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978-3-8439-3085-7, Reihe Physik
Dynamics of polymer-water mixtures in confinement
167 Seiten, Dissertation Technische Universität Darmstadt (2016), Softcover, B5
This work studies the complex dynamics of polymer-water mixtures under two entirely different confinement conditions. The first confinement is an intrinsic molecular confinement, namely microcrystalline cellulose processed into paper. In this system, the single cellulose chains form inter-chain hydrogen bonds stabilising the crystal structure. Furthermore, these crystals produce cellulose fibrils, which again form larger fibres. This hierarchical structure leads to different geometrical confinements from the micrometre- down to the nanometre-length scale. Adding hydration water to this complex system has a severe impact on the polymeric dynamics. The second confinement studied in this work is provided by a droplet-phase microemulsion. The water core of these microemulsion droplets is loaded with the water-soluble polymer polyethylene oxide. So, the nanometre-sized droplets provide a so-called soft confinement to the polymer-water mixture.
It is possible to study the structure and dynamics of the confined polymer with neutron scattering due to an appropriate deuteration scheme. Independent from the droplet size, a significant increase of the polymer’s radius of gyration under confinement is found. This is in agreement with strongly attractive interactions between polymer and surfactant as proposed in literature. The increase in size is accompanied by a change in the polymer’s conformation. With regard to biological applications this is a crucial finding because for proteins and peptides conformation is directly related to biological functionality. On the investigated length scales, polymer dynamics are found to be purely diffusive in bulk as well as under confinement. In the latter situation, a complex interplay between droplet diffusion in oil and polymer diffusion in water is found.