Dresden 2017 – wissenschaftliches Programm
CPP 12.4: Vortrag
Montag, 20. März 2017, 16:00–16:15, ZEU 160
Structure and dynamics of colloidal short range repulsive interacting suspensions with weak attractive interactions. — Clara Weis and •Norbert Willenbacher — Karlsruhe Institute for Technology, Karlsruhe, Germany
The effect of weak attractive interactions on structure and dynamics of aqueous polymer dispersions is investigated using Multiple Particle Tracking (MPT) and classical rotational rheology. This allowed us to correlate microstructure, structural heterogeneities and local particle mobility in fluid, fluid/crystalline, glassy and gel like samples with the corresponding macroscopic flow behavior. For volume fractions φ < 0.5 good agreement between micro- and macro-viscosity was found. As weak attractive interactions were induced by adding non-adsorbing polymer, an enormous broadening of the fluid-crystalline co-existence regime was observed. MPT allowed for retrieving the phase composition, i.e. the fraction of the fluid and crystalline regions as well as the respective particle concentration, completely. In addition, the size of the crystals as well as their shear modulus could be determined. Further increasing attraction strength a gel state occurred and MPT disclosed a heterogeneous structure resembling a percolating network. At φ > φglass, the introduction of weak attractive interactions leads to a much broader fluid regime than predicted by MCT. At a given φ, stronger attractive interaction is required to form an attractive gel than for true hard sphere systems. MPT enables to study particle localization and structural heterogeneities on feasible, short time scales since a large number of dispersed particles are in the field of view.