Dr Patrick Ilg

Structure and dynamics of complex fluids: macroscopic description from systematic coarse-graining

Soft matter systems respond sensitively to external perturbations, typically leading to anisotropic macroscopic properties.
On a microscopic level, soft matter systems are successfully described by interacting many-particle models obeying Newtonian dynamics for translational and rotational degrees of freedom. In order to capture the long-time, large-length scale behavior, coarse-grained descriptions of the orientational ordering and dynamics are urgently needed. Here, we discuss a general method based on projection operators and nonequilibrium thermodynamics in order to systematically and consistently connect microscopic and coarse-grained levels of description. We demonstrate the method for the examples of low-molecular polymer melts and nematic liquid crystals and show its benefits and limitations. Finally, we discuss possible applications of the method for complex interfaces.