Berlin 2018 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 51: Hydrogels and Microgels
CPP 51.4: Vortrag
Mittwoch, 14. März 2018, 15:45–16:00, C 264
Anomalous Dynamics of Concentrated Silica-PNIPAm Microgels — •Lara Frenzel1,2, Felix Lehmkühler1,2, Irina Lokteva1,2, Michael Sprung1, and Gerhard Grübel1,2 — 1DESY, Notkestr. 85, 22607 Hamburg — 2The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg
Poly(N-isopropylacrylamide) (PNIPAm) cross-linked microgels show a coil-to-globule transition in water at a lower critical solution temperature (LCST) around 32°C, below which the particles collapse drastically. With this volume phase transition PNIPAm is applicable in both technical as well as medical fields. It furthermore became a frequently studied system in soft matter research as a model system to probe the specific phase behavior of soft colloids. Via x-ray photon correlation spectroscopy (XPCS) we investigate the change of structure and dynamics of highly concentrated PNIPAm core-shell microgels around the LCST. Here we will present our work on particles with radii of 80-200 nm, whereby we investigated the dynamics and interaction of the highly concentrated colloids as a function of temperature. Upon heating from room temperature to 45°C we found three dynamical regimes: First, the relaxation time decreases linearly while the shell shrinks. Second, around the LCST at 32°C the relaxation time decreases rapidly until it (third) jumps around 38°C more than three orders of magnitude. This effect was determined as a function of concentration between 6 and 30 wt% and is not present in dilute systems. Furthermore, both the structural and the dynamical behavior were found to be reversible upon cooling down the system after heating.