Looking at molecular multidomain behaviour of polymer systems through NMR-relaxometry

Abstract

A general introduction into the basic principles of NMR spectroscopy is represented in Chapter 1, followed by a description of relaxometry. In Chapter 2, NMR relaxometry is utilised in the liquid state to examine the gelation mechanism of syndiotactic poly(methyl methacrylate) (sPMMA). By means of a spin-spin relaxation time study, components with a different molecular mobility and their accompanying fractions reveals a better understanding of the two step gelation mechanism of sPMMA in toluene. The phase morphology of segmented polymer networks and the corresponding polymer blends is examined in detail by 13C NMR relaxometry in the solid state in Chapter 3. The segmented polymer networks are nano-structured amphiphilic networks based on poly(l,3-dioxalane) (PDXL) and poly(methyl methacrylate) (PMMA) with varying PDXL/PMMA ratio. Small domain sizes are observed in all networks while for the blends the phase morphology strongly depends on the PDXL weight fraction. Chapter 4 contains three main sections in which different toughened materials are studied under load by MRI relaxometry. The materials are measured under load in the magnet. The first section describes the material response of acrylonitrile-butadiene-styrene (ABS) upon mechanical stress. Discrete damage bands in the damage zone are visualised in detail. Localised analysis of the spin density (M0), the spin-lattice (Ti) and the spin-spin (T2) relaxation time in these damage bands, reveals spatial dependent information about the molecular chain dynamics and cavitation as well under load as after unloading,. In the second section, a block copolymer of poly(butadiene terephthalate) (PBT) and poly(tetramethylene oxide) (PTMO) is investigated under load. Localised analysis of the T2 decay time shows a spatial dependent change in the chain mobility induced by the applied stress. Two types of polyamide 6 (PA6) specimen are investigated in section 3 of Chapter 4. One type contains pure maleic anhydride grafted ethylene-propylene (EPM-g-MA), dispersed in the PA6 matrix while the other type contains PA6 occlusions in the dispersed rubbery phase. Both types are examined under load and show remarkable differences in the behaviour of the molecular chain dynamics.