Synthesis,characterization Of Quinolinyl [N,O] Coordinated Lithium Complexes And Their Application In Ring-Opening Polymerization Of Cyclic Esters

Polyolefins are made from non-renewable raw materials such as petroleum,but materials made of polyolefins cause a series of environmental problems when they are processed.Therefore,in the past two decades,polyester materials have gradually replaced traditional polyolefin materials.Polyester materials have so great biodegradability,biocompatibility and excellent mechanical properties that they have been widely used in many fields such as agriculture,food and medicine.One of the important ways to synthesize polyester materials is the ring-opening polymerization of lactones,and the synthesis of catalysts with high catalytic activity,high selectivity and low toxicity is an important research topic.In this thesis,a series of quinolinyl N,O coordination lithium metal complexes were designed and synthesized,and their structures were described.These catalysts were applied to the ring-opening polymerization of cyclic esters.The activity of the catalysts was discussed in detail.Then we discussed the effect of catalyst structure and substituents on catalytic activity.The specific content of this thesis is as follows:Chapter 1:It mainly summarizes the development of polyester materials,the methods of synthesizing polyester materials in recent years,the mechanism of ring-opening polymerization of cyclic esters,and various catalyst systems used in the ring-opening polymerization of polyesters.The focus is on the different activities and selectivities of organolithium compounds for the ring-opening polymerization of ?-CL and LA.Chapter 2:Using 2-methylquinoline as raw material,quinolinyl ligands were synthesized through a series of synthetic steps,and then a series of quinolinyl lithium metal complexes were synthesized,and the obtained lithium metal complexes were characterized and catalyzed ?-CL's ring-opening polymerization reaction.Studies have shown that at 100°C,in the presence of the initiator benzyl alcohol,all lithium metal complexes have catalytic activity on ?-CL,and the catalytic activities of different substituents have obvious differences.Compared with literature reports,the PDI distribution of the polymer product obtained in this article is narrower,but the reaction conditions are more severe.Chapter 3:The catalysis of lithium complexes on the ring-opening polymerization of rac-LA was studied.The results showed that the lithium metal complexes had higher catalytic activity for rac-LA at 35?.In the presence of the initiator,benzyl alcohol,the reaction mechanism belongs to the coordination insertion mechanism.In addition,it can be judged from the H NMR spectrum and the flight mass spectrum that there is a transesterification reaction in the reaction,and the resulting polymer has a broad molecular weight distribution.