Structure - mechanical property relations of polyelectrolyte multilayer and free-standing membranes

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Freestanding membranes with thicknesses on the nanoscale and well defined mechanical properties are valuable model systems for fundamental studies, but are also potentially interesting for applications like sensing or as micromechanical building blocks (switches, valves,...) - In particular polyelectrolyte multilayer membranes (PEMs) are promising in this respect because their thickness can be produced and precisely adjusted in the nanorange, and their compositon can be controlled on the molecular level. It is well known that PEMs can have strongly differing mechanical properties, depending on their molecular scale structure (composition, intramolecular interactions). However a quantitative understanding of these structure property relations is missing so far. In the proposed project, we want to build up freestanding multilayers which are well defined in their structure, in particular in their (ionic and/or covalent) crosslinking densities and hydrophobic interactions between the layer forming molecules and study their mechanical properties. To do so, a comprehensive approach will be made, combining the synthesis of novel, tailored polyelectrolytes for layer buildup with the development of mechanical characterization techniques for the new freestanding polyelectrolyte membranes. This will not only shed light on the static mechanical properties of PEMs, but also provide the basis for understanding and tailoring the responsiveness of these materials towards environmental changes such as of pH and of salt concentration.