Synthesis Of Cyclic Phosphazene/Urea System And Asymmetric Schiff Base Aluminum Catalyst And Their Application In Ring-opening Polymerization Of Caprolactone

Polycaprolactides（PCL）and polylactide（PLA）have excellent biocompatibility and biodegradability,and can be widely used in the fields of biopharmaceuticals,food packaging,paper coating and so on.The synthesis methods of polyester are generally:polycondensation and ring-opening polymerization.Condensation polymerization has many disadvantages,such as,stringent polymerization conditions,side reactions,long polymerization time.The conditions of ring opening polymerization are mild,the side reactions are few and the molecular weight of the polymer is controllable.Catalysts play an important role in ring-opening polymerization of cyclic ester monomers.Metal complex catalysts have the advantages of stable structure,diverse ligands and high selectivity at high temperature.The structure of organic catalyst is simple,stable,and the production has free of metal residues.In this paper,two kinds of catalysts,CTPB/urea organic catalyst system and asymmetric schiff base aluminum complex,were synthesized and used in ring-opening polymerization of caprolactone,valerolactone and racemic lactide,respectively.The specific research content is as follows:In the first part of our work,CTPB/urea organic catalyst system was synthesized and used in ROP of caprolactone and valerolactone.It was found that the CTPB/urea catalytic system showed high activity and selectivity for the ROP of those two monomers in the presence of alcohol as initiator.It is found that the introduction of ureas would significantly increase the catalytic control during ROP without sacrificing the catalytic activity of CTPB.Moreover,the polymerizations catalyzed by the title catalytic system exhibit immortal characteristics and thus thousands equivalent of monomer could be converted to polymer efficiently with desired MWs and microstructures.Linear diblock copolymer and star copolymers with three identical diblock arms could be readily synthesized by segment feeding using different alcohols as initiators.In the second part,o-phenylenediamine and trans-cyclohexanediamine were used as the intermediate framework to react with 3,5-ditert-butylsalicylaldehyde and 2-diphenylphosphorylbenzaldehyde in two steps to produce ligands with different structures.The ligand was coordinated with trimethyl aluminum to synthesize to L1-AlMe₂[L1=3,5-^tBu-2-（OH）C₆H₂-CH₂-NH-C₆H₄-N=CH-C₆H₄-2-PPh₂]、L2-AlMe₂[L2=3,5-^tBu-2-（OH）C₆H₂-CH₂-NH-C₆H₁₀-N=CH-C₆H₄-2-PPh₂].The structures were characterized by ¹H NMR,¹³C NMR,³¹P NMR and single crystal X-ray diffraction.Then,they were used in the ring-opening polymerization of the cyclic ester monomer.