Synthesis And Properties Of Ethylene Brassylate Based Copolymers

In recent years in order to solve the“white pollution”problem,the EB which obtained from biology base is employed to synthesize long-chain polyesters by ringing-opening polymerization.It is considered as one of the most effective way to modify the maierials by copolymerization.Furthermore,the properties of copolymer are related to the crystallization property considerably.The recent researches has paied much attention on clarifying the crystallization behavior rather than investgating the relation between the crystallization behavior and other properties,such as thermal property,mechanical property and degradation property.Therefore,to clarify the relations are the basis of interpreting the change of properties,and that will provide a theoretical foundation of modifying the properties of copolymers.Ring opening copolymerization of ethylene brassylate?EB?and?-valerolactone??-VL?with various feeding ratios catalyzed by triphenyl bismuth was performed to prepare poly?ethylene brassylate-co-?-valerolactone?copolyesters.The molecular weight of copolymers range from 70 kg mol^-1 to 75 kg mol^-1,and the distribution of molecular weight range from 2.1 to 2.4.The reactivity ratios of EB and?-VL were firstly determined to be=0.64 and₍?1?=2.54,respectively.Then the copolymerization kinetics was traced and microstructure analysis showed that the chain structure of copolyesters were rearranged towards complete random as a consequence of transesterification reaction.The average sequence length of EB calculated by reactivity ratios is lower than experimental values whereas the average sequence length of VL is higher than experimental values.It indicates that the average sequence length calculated be reactivity ratio only suitable for the beginning of the reaction.On the other hand,the average sequence length of EB and VL calculated by feeding ratio fits the experimental values well,and that indicates that the distribution of both sequences is random.The resulting random copolymers were found to cocrystallize to exhibit isodimorphism phenomenon with a pseudo-eutectic point of melting temperatures and lattice spacings at 80 mol%?-VL units.Moreover,the variation of the lattice spacings confirmed that the comonomer units have better miscibility in the case of incorporation of shorter units into longer unit crystal than the opposite case.Finally,the continuously tunable mechanical properties of these copolyesters showed a similar pseudo-eutectic behavior at the same eutectic point of isodimorphism,which indicated that the correlation between isodimorphism and mechanical properties depending on composition is highly significant.A series of poly?ethylene brassylate-co-?-caprolactone?copolyesters with various composition ratios were synthesized by ring-opening copolymerization.The molecular weight of copolymers range from 70 kg mol^-1 to 75 kg mol^-1,and the distribution of molecular weight range from 2.1 to 2.4.The resulting random copolymers were found to cocrystallize to exhibit isodimorphism phenomenon with a pseudo-eutectic point of melting temperatures and lattice spacings at 75 mol%CL units.The crystal cell will be stretch in one dimension rather than expanding in both dimension with the incorporation of comonomer units.All elongations of copolyesters at break were significantly high?the highest elongations of copolyesters at break reached 2073%?,and the continuously tunable mechanical properties of these copolyesters showed a similar pseudo-eutectic behavior at the same eutectic point of isodimorphism.The intralamellar shear occurred at the low tensile rate whie both intralamellar shear and interlamellar shear occurred at high tensile rate.The copolymers exihibits excellent hydrolytic stability.