What is soft matter?

This relatively new term refers to a broad class of systems including rubber, plastic, paper, foams, soap solutions, liquid crystals, blood, biomembranes, biopolymers, and many others. Soft materials share a number of common features: energies are of the order of the thermal energy kT. Therefore, the systems respond strongly to weak external forces, and their properties are predominantly determined by entropic effects. In that sense, they resemble simple fluids. In contrast to simple fluids, however, soft materials display structure not only on the atomic scale, but also on mesoscopic scales (nano- or even micrometers).

Whereas these qualities fascinate statistical physicists, they also make it impossible to describe all aspects of a soft matter system within one single theoretical model. Thus there usually exist several models which operate on different length and time scales, and one of the great current challenges is to develop methods which link the scales with each other (multiscale modelling). Different models often have roots in different scientific disciplines: Soft matter science is a highly interdisciplinary field which brings together materials science, organic chemistry, physical chemistry, statistical physics, condensed matter physics, and biology.

In our group, we are particularly interested in phase transitions and surface and interface phenomena in soft matter, and in nonequilibrium phenomena. Among other, we study

  • Macromolecular systems , containing large molecules with many identical repeat units (polymers). Such molecules are usually very "floppy" and many of the properties of the materials are dictated by conformational entropy.

  • Amphiphilic systems : If molecules contain chemically incompatible units, i.e., units that tend to demix, this may lead to local phase separation, and to the formation of a variety of complex (locally or globally) ordered structures. Such processes often lie at the heart of self-organization in biological systems.

  • Colloidal systems: They can be viewed as model systems for solid matter and glasses, because times scales are slow and dynamics processes can often be studied through the microscope.

  • Anisotropic fluids and liquid crystals.

  • Biologically motivated problems related to biopolymers (e.g., DNA) or biomembranes