Nanometric and sub-nanometric structural properties of complex functional materials by means of solid-state NMR techniques

This thesis is about the application of SSNMR techniques to the study of different kind of functional materials with the aim of shedding light on the correlations between the structural and dynamic properties on a nanometric and sub-nanometric scale and the functional behaviour. This thesis is articulated in seven chapters. Chapter 1 introduces the SSNMR framework, presenting the theoretical background necessary to the comprehension of the SSNMR studies described in Chapters 3-7. Chapter 2 contains an introduction to functional materials, particularly focusing on the correlations between “microscopic” properties and functional behaviour, and on the role of SSNMR in the study of these systems. Then, in the remaining Chapters, the most important SSNMR studies that I carried out during my PhD on different classes of functional materials are presented. Each chapter starts with a presentation of the materials investigated, along with the results obtained by other experimental techniques, if present. The presentation of the SSNMR results is supported by descriptions of the employed SSNMR techniques and methodologies, which were different for the different studies. Chapter 3 presents an example of the application of SSNMR to the study of a novel anion exchange membrane based on polymeric materials. The combination of 13C CP/MAS experiments with 1H T1 and T1ρ measurements allowed information on the phase and structural properties of both the polymeric matrix and the conductive functional groups to be obtained, so contributing a complete and detailed picture of the properties of the material to be achieved. In the study reported in Chapter 4, the phase and dynamic behaviour of polymeric luminescent indicators were investigated, with the final aim of identifying the processes, occurring at a molecular and/or supramolecular level, responsible for the luminescent response of these materials under heating. In this case, the analyses of on resonance 1H FIDs acquired at increasing temperatures was found to be a very powerful tool for investigating the phase transformations occurring in polymeric domains, providing both structural and dynamic information. In Chapter 5 a detailed characterization of the dynamic properties in polymeric photoactive materials for solar cells is presented. In particular, the simultaneous analysis of 1H and 13C T1 curves as functions of temperature through suitable theoretical models was used to achieve a detailed characterization of the motional processes occurring in the MHz regime. Chapters 6 and 7 deal with the application of advanced high-resolution SSNMR techniques to the measurements of 19F and 1H chemical shift anisotropies in crystalline materials containing both organic and inorganic components. In Chapter 6, a methodological approach for the measurement of 19F chemical shift anisotropy based on both the analysis of spinning sideband profiles and the use of two-dimensional recoupling experiments is presented, along with the results obtained on two reference samples. Finally, Chapter 7 contains the applications of the methods described in Chapter 6 to the structural chararacterization of different zirconium phosphonates.