Thomas Hellweg currently works at the Faculty of Chemistry, Dep. of Physical and Biophysical Chemistry, Bielefeld University. Thomas does research in Physical Chemistry and Materials Science with a focus on "Soft Matter". One of the current projects of the Hellweg group is 'Smart core-shell microgels as nanoparticle carriers for catalysis.' Another important current project is the study of saponins and their interaction with lipid bilayers. The group uses mainly scattering experiments (light, X-rays, and neutrons) complemented by high resolution imaging techniques (cryogenic transmission electron microscopy (Cryo-TEM), scanning force microscopy, scanning electron microcopy (SEM), and different optical microscopy techniques. In addition all standard techniques to study colloids are used.
When: Tuesday, August 27, at 09.00
Where: LINXS Workshop room, Ideon Delta 5, Scheelevägen 19, 5th floor (map)
Title: Smart microgels studied by intelligent use of neutron scattering
Smart microgels are studied since 1986 and the yearly number of articles especially on N-isopropylacrylamide (NIPAM) based systems reaches 500 meanwhile. However, recently also other acrylamides came into focus. All these microgels exhibit a so-called volume phase transition at the lower critical solution temperature of the respective polymer and can therefore be used as actuators or sensors in mesoscale devices. The properties of microgels were reviewed recently . A full understanding of these colloidal materials can only be achieved using scattering experiments and especially neutron scattering techniques are very useful due to the possibility of contrast variation by full or partial deuteration. Moreover, the time and length scale of e.g. network dynamics lies well in the range of quasi-elastic neutron scattering techniques like neutron spin-echo (NSE).
The talk will summarize our contributions to the study of smart microgels by small angle neutron scattering and NSE. The focus will be on studies of the structure of core-shell microgels (collaboration with Julian Oberdisse)  and on the determination of the response times of such colloidal gels (collaboration with Thomas Sottmann) . However, also some recent time resolved neutron reflectometry data will be presented (collaboration with the groups of Peter Müller-Buschbaum and Regine von Klitzing) .
 M. Karg et al. Langmuir 2019, 35, 6231
 M. Cors, L. Wiehemeier,Y. Hertle, A. Feoktystov, F. Cousin, T. Hellweg, J. Oberdisse; Langmuir, 2018, 34 (50), 15403.
 O. Wrede et al. Scientific Reports, 2018, 8, 13781.