Study On Ring-opening Polymerization Of 1,4-dioxan-2-one And Its Block Polymer By Organic Catalysis

Since the last century,the development and application of polymer materials have received extensive attention.Among them,synthetic polymers are considered as an invaluable gift of modern science and technology for their good performance and low cost.It is widely used in packaging,agricultural food,consumables,medical equipment,building materials,industry,aerospace materials and other fields,and has become an indispensable part of our life.However,most of the synthetic materials are not biodegradable.If they are not recycled after use,they will produce solid waste that pollutes the environment.Biodegradable polymers are environmentally acceptable and have advantages in biomedical applications.Therefore,in recent years,the research of biodegradable polymers has aroused great interest.Poly(1,4-dioxan-2-one)(PPDO)is a biodegradable aliphatic polyester.Due to its excellent flexibility,biodegradability and compatibility,it has attracted wide attention as biomateria.In general,ppdo can be obtained by the ring opening polymerization(ROP)of1,4-dioxan-2-one(PDO)with catalyst.However,the ring opening polymerization of PDO is slower due to its higher ring tension and more stable structure compared with other cyclolactones.The polymerization reaction often takes a longer time and the monomer conversion is still low.So far,most of the catalytic systems used for ring opening polymerization of PDO are metal catalysts.These catalysts are often complex in structure,expensive in price,and have biological toxicity.The problem of catalyst residue limits the application of ppdo in biomaterials.Therefore,the screening or preparation of a green,high activity,monomer applicability of organic non-metallic catalyst has become the main focus of current research.Among them,small molecules containing n-type organic bases have attracted much attention due to their high catalytic activity for the ring opening of lactide and other lactones.However,little research has been done on the polymerization of PDO,a monomer which is difficult to open the ring.In this paper,the ring opening polymerization of PDO was studied by using 1,8-Diazabicyclo[5.4.0]undec-7-ene(DBU)and 1,5,7-triazabicyclo [4.4.0]decane-5-ene(TBD)as catalysts.The specific research content is mainly divided into the following three parts:First,using DBU or TBD as catalyst,the catalytic behavior of DBU or TBD in ring opening homopolymerization of PDO was studied in detail by changing the initiator,reaction temperature,solvent and the ratio of monomer to catalyst.The structure of the polymer was characterized by nuclear magnetic resonance(NMR)and mass spectrometry(MS),and the reaction kinetics was investigated by in-situ FTIR.The catalytic mechanism of ring opening polymerization was explored in detail.Second,in the presence of an organic catalyst,PDO and ?-caprolactone(CL)were used to prepare a series of Poly(caprolactone)-block-Poly(1,4-dioxan-2-one)(PPDO-PCL-PPDO)triblock polymers by block copolymerization.The structure of the copolymers was analyzed and characterized by means of NMR and gel permeation chromatography,and the thermodynamic properties,hydrophilicity and mechanical properties of the copolymers were further studied in detail by means of differential scanning calorimetry,thermogravimetric analyzer and universal testing machine.Third,in the presence of organic catalyst,a novel block copolymer Poly(pentadecalactone)-block-Poly(1,4-dioxan-2-one)(PPDL-PPDO)was prepared by block copolymerization of pentadecanolactone(PDL)and PDO.The structure of copolymer was analyzed and characterized by NMR and gel permeation chromatography,and the compatibilization of copolymer as compatibilizer in the system of Polylactide/low density polyethylene(PLA/LDPE)was further studied.