Multinuclear Solid-State NMR Studies of Polymers and Immobilized Sonogashira Catalysts for Cross-Coupling Reactions



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The major directions of this thesis involve (1) the study of performance polymers with solid-state NMR techniques, (2) the synthesis, immobilization, and characterization of phosphine linkers on silica for immobilizing Sonogashira cross-coupling catalysts, and (3) the investigation of the coordinating strengths of phosphine linkers at Pd centers.

Solid-state NMR spectroscopy, a very versatile and comprehensive tool for the study of a wide range of materials, is at the center of this research. First, the treatment and characterization of high performance polymers for the oil and gas industry will be discussed. Performance polymers like polyaryletherketones (PAEK) are immensely important in energy applications due to their lower weight and superior corrosion resistance under demanding conditions. Blends of PAEK polymers, such as polyetheretherketones (PEEK) and polyetherketoneketones (PEKK), with polybenzimidazole (PBI) are of commercial interest due to their improved high-temperature stability and their superior wear characteristics.

However, regarding the PBI component, the origins of the properties that are disadvantageous in thermally or chemically aggressive environments are not well understood. The focal point of this research is the morphological and molecular changes of PEEK-PBI and PEKK-PBI blends after stirring them in liquid water and steam-treating them at high temperatures and pressures. The pure polymer components and the PAEK-PBI (50:50 wt%) blends are steam-treated at 150 ?C (ca. 300 ?F) and 315 ?C (ca. 600 ?F). Interactions and reactions of H2O with the functional groups of the polymers are studied using D2O in combination with IR, 2H MAS, and 1H wideline solid-state NMR. Three different processes taking place during high-temperature steam-treatment are identified.

In a parallel project the synthesis and characterization of chelating phosphine linkers, which are bound to silica via ethoxysilane groups will be described. These readily coordinate to the Pd and Cu complexes used for the Sonogashira reaction. This research brings forth new insights concerning the synthesis, immobilization and characterization of Pd(0)/Cu(I) Sonogashira catalyst systems as well as the optimization of the reaction conditions for the catalysis. Under the optimized conditions, and taking the coordinating strengths of the phosphine ligands, as determined by 31P HRMAS competition experiments, into account, catalysts that exhibit unprecedented activities and lifetimes are obtained.