, Ferenc and Hess, Andreas and Schlaad, Helmut and Koetz, Joachim}, title = {Temperature-triggered reversible breakdown of polymer-stabilized olive}, series = {RSC Advances}, volume = {9}, journal = {RSC Advances}, number = {35}, publisher = {RSC Publishing}, address = {London}, issn = {2046-2069}, doi = {10.1039/c9ra03463c}, pages = {19271 -- 19277}, year = {2019}, abstract = {A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol\% oleoyl side chains. Completely engulfed emulsion droplets remained stable at room temperature and could be destabilized on demand upon heating to the transition temperature of the polymeric stabilizer. Time-dependent light micrographs demonstrate the temperature-induced breakdown of the Janus droplets, which opens new aspects of application, for instance in biocatalysis.}, language = {en} } @article{VukicevicNeffeLuetzowetal.2015, author = {Vukicevic, Radovan and Neffe, Axel T. and Luetzow, Karola and Pierce, Benjamin F. and Lendlein, Andreas}, title = {Conditional Ultrasound Sensitivity of Poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] Microgels for Controlled Lipase Release}, series = {Macromolecular rapid communications}, volume = {36}, journal = {Macromolecular rapid communications}, number = {21}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201500311}, pages = {1891 -- 1896}, year = {2015}, abstract = {Triggering the release of cargo from a polymer network by ultrasonication as an external, non-invasive stimulus can be an interesting concept for on-demand release. Here, it is shown that, in pH-and thermosensitive microgels, the ultrasound sensitivity of the polymer network depends on the external conditions. Crosslinked poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] microgels showed a volume phase transition temperature (VPTT) of 25-50 degrees C, which increases with decreasing pH. Above the VPTT the polymer chains are collapsed, while below VPTT they are extended. Only in the case of maximum observed swelling, where the polymer chains are expanded, the microgels are mechanically fragmented through ultrasonication. In contrast, when the polymer chains are partially collapsed it is not possible to manipulate the microgels by ultrasound. Additionally, the ultrasound-induced on-demand release of wheat germ lipase from the microgels could be demonstrated successfully. The principle of conditional ultrasound sensitivity is likely to be general and can be used for selection of matrix-cargo combinations.}, language = {en} } @phdthesis{Leiendecker2016, author = {Leiendecker, Mai-Thi}, title = {Physikalische Hydrogele auf Polyurethan-Basis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-103917}, school = {Universit{\"a}t Potsdam}, pages = {109}, year = {2016}, abstract = {Physical hydrogels have gained recent attention as cell substrates, since viscoelasticity or stress relaxation is a powerful parameter in mechanotransduction, which has long been neglected. We designed multi-functional polyurethanes to form physical hydrogels via a unique tunable gelation mechanism. The anionic polyurethanes spontaneously form aggregates in water that are kept in a soluble state through electrostatic repulsion. Fast subsequent gelation can be triggered by charge shielding which allows the aggregation and network building to proceed. This can be induced by adding either acids or salts, resulting in acidic (pH 4-5) or pH-neutral hydrogels, respectively. Whereas conventional polyurethane-based hydrogels are commonly prepared from toxic isocyanate precursors, the physical hydrogelation mechanism described here does not involve chemically reactive species which is ideal for in situ applications in sensitive environments. Both stiffness and stress relaxation can be tuned independently over a broad range and the gels exhibit excellent stress recovery behavior.}, language = {de} }