Synthesis Of Poly(ether-ester)s From The Copolymerization Of Epoxides And Lactones

The aliphatic polyesters are important synthetic polymer materials.They have good compatibility,biodegradability and physical and mechanical properties and are considered as an ideal substitute for petroleum-based polymer materials.Polycaprolactone(PCL)is one of the most common and widely used polyesters.However,some drawbacks of the material such as their single structure nature,brittle and poor hydrophilicity limit its further development.Among them,the copolymerization of?-caprolactone(CL)and epoxides maintain the degradability of polyesters,and at the same time,the introduction of polyether segments effectively improve the properties of materials,such as toughness and hydrophilicity.However,the obtained copolymers ether ester have low alternating degree,poor molecular weight controllability,and lack of in-depth research on their mechanical properties.Therefore,it is of great significance to develop high efficient catalysts to realize the accurate synthesis of polyether-polyester copolymers and to study their properties.In this paper,a biphenyl-linked heteronuclear bimetallic catalyst was designed and synthesized for the copolymerization system based on epoxides and?-caprolactone to synthesize polyether-polyester copolymers with excellent properties.(1)A class of heteronuclear bimetallic aluminum-chromium complexes based on biphenyl or binaphthyl as the bridging group was designed and synthesized.The binuclear ligand was firstly reacted with Al Et₂Cl and isolated by column chromatography to give a purified single metal complex.Then,the obtained complex was further reacted with Cr Cl₂ to provide the dinuclear bimetallic complex.The structure of the catalyst was proved by analysis methods such as proton nuclear magnetic resonance spectrum,carbon spectrum,correlation spectrum and high-resolution mass spectrometry.(2)The above heteronuclear bimetallic complexes were used to catalyze the copolymerization reaction of CL and epoxides to synthesize the corresponding polyether-polyester copolymer.The results showed that the heteronuclear bimetallic catalyst based on biphenyl exhibited the excellent activity in catalyzing the copolymerization of CL and propylene oxide(PO),and the synthesized polymer showed a polyether-polyester gradient structure.The effects of the reaction temperature,the ratio of catalyst to cocatalyst,and the ratio of monomer to catalyst on the polymerization reaction were investigated.The research results showed that increasing the temperature or the PO/CL ratio can increase the ether-ester alternation rate in the polymer,the addition of a co-catalyst can change the copolymerization process and the ratio of the catalyst to the co-catalyst can affect the rate of the polymerization reaction and the polymer structure.The dynamic thermomechanical analysis study indicated the obtained copolymers possess enhanced flexibility,compared with the block copolymers or blend of PPO and PCL homopolymers with the same ratio.In addition,the catalyst also showed high catalytic activity in the copolymerization of CL and other epoxides such as 1,2-butylene oxide(BO),1,2-epoxyhexane(HO),and the resulting polymer also has high ether-ester alternation rate and good mechanical properties.This newly strategy provided a new research idea for the modification of PCL and the synthesis of high-performance polymer materials.(3)The copolymerization of CL/PO/Glutaric anhydride(GA)was realized by using biphenyl heteronuclear bimetallic catalyst.Studies showed that the reaction involves two polymerization processes:one is the alternating copolymerization of PO and GA,the other is the copolymerization of PO and CL.By investidating the effects of the ratio of monomer to catalyst on the polymerization reaction,it was found that increasing the content of GA can increase the alternating ratio of ether and ester in the polymer.The thermodynamic performance test showd that compared with PCL homopolymer,the thermal performance of obtained copolymers were enhanced,and with the increase of the molar amount of GA,the glass transition temperature was increased significantly,implying the thermal performance of the copolymer can be controlled by changing the alternating ratio of ether and ester in the copolymer.