Rheology of Complex Fluids (soft condensed matter)
	Once a inhomogeneous sample is considered one is experimentally and theoretically in dire straits. This particular situation is improved only slightly when one knows on the inhomogeneous nature of the sample. In the most cases a simple continuous sample is assumed and such "rheology on oversimplicated materials" will never provide a full understanding of material nor provides a satifactory interpretation of the found experimental results. The interpreation of measuring errors will add to such an uncomplete picture. On the other side, and this is it all about when rheology of complex materials is concerned, one is interested to study the internal interaction of whatever nature and size of the flowing material. The interaction of morphology and rheology can only be established when spatial and transient structural information on the non-equilibrium state is considered. Therefore, colloid science as well as physical chemistry is amoungst other of major importance in the research area of rheology of complex fluids.
	Projects
	Non-monotonic flow of fluids near phase transitions - Coupled shear induced structures and flow instabilities in complex soft condensed matter In non-monotonic flow, i.e. the non-linear flow of highly structured solutions one observes a separation of the sample into several differently sheared regimes. The material is able to aggregate temporarily in shear-induced structures that can cause flow instabilities or, vice versa, flow instabilities may force anisotropic aggregates into shear-induced structures. Caused by such anomalies in microscopic flow one observes in macroscopic rheology the typical shear-thinningor thickening behavior that is coupled with overshoots, unstable flow curves or oscillations in shear stress or shear rate. Non-monotonic flow is observed in technological important systems as liquid crystals, polymer melts and solution, and in surfactant and biopolymer solutions. During the last decade, a huge body of work was devoted to the observed shear induced structures since the combination of fluid mechanics, colloidal interactions and rheology attracted numerous researcher. Nevertheless, the complex interplay of the driving force, i.e. most experimentally observed phenomena in shear thinning and especially in shear thickening solution, are not well understood and is subject of the research project.
	Rheology and Rheo-optics of viscoelastic surfactant solutions
	Amphoteric surfactant solutions under flow