Synthesis Of Schiff Base Aluminum Catalyst And Its Application In Ring Opening Polymerization Of Lactide And Caprolactone

As a polymer material,polylactide?PLA?has good degradability and excellent mechanical properties.There are a wide application prospect in the fields of biomedicine and food packaging.At present,polylactide with high molecular weight and good controllability is mainly prepared by ring-opening polymerization of lactide catalyzed by metal organic catalyst.But in practical application,a stable catalytic system with atomic economy and controllability is needed.At the same time,lactide homopolymer has some shortcomings in application.In order to overcome these shortcomings,the ring-opening copolymerization of lactide with another monomer makes the characteristics of each homopolymer reflected in the copolymer successfully.Therefore,it is of great significance to develop catalysts with high stability,atomic economy,controllability and good copolymerization performance.Two catalytic systems,bimetallic schiff base aluminum and monmetallic schiff base aluminum were designed and synthesized in this paper.In the first part,two bimetallic aluminum complexes syn-Al₂ and anti-Al₂ with different atomic distances were successfully designed,synthesized and characterized.Two bimetallic aluminum complexes syn-Al₂ and anti-Al₂ can efficiently catalyze rac-LA ring opening polymerization.However,when benzyl alcohol is in excess,only the syn-Al₂ that adjoining metal complex of two metallic aluminum atoms can exhibit immortal polymerization properties.This is illustrated by a variety of analytical methods.We have shown that anti-Al₂ has low stability through nuclear magnetic research.The syn-Al₂ catalyst was stable,consistent with the atomic economy and good controllability.In the second part,we successfully designed,synthesized four simple mono-metal aluminum complexes.These four complexes can effectively catalyze the homopolymerization of the two monomers,and the complex with large steric hindrance group Ph₂CH have better controllability than the other three complexes.Then we use the four kinds of single metal aluminum complexes synthesis the copolymer of rac-LA and?-CL.Complex 4 catalyzes the two monomers to produce a nearly perfect random copolymer.It has been proved by many methods that we can obtain random copolymers.And then the Ph₂CH group was introduced into other catalytic systems,and it was also successful.Hopefully this will lead to more systems.