Synthesis Of PES-based Polyether-ester And Its Copolymerization With Polylactic Acid

Polyethylene succinate（PES）,as an aliphatic polymer synthesized from biological monomers,is expected to replace the traditional petroleum-based polymer materials because of its good thermodynamic properties and excellent biocompatibility.However,the single performance of PES limits its application range.In order to expand the application field of PES,researchers usually modify PES by copolymerization and blending.In the copolymerization of PES,highly toxic solvents or chain extenders are often used.At the same time,the low molecular weight of the synthesized PES copolymer also greatly limits the subsequent processing performance.In this paper,PES-based polyether-ester materials with different structures and properties were synthesized through low toxicity catalyst system,and the reaction mechanism and the influence of structure composition on PES-based polyether-ester materials were studied.In this work,PES-based polyether-ester with high molecular weight was synthesized by melt polycondensation in one pot with succinic acid and ethylene glycol as raw materials,and the reaction mechanism of the catalyst was analyzed.This method effectively avoids highly toxic reaction raw materials and harsh reaction conditions.Through the selection of experimental conditions,a series of PES-based polyether-esters with different structure were synthesized by using Titanium（IV）isopropoxide（TPT）and Methane sulfonic acid（MSA）as binary catalyst system.In the process of reaction,sulfonic acid catalysts catalyze esterification and etherification at the same time,so that PES-based polyether-ester materials can be synthesized without polyether diol.At the same time,high molecular weight PES-based polyether-ester materials with specific structural composition can be synthesized by adjusting the monomer feeding ratio.With the increase of ethylene glycol dosage,the content of diethylene glycol succinate（DEGS）and oligopoly ethylene glycol（OEGS）structural units in PES-based polyether-ester increased.The addition of DEGS and OEGS enhances the flexibility of the material and reduces the glass transition temperature of the material.The crystal structure of PES-based polyether-ester was not affected,and the melting point（T_m）and melting enthalpy（?H_m）decreased with the increase of DEGS and OEGS structural units.When the content of OEGS reaches 34%,PES-based polyether-ester materials do not crystallize at all.When the feed ratio of succinic acid to ethylene glycol is 1:1.05,the number average molecular weight of PES₈₉-PDES₁₁ can reach 87000 g/mol,and has higher elastic modulus（248 MPa）and tensile strength（25.5 MPa）than PES.As a biodegradable material,polylactic acid（PLA）is non-toxic and has excellent mechanical properties such as high strength and high modulus.However,polylactic acid lacks toughness,which greatly limits its application as general plastics.The copolymerization modification of polylactic acid often uses highly toxic reaction conditions,and the low molecular weight of the synthesized copolymerized material affects the subsequent processing of the material.In this work,PES-based polyether-ester was copolymerized with polylactic acid by melt polycondensation,and copolymer PEDES-PLA with different lactic acid component content was successfully synthesized by one pot method.The number average molecular weight of copolymers is higher than 45000 g/mol,and the mechanical properties of some copolymers（tensile strength of 28.1 MPa,elongation at break of more than 650%）are much higher than the national standard of plastic bags.When the content of lactic acid is 30-70%,the weight loss rate of copolymer lipase degradation can reach more than 90%in 35 days.The glass transition temperature of the copolymer increases with the increase of polylactic acid components.The copolymerization of polylactic acid with PES-PDES greatly improves the thermal stability of polylactic acid.A series of polymers with adjustable structure and composition were synthesized by one pot method,which is expected to be used in various fields.