Synthesis And Properties Of Aliphatic Polyester-based Multiblock Copolymers With Poly (Diethylene Glycol Terephthalate) Being Hard Segment

Biodegradable polyesters refer to polymers that can be completely or partially degraded into monomers,oligomers,CO₂,H₂O,and other substances harmless to nature under the action of enzymes,microorganisms,and/or water.Biodegradable polyesters not only have the advantages of traditional polyesters such as light weight and convenient,but also biodegradable,renewable,and pollution-free.Poly（butylene succinate）（PBS）and poly（ethylene succinate）（PES）are two typical biodegradable polyesters.PBS,as a kind of biodegradable polyester,has been studied a lot,but high crystallinity and poor toughness make PBS not suitable to meet a wider range of applications.In this work,1,6-hexamethylene diisocyanate（HDI）was used as a chain extender,and an amorphous poly（diethylene glycol terephthalate）（PDEGT）segment of different mass ratios was introduced into PBS to synthesize poly（butylene succinate）-b-poly（diethylene glycol terephthalate）multiblock copolymers（PBS-b-PDEGT）,and a series of tests were performed.PBS-b-PDEGT had a good thermal stability and may meet general processing requirements.It could be found that the introduction of PDEGT hardly reduced the melting point（T_m）of PBS-b-PDEGT.The crystallization mechanism and crystal structure of PBS didn’t change,but the crystallinity（X_c）decreased.The results of scanning electron microscopy demonstrated that PDEGT distributed in the PBS matrix in rod shape,and the system was partially compatible.All PBS-b-PDEGT samples showed good mechanical properties.As the proportion of PDEGT segment increased,the Young’s modulus（E）of PBS-b-PDEGT gradually decreased and the elongation at break（ε）increased significantly.Theεof PBS-b-PDEGT4 with40wt%of PDEGT was even as high as 746.3±29.1%,an increase of 358.6%compared to PBS,while the tensile strength（σ_b）was not reduced.PES has the similar chemical structure to that of PBS,which also has high crystallinity but its crystallization rate is slower than that of PBS.The poly（ethylene succinate）-b-poly（diethylene glycol terephthalate）multiblock copolymers（PES-b-PDEGT）were obtained by a block copolymerization of PDEGT and PES prepolymers in the same way as PBS-b-PDEGT.The thermal decomposition temperature at 5%mass loss of PES-b-PDEGT was higher than 300 ^oC,which could meet general processing requirements.Similarly,the scanning electron microscopy results showed that PES and PDEGT were partially miscible,and their phase morphology presented a typical sea-island structure.The spherulites of PES-b-PDEGT were looser than PES,and the nucleation density was reduced.After introducing the amorphous PDEGT segment,the E of PES-b-PDEGT increased,theσ_b first increased and then decreased,and theεincreased significantly.Theεof PES-b-PDEGT2 with 20wt%of PDEGT was even increased to 448.6±6.6%.In summary,PBS-b-PDEGT and PES-b-PDEGT with with high T_m and comparable mechanical properties were successfully prepared by a chain extension reaction in this dissertation,which will broaden the application range of PBS and PES in tough packaging and so on,and provide useful references for other related studies.