A series of biodegradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-butylene adipate-co- ethylene terephthalate-co-ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic...A series of biodegradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-butylene adipate-co- ethylene terephthalate-co-ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic acid (AA), 1,4-butanediol (BG) and ethylene glycol (EG) through direct esterification and polycondensation. The sequence structure and crystallinity of the copolyester were investigated by 1H NMR spectroscopy and the wide-angle X-ray diffractometry (WAXD). The analytical results showed that the PBATE copolyester was a random copolymer and the composition of PBATE copolyester was almost consistent with the feed molar ratios. The crystal structure of PBATE copolyester belonged to the triclinic crystalline system; The variation in melting point of the synthesized PBATE copolyester agreed well with the estimation obtained by the Flory equation and was applicable to the random copolymer.展开更多
Polyesters,such as polylactide(PLA),are a class of biodegra-dable and biocompatible polymers that have received increasing attention in biomedicine,agriculture,and commodity thermoplastics[1-2].However,the lack of pen...Polyesters,such as polylactide(PLA),are a class of biodegra-dable and biocompatible polymers that have received increasing attention in biomedicine,agriculture,and commodity thermoplastics[1-2].However,the lack of pendant functionality of conventional polyesters makes it difficult to modify and modulate the physicochemical properties in subsequent applications[3-4].Since 2006[5],the ring-opening polymerization(ROP)of O-carbox-yanhydrides(OCAs),which can be readily synthesized from amino acid or hydroxyl acid precursors,has been recognized as a promising route to functionalized polyesters[3-4].However,due to the increased methine C-H acidity,significant racemization of the stereogenic center and decreased stereoregularity have been identified for most OCAs,for instance,ManOCA[6](OCA from mandelic acid)and SerOCA[7](OCA from serine),when using typical 4-(dimethylamino)pyridine(DMAP)as catalyst.To minimize epimerization,some classical metal-based catalysts of coordination polymerization have been introduced to mediate ROP of OCAs,furnishing isotactic polyesters[8].展开更多
The composition and sequence distribution of monomeric units in polyester polyether multiblock copolymer were studied by pyrolysis? gas chromatography (PGC) and pyrolysis gas chromatography/mass spectrometry (PGC/M...The composition and sequence distribution of monomeric units in polyester polyether multiblock copolymer were studied by pyrolysis? gas chromatography (PGC) and pyrolysis gas chromatography/mass spectrometry (PGC/MS). PGC was applied to study the F t curve of the multiblock copolymer and PGC/MS was used to separate and identify the pyrolyzates. DTA experiment was used to study the decomposition temperature. The results show that the beginning point of elastomer’s decomposition was about 300?℃ and the decomposition temperature of most of the sample was 550?℃. Many pyrolyzates were produced because of the breaking of weak bonds in the sample. The possible microstructure was verified and the pyrolysis pathway of the copolymer was investigated.展开更多
文摘A series of biodegradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-butylene adipate-co- ethylene terephthalate-co-ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic acid (AA), 1,4-butanediol (BG) and ethylene glycol (EG) through direct esterification and polycondensation. The sequence structure and crystallinity of the copolyester were investigated by 1H NMR spectroscopy and the wide-angle X-ray diffractometry (WAXD). The analytical results showed that the PBATE copolyester was a random copolymer and the composition of PBATE copolyester was almost consistent with the feed molar ratios. The crystal structure of PBATE copolyester belonged to the triclinic crystalline system; The variation in melting point of the synthesized PBATE copolyester agreed well with the estimation obtained by the Flory equation and was applicable to the random copolymer.
文摘Polyesters,such as polylactide(PLA),are a class of biodegra-dable and biocompatible polymers that have received increasing attention in biomedicine,agriculture,and commodity thermoplastics[1-2].However,the lack of pendant functionality of conventional polyesters makes it difficult to modify and modulate the physicochemical properties in subsequent applications[3-4].Since 2006[5],the ring-opening polymerization(ROP)of O-carbox-yanhydrides(OCAs),which can be readily synthesized from amino acid or hydroxyl acid precursors,has been recognized as a promising route to functionalized polyesters[3-4].However,due to the increased methine C-H acidity,significant racemization of the stereogenic center and decreased stereoregularity have been identified for most OCAs,for instance,ManOCA[6](OCA from mandelic acid)and SerOCA[7](OCA from serine),when using typical 4-(dimethylamino)pyridine(DMAP)as catalyst.To minimize epimerization,some classical metal-based catalysts of coordination polymerization have been introduced to mediate ROP of OCAs,furnishing isotactic polyesters[8].
文摘The composition and sequence distribution of monomeric units in polyester polyether multiblock copolymer were studied by pyrolysis? gas chromatography (PGC) and pyrolysis gas chromatography/mass spectrometry (PGC/MS). PGC was applied to study the F t curve of the multiblock copolymer and PGC/MS was used to separate and identify the pyrolyzates. DTA experiment was used to study the decomposition temperature. The results show that the beginning point of elastomer’s decomposition was about 300?℃ and the decomposition temperature of most of the sample was 550?℃. Many pyrolyzates were produced because of the breaking of weak bonds in the sample. The possible microstructure was verified and the pyrolysis pathway of the copolymer was investigated.
