Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 2: DRG-DPG SYMPOSIUM Rheology II

CPP 2.1: Hauptvortrag

Montag, 25. Februar 2008, 14:00–14:30, C 130

Shear induced structures in lamellar systems: from layers to onions to onions and layers — •Walter Richtering — Physikalische Chemie RWTH Aachen

The size growth of multilamellar vesicles (MLV, *Onions*) of a non-ionic surfactant system composed of 40wt% C10E3 in D2O was investigated by shear quench experiments, i.e. when the shear rate is reduced. The structural changes were monitored with the help of Rheo-Small Angle Neutron Scattering (SANS), Rheo-Small Angle Light Scattering (SALS) and optical microscopy. Two different pathways were observed. A continuous growth of vesicle size was found when the shear rate was reduced within the stability region of monodisperse MLV (Region III). However, a discontinuous pathway was observed for shear quenches from the monodisperse into the polydisperse MLV region (Region II). A shear quench into the high shear rate part of region II leads to a formation of lamellar domains which themselves follow the pathway of MLV formation in coexistence to the initial MLV structure. A shear quench into the low shear rate part region II leads to the formation of lamellar macro-domains, which display a tumbling behaviour and grow with time until the MLV formation process starts.