Thermal diffusion in Complex Fluids

Thermodiffusion, also called thermal diffusion or the Ludwig-Soret effect, describes the coupling between a temperature gradient and a resulting mass flux in a multicomponent system. Although the effect was already discovered in the 19th century by Ludwig and Soret there is so far no complete understanding for liquids. One interesting observation is the fact, that in liquid mixtures whose components differ widely in molecular mass, such as polymer solutions and colloidal suspensions, it is typically the heavier component that migrates to the cold region. There are, however, exceptions. We plan systematic studies of synthetic polymers and colloids to find out under which conditions the heavier particles move to the hot or to the cold side. Optical techniques, like holographic grating techniques, light scattering and interferometric techniques will be the most important experimental methods. For experimentalists with an interest in non-equilibrium thermodynamics and statistical physics, there is a possibility to cooperate in the development of new theory. Fore more detailed information see PhD_Studentship.pdf

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Hard to Ultra Soft Colloids

The subject of your research will be the shear flow induced deformation of polymer brushes, grafted to the surface of colloidal particles and micelles, and it's relation to the non-linear rheological behavior and stability of these hairy colloidal systems. The shear induced brush deformation and it's effects on colloidal micro structural order at larger concentrations will be studied by means of neutron-, X-Ray and light scattering in combination with insitu-rheology. For some of these hairy colloids, shear banding is observed. This is a hydrodynamic instability that leads to inhomogeneous flow profiles. These profiles will be studied by means of microscopy and spatially resolved heterodyne dynamic light scattering. Experience in scattering methods and/or rheology is appreciated but not necessary. Fore more detailed information see HUSCadd_post_doc_position.pdf

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Shear-banding in Complex Fluids

In the vicinity of two-phase regions, a shear-induced hydrodynamic instability in systems containing mesoscopic entities (like colloidal particles) may occur. This leads to patterned stationary states, far away from equilibrium. Experiments on two kinds of systems are planned : fd-virus particles (as a model system for rigid colloidal rods), and very soft colloids (spheres with an extended polymer brush). Optical techniques, like light scattering, neutron scattering and time resolved rheology will be the most important experimental methods. For experimentalists with an interest in theory, there is a possibility to cooperate in the development of new theory.

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on the Structure and Dynamics of Interfaces and near Walls

Microstructural order and dynamics of interfaces between coexisting phases in various phase separated colloidal systems and near walls will be studied by means of optical techniques, like surface sensitive dynamic light scattering, reflectometry and ellipsometry. In addition, interaction potentials of single colloidal particles with a wall will be studied for various kinds of colloidal systems, including mixtures, of for example colloidal spheres and polymers and rod-like colloids, by means of Total Internal Reflection Miroscopy.

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