Summary

This cross-sectional Q-project will investigate static and dynamical properties of different polymer networks using X-ray photon correlation spectroscopy (XPCS). Combined with other techniques such as Neutron spin echo or dynamic light scattering this will provide us comprehensive information on the defect-induced network dynamics over many time- and length scales. We will be able fill the gap of knowledge, as e.g., studying dynamics of metallo-supramolecular building blocks within a polymer network on the timescale of microseconds (B01). This is, project B01 investigates a model-network platform built by non-covalent linking of star-shaped four-arm polymeric building blocks. Using XPCS we will investigate the diffusion of modified cross-linkers in various environment at timescales that have not been accessible so-far. For the case of pure water, we previously identified by using XPCS a three-step relaxation process on femtosecond timescale and molecular length scale. Similar processes where identified in literature for specific building blocks within supramolecular polymer networks (e.g. protein hydrogels) on much larger length and timescales.

In the CRC we will use two different model systems in order to investigate their diffusion mechanism, namely the aforementioned supramolecular polymer networks (B01) and proteins in aqueous solution (B04). Here we will study both, the dynamic of proteins in solution, as well as the influence of defects (bound water in modified protein cavities) (B04) to the structure of the surrounding hydration water network. As an experimental cross-link project, we will further support all projects within the CRC framework in terms of X-ray scattering techniques. This is, we intend to use both our in-house facilities at MPI-P (Powder diffraction and small angle X-ray scattering) as well as large scale facilities such as storage rings and X-ray free electron lasers (XFEL). Small angle X-ray scattering (SAXS) can provide us information about spatial inhomogeneities in polymer-network gels. Further, time resolved Scattering will, e.g., be able to provide information about the self-assembly of amphipiles (1) (C01) and its size and shape. The here proposed experiments take advantage of recent developments, such as a new storage ring technology that allowed the fourth-generation of high-energy synchrotrons to emerge.

(1) Narayanan, T.; Gummel, J.; Gradzielski, M. In Advances in Planar Lipid Bilayers and Liposomes; Iglič, A., Kulkarni, C. V., Eds.; Academic Press, 2014; Vol. 20.