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Department für Chemie - Arbeitsgruppe Prof. Strey

PD Dr. T. Sottmann

Unfortunately left us Mr. Sottmann towards Stuttgart.

Publications

Find here the list of pubications.

CV

Thomas Sottmann studied physics at the University of Göttingen specializing in Physical Chemistry at the Max-Planck-Institute for Biophysical Chemistry, where he finished his Ph.D. in 1997. After one year as post-doc he moved to the Institute of Physical Chemistry at the University of Cologne. In 2006 he stayed as visiting professor at the Department of Chemical Engineering and Materials Science (CEMS), University of Minnesota.He holds 3 patents.

Self-Assembling Amphiphilic Systems

Surface active molecules are the key components of many physical, chemical, and biological systems. In the latter, phospholipids form the membranes of biological cells and thus comprise up to 80% of the dry mass of living organisms. Being more general, surface active molecules are known to self-assemble to form a rich variety of structures in solutions. The main driving force for this structure formation is the amphiphilicity of these molecules. In our group the thermodynamic, structural and interfacial properties of smart complex fluids are characterized with regard to their use in technical applications.

Microemulsions as Template Materials for Nanomaterial Synthesis

Complex fluids, as e.g. microemulsions are potential candidates for the synthesis of nanostructured polymeric materials. However, up to date the challenge is to copy the microemulsion structure to the desired structure of the polymer on a one-to-one scale. In most cases the changing monomer/polymer ratio lead to a phase separation during the polymerization process. In order to slow down the kinetics of the phase behavior we formulate highly viscous polymerizable microemulsions in which the hydrophilic sub-phase is replaced with concentrated sugar solutions (similar in spirit to the work of C. Co, J. Am. Chem. Soc. 126, 12746 (2004)). First experiments performed in close cooperation with the group of Prof- H.T. Davis (CEMS, University of Minnesota) indicate that the size of the obtained polymeric nanomaterial strongly correlates with the size of the underlying microemulsion.

Fig. 1: SEM-pictures of a polymerized highly viscous microemulsion. Left: lamellar structure; Right: bicontinuous structure

Properties of Supercritical Microemulsions

Mixtures of water and supercritical carbon dioxide (scCO2) have attracted much attention as environmentally friendly solvents. With certain surfactants single phase microemulsions containing water, carbon dioxide and surfactant can be formulated. Following the principle of supercritical microemulsion expansion (POSME, German Patent DE 102 60 815 B4) a low-cost nanoporous material should be achievable by expanding these near- and supercritical microemulsions. Home-made pressure cells allow us to study the phase behaviour and microstructure using DLS and SANS. Additionally, the membrane fluctuations of bicontinuous scCO2-water-microemulsions can be studied by neutron spin echo (NSE).

Fig. 2: SANS-curve of a supercritical CO2-microemulsion together with the home-made pressure cell.

Surfactant Bilayer Membranes doped with Stickerpolymers

The role of guest components like colloidal particles, proteins, DNA or synthetic polymers in bilayer membranes is of high relevance for biological processes. In order to clarify the impact of these molecules on the membrane properties we study the influence of stickerpolymers (synthesized by the group of Prof. D. Richter, NoE "SOFTCOMP" (NMP3-CT-2004-502235)) on surfactant bilayer membranes. First experiments show that replacing only small amounts of the surfactant by the polymer, both the as the isotropic sponge L3 and anisotropic lamellar Lα phase are considerably stabilized. Small angle neutron (SANS), small angle X-Ray (SAXS) and static light scattering in combination with systematic phase studies are used to elucidate the role of the stickerpolymers.

Fig. 3: Phase diagram of a binary water-surfactant system doped with stickerpolymers.

Soret Effect in Surfactant Systems and Microemulsions

Thermal diffusion (the Soret Effect) describes the migration of molecules in a temperature gradient and is one of the unsolved problems in physical chemistry. Many experiments show that the effect is strongly connected with the interface between the solute and the solvent. However in colloidal model systems the interfacial tension between the particle and the solvent is difficult to measure. On the other hand, in microemulsion systems the interfacial tension of a droplet can be controlled by changing the curvature of the amphiphilic film. In a DFG-project (SO 913, Wi 1684) with the group of S. Wiegand (FZ-Jülich) we just started to study the influence of the interfacial tension on the Soret coefficient of oil- in-water microemulsions.

Fig. 4: Thermal diffusion of dye-free and dye-infected micelles.