Solid state NMR for advanced materials characterization
An important objective of material science is to establish relationships between the microscopic distributed heterogeneities and the macroscopic properties of materials. This information is essential in order to design materials with improved properties. Spin-diffusion NMR represents an established method to investigate domain sizes and morphology of heterogeneous polymers. General analytical solutions were for the first time derived for an one-dimensional process in a model morphology system represented by three different domains with arbitrary sizes, diffusivities, and proton densities. Further on, an NMR approach to clarify the complex morphology of semicrystalline polymer systems was introduced. This approach uses a combination of dipolar filters that select the mobile and the rigid domains of a heterogeneous sample in combination with one-dimensional and multi-dimensional analytical solutions of the spin-diffusion equations adapted to a specific morphology. The above approach was successfully applied to clarify the morphology of Nylon-6 fibres. The particular set up of the spin-diffusion experiment using a MAPE dipolar filter reveals only the spatial distribution of the mobile amorphous domains and the aggregates of fibrils as a whole. An estimation of domain sizes of crystalline and less-mobile amorphous domains along the fibrils as well as the diameter of the fibrils and the inter-fibril distance could be achieved in a spin-diffusion experiment employing a double-quantum filter. The changes detected in the domain sizes were correlated with the processing conditions. Further on, 1H spin-diffusion measurements were used to estimate the domains sizes of the rigid amorphous, the interface, and the mobile amorphous regions of a series of (PEO-b-PHEMA) diblock copolymers with different molecular weights. Another interesting topic covered was related to biodegradable polymers having shape memory properties. Networks of [(L-lactide)-ran-glycolide]dimethacrylate with potential medical applications were characterized in terms of structure, mobility, shape memory properties, and degradation behavior in vitro. Further on, the molecular dynamic heterogeneities of thin lecithin films confined to submicron cylindrical pores were investigated using proton multiple-quantum and magnetization-exchange experiments. The surface induced orientation of the molecular chains which leads to the chain dynamics faster than in bulk. The effect of the surface coverage, the pore size, and the temperature on the heterogeneity of the chain dynamics was discussed. Additionally, a study of the interaction between the collagen and its water of hydration was done with the help of magnetization transfer experiments. The steps involved in this process as well as the functional groups contributing to it were identified and characterized.
info:eu-repo/classification/ddc/530, Polymere, Festkörper-NMR-Spektroskopie, Spindiffusion, Physik, NMR, spin-diffusion, polymer, fibres
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