Application Of The Second-Coordination-Sphere Effect In Ring-Opening Polymerization And Olefin Polymerization

Polyester and polyolefin are two kinds of extremely widely used polymers.The improvement of their production process and the polymer properties are of great significance.In the last few decades,metal complexes catalyzed polymerization has enjoyed great successes both in industry and in academia.Since the discovery of Zieger and Natta catalysts,the design and modifications of various ligands have been the dominating scenario in this field.However,the incorporation of polar monomer is challenging due to the unfavorable interactions of the polar monomer with the activated metal center,leading to the deactivation of the catalysts.To develop new catalysts with high functional tolerance has become the focus of our work.In this dissertation,we designed two new sets of catalysts that have modified ligands.Through the introduction of ligand second-coordination-sphere,we were able to stabilize the active metal center in the polymerization to improve the activity and copolymer performance.1.A series of pyrrolylaldiminato ligands and the corresponding aluminum complexes were prepared and characterized.These metal complexes contain side arms bearing oxygen,sulfur moieties,which can influence their catalytic properties.In the presence of one equivalent of benzyl alcohol initiator,these complexes can initiate well-controlled ring opening polymerization of ?-caprolactone with high activities.Most interestingly,the well-controlled behavior was maintained in the absence of the benzyl alcohol initiator.2.A series of phosphine-sulfonate Pd and Ni catalysts baring oxygen substituents were prepared and characterized.The facile interaction of the pre-installed polyethylene glycol unit with the metal center or the polar monomers could modulate the ethylene polymerization and copolymerization processes.In ethylene polymerization,this strategy leads to enhanced activity,catalyst stability and polyethylene molecular weight.In ethylene copolymerization with polar monomers,improvements in all the copolymerization parameters could be realized.This effect is most dramatic for polar monomers with hydrogen bond donating ability.