Research

A rather large group of mostly organic materials is called soft condensed matter, for instance polymers, supramolecular structures of small organic molecules, liquid crystals, colloids, emulsions, biopolymers and biomembranes. Also included are structured and "interface dominated" materials such as microemulsions, block copolymers, foams, etc. All these materials are easily influenced by small external forces, they are "soft".

Large interatomar/intermolecular interaction energies (200-800 k_BT/Molecule)

due to electrostatic, metallic or covalent bonds

stable if subject to high pressures, high temperatures, high electric fields, ...

Weak Intermolecular Energies (< 25 k_BT/Molecule)

• van der Waals and electrostatic force
• hydration and hydrophobic Force
• molecular size and shape
• entropic effects
• cooperative effects

Intriguingly, a small change of one external parameter can induce a phase transition. For instance, a very prominent application is the liquid crystal display (LCD) used in watches or computer monitors. Still, many of the astonishing mechanical, electrical or optical properties found in nature are not yet realized in technical systems. Because they are not yet understood.

Even though Nature uses only very few chemical elements to build living matter (mainly H, C, N, O and P, with a little bit of Na, K, Cs, Cl, F, J, Sr, Ca, Mg, Mn, Fe, Zn) biomaterials are very complex. The cell of a bacterium consists of about 6000 different molecules. However, most biomolecules are just variations of a few basic molecular groups, mainly amino acids, nuclear bases, fatty acids, polyenes, phosphates and sugas. Biomaterials are self-organizing materials. The shape of the molecular groups, and the arrangement of hydrophobic, hydrophilic and charged groupes determine the supramolecular structures.

Monolayers at the Air Water Surface serve as model systems to probe the lateral interactions. In a Langmuir Trough many external parameters can be adjusted: temperature, area per molecule, content of salt, polymers or proteins in the water, organic molecules in the air side, etc. Additionally, the fluid interface is a large self-annealing surface, which is easily accessed by many techniques. We did and do research to address the following questions:

Nanocolloids have about the same radius as a swollen polymer coil. Like polyelectrolytes they are multiions. One may imagine two extrme cases, the polymer is either wrapped around the nanocolloid, or the nanocolloids are aligned on the polymer like beads on a string (bridging flocculation).