Polyolefins represent one of the major products of the plastic industry, that satisfy 55 % of the worldwide plastic demand. However, due to their chemical composition, they suffer of scarce surface properties, such as dyeability, compatibility with other materials, printability and adhesion. In this regard, the introduction of polar functional groups into the polyolefin skeleton would overcome this problem. Up to now this target is industrially achieved by radical polymerization reactions, that require harsh conditions of temperature and pressure and do not allow the control on the microstructure of the produced functionalized polyolefin. The direct, homogeneously catalyzed copolymerization reaction of ethylene with polar vinyl monomers would overcome all of these limits, allowing to use milder reaction conditions but, most importantly, to have a precise control on the copolymer microstructure. Much efforts have been done in this direction, and in the last two decades a wide number of systems based on palladium catalysts with a great variety of ligands has been reported. However, the catalytic performances of these systems, in terms of activity/productivity values, incorporation of the polar monomers, molecular weight and molecular weight distribution and copolymer microstructure, do not satisfy the requirements for a potential industrial application, thus better performing catalysts are needed.
This PhD thesis aims to develop new homogeneous catalysts for the target reaction based on palladium(II) complexes with bidentate nitrogen-donor ligands (N-N). The strategy of this research project is based on expanding the library of N-N donor ligands reported in literature, and to study the influence of the ligand design on the catalytic outcome. In each Chapter the synthesis and characterization of different N-N ligands will be reported, along with the synthesis and characterization of the relevant Pd(II) complexes, and the study of their catalytic behaviour including the characterization of the catalytic products.
