Application Of Homonuclear And Heteronuclear Metallic Phenoxides In ROP Of Cyclic Esters

Macromoleculer polyester, such as poly(lactide)(PLA) and poly(ε-capro-lactone)(PCL), and their copolymers, is a topic of current interest since they have numerous applications. Firstly, these polymers materials are derived from renewable feed stocks such as cornstalk or potatoes. Secondly, these polymers are biodegradable, biocompatible and nontoxic. Hence, polyesters can replace petroleum based products which are harmful to environment. At present, the major method to synthesize polyester is the ring opening polymerization (ROP) of cyclic ester monomer with the metal alkoxides as initiators. Therefore, the preparation of efficient catalytic systems is key to polyester industry. In recent years, homometal complexes as catalysts/initiators have been extensively studied. However, the studies of heterometallic complexes as catalysts are relatively seldom. Hence, on the basis of the synthesis of homometallic complexes this paper mainly focuses on the synthesis of heterometallic catalysts, and these complexes were applied to catalyze ROP of cyclic ester.This paper consists of three chapters:1. A brief review of ring about cyclic esters in recent years.2.Synthesis, characterization of homometallic complexe of Li supported by N,N,N′, M’-tetra((2-hydroxy-3,5-di-tert-butyl)benzyl)-1,2-ethanediamine tetraphenolate ligand and homometallic complexe of Al supported by N,N,N’, N’-tetra((2-hydroxy-3,5-dimethyl)benzyl)-I,2-ethanediamine tetraphenolate ligand and the application in ring-opening polymerization of cyclic esters:Experimental results show that homometallic lithium complex is an efficient catalyst for the ring-opening polymerization of lactide and homometallic aluminum complexe can catalyis the ring-opening polymerization of ε-caprolactone.3.Design, synthesis of a series of novel Al-Mg heterometallic complexes3、4and7supported by tetraphenolate ligand and the application ring-opening polymerization of lactide: Experimental results show that Al-Mg heterometallic complexe3is an efficient initiator for the ROP of lactide. Molecular weights of the polyesters are controllable, and the molecular weight distributions are narrow. Kinetic studies show that polymerization proceeds with first-order dependence on both monomer concentration and initiator concentration.