Novel Organic Aluminum Catalysis For Ring-opening Polymerization Of Cyclic Ester In A Controlled Manner

Aliphatic polyesters,which combine both environmental friendly characteristics and sustainable property,have attracted much attention on academic and industrial interests.Among them,?-caprolactone(?-CL)and Lactide(LA)are the most widely studied.Coordination polymerization is an effective method to prepare aliphatic polyesters via insertion mechanism.However,the carbonyl group in the chain of aliphatic polyesters can also reacted with the central atom of the coordination polymerization catalyst,leading to transesterification side reaction.In addition,due to ring tension and space steric hindrance,the rate of homopolymerization and copolymeization were very different between cyclic ester.when copolymerization of LA/CL,the copolymer obvious tend to block polymer.Therefore,it is difficult to synthesize well-defined block copolymers and true random copolymers.According to the above problem,in this paper,we designed and synthesized novel organic ligands by changing the structure mode of organometallic catalysts,adjusted the density and steric resistance of metal central atoms.The purpose was to reduce the tendency of coordination reaction between the carbonyl group in the aliphatic polyester chain and the catalytic active center.The specific research contents summarized as follow:1.Synthesied and characterized a series novel of Aluminum complexes containing bulky aryl-?-ketiminato ligands.The electronic effect and steric hindrance effect on catalyst activity were studied.The ring opening polymerization of caprolactone and lactide can be efficiently and in controlled manner by Bn OH as the initiator.The bulky aryl-?-ketiminato Aluminum complexes can effectively inhibit transesterification side reactions.Prepared random copolymers with similar average lengths of the caproyl and lactidyl sequences by one-pot method.2.Synthesized and characterized a series novel of Aluminum complexes containing Salen ligand,Al complexes exhibiting excellent catalytic and good controllability performance toward the ROP of LA and CL under the condition of room temperature.They tested as the precursors for Ring opening polymerizations of?-pentadecalactone and Ambrette also exhibited excellent capability in controlling polymerization behavior.The obtained polymers with high molecular weight of polymer and narrow molecular weight distribution.3.Synthesis and characterized a series of the different ring of new Salen type ligand binuclear alumina catalyst.We further studied the selective polymerization and the activity of the ring-opening polymerization of Caprolactone by adjusting the length of amines,the rigidity,and steric hindrance effect.Salen type binuclear aluminum catalysts with different cyclic and bridging bonds exhibit high catalytic activity for the polymerization of caprolactone and lactide.Binuclear aluminum complexes on the polymerization of Lactide showed the cooperative effect.4.Utilized the mononuclear and binuclear aluminum complexes applied to stereoselective polymerization of rac-LA.The substituents of ligand on steric hindrance,electronic effect and coordination mode on selective polymerization were investigatied.The kinetic of ring opening polymerization of rac-LA studied by using ~iPr OH as initiator and 8a complex as catalyst.In addition,the conditions of polymerization optimized.