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

In this work, the possibilities of NMR relaxometry are exploited to study the molecular mobility and morphology of different multidomain polymer systems with liquid and solid state NMR and MRI.; First, the gelation mechanism of syndiotactic polymethylmethacrylate (sPMMA) in toluene is examined in detail by means of 13C liquid state NMR. By cooling down a mixture of sPMMA in toluene a coil-to-helix transition is observed in a first step followed by an association of the helices to form the physical junctions in the gel. The NMR relaxometry provided a quantification of the fractions with different molecular mobility by means of an extensive spin-spin relaxation time (T) investigation. It has been shown that NMR relaxometry in the liquid state can have an important contribution in the explanation of the gelation mechanisms of polymer systems.; Secondly, a comparative relaxometry study in the solid state is performed on poly(1,3-dioxalane)/polymethylmethacrylate (PDXL/PMMA) segmented networks and corresponding blends with different PDXL weight fractions (namely 20%, 40% and 60%). The study on the morphology is performed by means of the spin-lattice (T_1H) and the spin-lattice in the rotating frame (T_1ρH ) relaxation times. A homogeneous phase morphology on a scale of 20 nm is indicated by the same T_1H relaxation time for both constituents (PDXL and PMMA) in the segmented networks and in the blend with the lowest PDXL fraction. An increase of the PDXL fraction in the polymer blends leads to a heterogeneous phase morphology on the T_1H scale (domains larger than 20 nm).; Thirdly a MRI relaxometry study on polymers under load was performed. This allows to obtain localised information about cavitation and molecular chain mobility and cavitation induced by mechanical load. The pre-cracked specimen were mechanically loaded to yield stress in a stretching device that fits into the probehead. The four materials studied in this work contain a rigid matrix and a soft, elastomeric phase. Only the soft phase is visualised in the MRI images acquired with a spin-echo pulse-sequence since the transverse magnetisation of the rigid matrix decays to zero before the echo can be detected. (Abstract shortened by UMI.)...