| Hörsaal A1
Prof. Dr. Thomas Hellweg
Gemeinsames Physikalisch- Chemisches Kolloquium
Smart microgels and microgel nanoparticle hybrids: Properties, characterization, and potential applications
Microgels based on poly(N-isopropylacrylamide) (PNIPAM) belong to the class of so called smart materials, which are able to respond upon changes of an external parameter like e.g. temperature by changes in particle dimensions. This talk will briefly review the properties of these materials including characterization by (cryo-)TEM and scattering experiments.
An interesting application of such colloids is the preparation of monolayer films from these particles [1,2]. Microgels are non-covalently attached to a surface allowing us to use them on a broad variety of (charged) surfaces. This is a major advantage as compared to approaches relying on covalent attachment of active films. The shape of the coated substrate shouldn't be of importance.
Such thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed vertebrate cells via simply changing the temperature. Cell response occurs on the timescale of several minutes, is reversible, and allows to harvest vertebrate cells in a mild fashion . Also free- standing membranes can be prepared from such microgel based surface coatings. Moreover, to create interesting optical properties responsive microgels can be combined with nanoparticles . Also examples for such hybrid systems will be discussed (e.g. ).
 Schmidt, S., H. Motschmann, T. Hellweg, and R. von Klitzing: Thermoresponsive surfaces by spin-coating of PNIPAM-co-PAA microgels. A combined AFM and ellipsometry study. POLYMER, 49: 749-756, 2008
 Schmidt, S., T. Hellweg, and R. von Klitzing: Control of the packing density of P(NIPAM-co-AA) microgel films: Effect of surface charge, pH, and preparation technique. Langmuir, 24: 12595-12602, 2008.
 Schmidt, S.,M. Zeiser, Th. Hellweg, C. Duschl, A. Fery, and H. Möhwald: Adhesion and Mechanical Properties of PNIPAM Microgel Films and their Potential Use as Switchable Cell Culture Substrates. Adv. Func. Mater., 20:3235–3243, 2010.  Hellweg, T.: Responsive Core-Shell Microgels: Synthesis, Characterization, and possible Applications. J. Polymer Sci., Part B Polymer Physics, 51:1073-1083, 2013  Karg, M., T. Hellweg, P. Mulvaney: Self-Assembly of Tunable Nanocrystal Superlattices Using Poly-(NIPAM) Spacers, Adv. Func. Mater., 21:4668-4676, 2011
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