Solid-state NMR studies of alkali fullerides and long-chain alkanes
The main focus of this thesis is the investigation of structure and motion of different materials by applying different solid-state NMR techniques. In the first section (1) some of the bases of NMR are described both in a Classical (1.1) and Quantum Mechanical (1.2) approach, while the next two sections deal with the experimental part of the work. In section 2 solid-state NMR studies of CsC60 are described and an unambiguous assignment of the 13C NMR spectrum of the polymer phase of CsC60, which is based solely on our experimental data, is presented. In contrast to previous work, the assignment does not rely on the knowledge of the electronic structure of this material and our results support a fully three-dimensional electronic structure as opposed to a quasi one-dimensional one. This is achieved using a two-dimensional 13C MAS NMR correlation experiment, which identifies nuclei coupled via a through-bond scalar interaction, the Refocused INADEQUATE. In section 3 solid-state NMR experiments performed on polyethylene and long-chain n-alkanes corresponding to the formula C246H494 are described. Particular attention is given to some specific issues such as chain folding and a detailed study of the saturation-recovery curves (T1) obtained is carried out for different materials. The model elaborated is able to simulate all the data recorded and the presence of an interphase between the crystalline and the amorphous parts of the samples is proposed. To help the understanding of the structure and the motion of long-chain n-alkanes in section 3 some deuterated samples such as C216H434-d24 and C12H25(CH2)192CHDC11D23+C162H326 ("the mixture") are also studied. Deuterium NMR is widely used and we fit all the experimental line shape of the different samples at different temperatures. Diverse models for the structure and motion of such materials are given, which take into account all the experimental results obtained.