Synthesis, Characterization Of Aluminum And Zinc Complexes Supported By Phenoxide Ligands And Application In ROP Of Cyclic

Synthetic polymers have become an indispensable part of the daily-life of human beings, in particular the biodegradable class of aliphatic polymers such as PCL, PLA and their copolymers have been widely used in our daily life and the field of medicine like food packing, a delivery medium for controlled release of drugs, scaffolds for tissue engineering and so on due to their advantageous biocompatible, biodegradable and permeability properties. The major and effective way to synthesize the polyesters is the ring-opening polymerization(ROP) of cyclic esters catalyzed or initiated by metal complexes, producing polymers with well controlled molecular weight and low polydispersity (PDI). The development of well-defined metal complexes with high catalytic activity and excellent stereoselectivity has been attracting an increasing attention. In this paper, we mainly report the synthesis, characterization of aluminum complexes supported by bisphenol ligands and a zinc complex bearing monophenol ligands, and their catalysis in the ROP of ε-CL and L-lactide. This paper is composed of three chapters:In the first chapter, we briefly introduce the latest development of the ROP of cycle esters catalyzed by metal complexes and the application of polymers.In the second chapter, two aluminum complexes ([(TBBP)Al(CH3)(THF)](1) and [(TBBP)Al(μ-OiPr)]2(2)) supported by bulky bisphenol TBBPH2ligand have been synthesized and fully characterized on the basis of elemental analyses, NMR spectra, X-ray single crystal diffraction and so on. The alkoxy aluminum complex2was used as an catalyst for ROP of ε-CL and L-lactide, the experimental results exhibit that it can efficiently initiate the ROP of ε-CL in a living fashion under the optimized conditions, yielding polymers with favorable molecular weight and narrow polydispersity indexes, while the isopropoxide aluminum complex show slight catalytic activity towards ROP of L-lactide. The aluminum complex1reacts with a equiv of linear trisphenol in THF to yield a dimer of triphenol aluminum complex [Al(OArCH2ArOCH2ArO)]2(3) instead of a heterodimer of aluminum complex with one trisphenolate and one bisphenolate. We presume that may be resulting from the extreme unstability of the heterodimer of aluminum complex.In the third chapter, we mainly describe the synthesis, characterization of a novel netual zinc complex bearing sterically bulky benzotriazole phenoxide ligands and its catalysis in the ROP of ε-CL and L-lactide. In the presence of BnOH, the netual zinc complex presents moderate catalytic activity in the ROP of ε-CL and L-LA, producing plyesters with small polydispersity indexes.