Study On The Preparation And Toughening Of PL-LA By Coordination Of Alkylaluminum Substituted By Biophenol With Molybdenum Catalyst

Environmental pollution caused by traditional plastic products is an important problem that affects human survival and development,and biodegradable materials can perfectly solve this problem.Polylactic acid(PLA)is expected to completely replace traditional plastics due to its renewable sources,degradable products,excellent mechanical strength and biocompatibility.However,the shortcomings of PLA hinder the popularization of PLA,such as the high strength and low toughness of polymer PLA,while the existing catalytic system of low molecular weight PLA can not both protect the environment and control the three-dimensional configuration of polymer products,so that it can not meet the needs of its medical market.Therefore,the synthesis of a more efficient catalytic system for the preparation of low molecular weight PLA and the effective toughening of PLA have become the focus of current researchIn this thesis,L-LA was synthesized by ring opening polymerization of L-LA catalyzed by different bio phenol instead of triisobutyl aluminum.The influence of polymerization conditions on polymerization activity and the influence of catalyst structure on product structure were studied systematically.The structure of the product was characterized by IR,NMR,DSC,XRD and POM.The crystallinity and morphology of the product were characterized by DSC,XRD and POM.The molecular weight and molecular weight distribution were characterized by GPC.The best polymerization conditions and the relationship between the structure of bio phenol and PLLA were obtained.It is found that the Al catalyst can be used to prepare pl-la in a simple process.Low molecular weight PLA with different crystallinity can be prepared by changing the structure and amount of bio phenol to change the structure of catalyst and the steric hindrance of substituents around the active center Al atom.And the molecular weight of pl-la just meets the conditions of pl-la as a drug release material,and PLA of this catalytic system is expected to be used in the field of drug release.In addition,human trace element Mo was introduced into the system as a cocatalyst to explore the effect of steric hindrance of substituents around the catalyst on the stereoregularity of PLLA.In order to achieve the strong toughness balance of PLA,we use 1,2-PB and L-LA as compatibilizers by in-situ grafting in the same polymerization system.Through the intermolecular force between the compatibilizer,1,2-PB rubber phase and PLA,the compatibilities were improved,and 1,2-PBwas uniformly dispersed in PLA matrix.At the same time,the microstructure of compatibilizer was characterized by IR and NMR,and the toughness and strength of PLA were characterized by stress-strain test.Secondly,we compared the PLA toughened by 1,2-PB,and explored the effect of intermolecular force and chemical bond combination on the toughening of PLA.The toughness and fracture strength of PLA were characterized by stress-strain test...