Structured soft materials, made from small organic molecules or macromolecules of synthetic and biological origin, display multiple and tunable attributes, based not only on a large variety of chemical building blocks, but also on their ability to self-assemble into highly organised structures and materials. The function of soft-matter materials is thus encoded in their form, both in the specific conformations of individual molecules and in structures resulting from complex ordering processes. In general, the underlying self-assembly processes are governed by interactions between the components as well as various constraints imposed by the molecular structure of the components. In soft matter, the resulting final form is often generated by multiple assembly steps, typically separated by low energy barriers. In many cases, therefore, the kinetics of structure formation plays an important role. As a consequence, the final degree of molecular order is limited but nevertheless specific and complexity is high. This is in contrast to “hard matter”, where in most cases a high degree of long-range order is found, so that structural complexity must be enforced by top-down processing. In many applications, the desired function of macromolecular materials is based on their special mechanical properties; in others, soft matter systems are suited to functions such as switchable optical properties (liquid crystals), electronic or optoelectronic properties (organic semiconductors), spatial segregation of components into compartments (membranes) or biochemical activity (proteins).
Current soft matter research activities in Halle comprise synthetic chemistry, physical chemistry, theoretical physics, polymer physics, biophysics, and materials science. Besides design and preparation of specific molecules a thorough understanding of the basic principles of chemistry, physics and engineering of soft matter is the aim of our research. Various classes of materials are studied within the Institutes of Chemistry and Physics. A number of research groups investigate lipids and (amphiphilic) polymers that interact with bilayer membranes. The synthesis and ordering of special complex liquid crystals as well as their interaction with lipid membranes are studied. Research on design, ordering and dynamics of macromolecules is a central research topic.
The SFB TR 102 Polymers under multiple constraints: restricted and controlled molecular order and mobility, established in July 2011, investigates the relationship between formation of molecular order and mobility on the segmental scale on the one hand, and, on the other hand, the topology and conformation of macromolecules on a mesoscopic scale. In polymers, both scales are linked by the constraints set by the connectivity of the chain, which transfers the effect of local interactions to a larger length scale and vice versa. The SFB is a joint initiative of the universities of Halle and Leipzig and focuses on three groups of phenomena: polymer crystallisation, amyloid formation, and molecular order and mobility in nano-phase separated systems, always with a special focus on the effect of internal or external constraints. The complexity of polymer crystallisation arises from a combination of several internal constraints: connectivity, crystal packing, and the topology of the crystallising melt. It requires a reduction of conformational entropy and competes kinetically with the slow dynamics of the chain, especially entanglement dynamics. A number of projects focus on fundamental questions of bulk crystallisation of polymers by combining the synthesis of well-defined model macromolecules, experimental investigations of the process of crystallisation and theoretical and numerical modelling of crystallisation. Amyloids comprise periodic, fibrous structures, assembled from protein solutions under the constraints set by the sequence of the protein and specific molecular interactions. Amyloid formation is different from simple crystallisation and is associated with specific interactions; however, in analogy to polymer crystallisation, amyloids form by nucleation and growth, whereby kinetics plays an important role. The resulting structural motifs are more or less independent of the detailed molecular architecture. Structural and dynamic aspects of amyloid formation as a polymer physics problem are investigated mainly by NMR and by computer simulation methods. In many heterogeneous polymers local demixing leads to the formation of nanophases. Order and molecular dynamics in these systems are strongly constrained by confinement and the connection to neighbouring phases. Examples are block copolymers, side chain polymers or spider silk as a biological material. The Integrated Research Training Group Polymers: Random coils and beyond of SFB TR 102 provides in-depth training in interdisciplinary Soft Matter Research to doctoral students.
The ordering of lipid molecules into bilayer membranes and their interaction with liquid crystals and polyphilic molecules are studied in the Research Unit FOR 1145. The goal here is to understand the interaction of synthetic polyphilic molecules with phospholipid bilayer membranes, where an additional element of complexity is generated by tripartite interactions between the membrane, the polyphilic molecule and a third, neither hydrophilic nor lipophilic interaction partner, e. g. fluorophilic systems. The resulting structured bilayer membranes act as templates for self-organisation, for binding and recognition. FOR 1145 consists of six projects, dedicated to the synthesis of polymers by living and controlled polymerisation methods and their ordering into mono- and bilayers, the synthesis and ordering of small, polyphilic molecules into liquid crystals, and the investigation of interactions between lipid membranes and polymer molecules or nanoparticles. The corresponding ordering processes and their associated dynamics in liquid crystals and membranes are investigated by specific physicochemical methods such as Infrared-Reflection-Absorption-Spectroscopy (IRRAS), X-ray and neutron-reflection including gracing incidence techniques or solid state NMR spectroscopy. An important contribution to lipid membrane research and the interaction with (synthetic) organic molecules is provided by the ZIK HALOmem, where the dynamics of lipid molecules and proteins within bilayer membranes is studied by FCS methods and fluorescence microscopy. The understanding of two-dimensional ordering and organisation processes in lipid membranes also contributes to the understanding of the biological function of membrane proteins, which are important recognition and signalling elements of living cells and tissues.
Last modified: March 19, 2013 15:04
(letzte Änderung: 19.03.2013, 15:04 Uhr)