The asymmetric alternating copolymerization of meso-epoxide and cyclic anhydrides provides an efficient access to enantiopure polyesters.Contrary to the extensive investigation of the stereochemistry resulting from ep...The asymmetric alternating copolymerization of meso-epoxide and cyclic anhydrides provides an efficient access to enantiopure polyesters.Contrary to the extensive investigation of the stereochemistry resulting from epoxide building block,the chirality from anhydride and the configurational match with epoxide remain elusive.Herein,we discover that the bimetallic chromium catalysts have led to an obvious enhancement in terms of reactivity and enantioselectivity for the asymmetric copolymerization of meso-epoxide with various non-symmetric chiral anhydrides.Up to 97%ee was obtained during the asymmetric copolymerization of cyclohexene oxide(CHO)with(R)-methylsuccinic anhydride(R-MSA),and three-or four-carbon chiral centers were simultaneously installed in the aliphatic polyester backbone.In particular,the different combinations of stereochemistry in epoxide and anhydride building blocks considerably affect the thermal properties and crystalline behaviors of the resulting polyesters.This study uncovers an interesting method for regulating polymer crystallinity via matching the chirality of different monomers.展开更多
Aliphatic polyesters were synthesized via the ring opening polymerization of the corresponding lactones initiated with dibutylmagnesium both in bulk and in solution. The resulting polymers were characterized by 1H, 13...Aliphatic polyesters were synthesized via the ring opening polymerization of the corresponding lactones initiated with dibutylmagnesium both in bulk and in solution. The resulting polymers were characterized by 1H, 13C NMR, GPC and XRD. The results indicated that dibutylmagnesium is an effective initiator for the ring opening polymerization of lactones.展开更多
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
Eggshell powder is a powdered product that is made from discarded eggshells. It is rich in inorganic salts and a small number of organic substances. Aliphatic polyester is one of the most promising polymer materials a...Eggshell powder is a powdered product that is made from discarded eggshells. It is rich in inorganic salts and a small number of organic substances. Aliphatic polyester is one of the most promising polymer materials at present. Aliphatic polyester has not only a wide range of sources, but also excellent biodegradability and biocompatibility. Three kinds of aliphatic polyester composites were mixed with PCL, PBS, PHA, PLA and Ag powder as raw materials through solution reinforcement by eggshell powder. The thermal properties and structures of the three materials were analyzed and characterized by differential scanning calorimetry and scanning electron microscopy. DSC and SEM were used to analyze and characterize the thermal properties and structures of the three composites. The experimental results show that the GTT(glass-transition temperature) are 91.9°C, 89.3°C, and 87.2°C, the melting points are all greater than 92°C, and the enthalpy changes are respectively -37.8J/g, -23.9J/g, -22.2 J/g,. Among them, the composite material of PCL, PBS and eggshell powder, and Ag powder has excellent performance, showing good thermal performance and thermal stability. Moreover, the production and utilization of eggshell powder, turning waste into wealth, has important economic value for the sustainable development of circular ecology.展开更多
Biobased urea nowadays attracts increasing attention as a biomass resource with giant potential,which benefits from the development of biobased ammonia and ecological sanitation system.Urea is an ideal feedstock for c...Biobased urea nowadays attracts increasing attention as a biomass resource with giant potential,which benefits from the development of biobased ammonia and ecological sanitation system.Urea is an ideal feedstock for chemical industry and developing new urea-based polymer materials can take advantage of the urea resource.In this work,a class of renewable linear polyesters,namely polyisocyanuratoesters(PICEs)were synthesized from a urea-based monomer bis(2-carbomethoxyethyl)isocyanurate and biobased aliphatic diols.Compared with conventional aliphatic polyesters,PICEs containing isocyanurate rings in the polymer chain backbone exhibit outstanding flame retardancy that both PICE-4(the number‘4’refers to the number of methylene in diols,e.g.4 for butylene and 6 for hexylene)and PICE-6 have high limiting oxygen index values over 30%.In the UL 94 tests,PICE-6 reaches V-1 rating;while V-2 is found for PICE-10.All PICEs exhibit similar pyrolysis behavior that the temperatures of 5%weight loss are around 320°C.PICEs are found to have glass transition among 20°C-45°C.No crystallization behavior is observed without annealing except for PICE-10,which can crystallize even at room temperature.展开更多
Aliphatic biodegradable polyesters have been the most widely used synthetic polymers for developing biodegradable devices as alternatives for the currently used permanent medical devices.The performances during biodeg...Aliphatic biodegradable polyesters have been the most widely used synthetic polymers for developing biodegradable devices as alternatives for the currently used permanent medical devices.The performances during biodegradation process play crucial roles for final realization of their functions.Because physiological and biochemical environment in vivo significantly affects biodegradation process,large numbers of studies on effects of mechanical loads on the degradation of aliphatic biodegradable polyesters have been launched during last decades.In this review article,we discussed the mechanism of biodegradation and several different mechanical loads that have been reported to affect the biodegradation process.Other physiological and biochemical factors related to mechanical loads were also discussed.The mechanical load could change the conformational strain energy and morphology to weaken the stability of the polymer.Besides,the load and pattern could accelerate the loss of intrinsic mechanical properties of polymers.This indicated that investigations into effects of mechanical loads on the degradation should be indispensable.More combination condition of mechanical loads and multiple factors should be considered in order to keep the degradation rate controllable and evaluate the degradation process in vivo accurately.Only then can the degradable devise achieve the desired effects and further expand the special applications of aliphatic biodegradable polyesters.展开更多
A new process was designed to modify the hydroxy capped aliphatic hyperbranched polyester, derived from 2,2 bis(methylol) propionic acid and trimethylopropane in which the crude polyester reacted directly with maleic ...A new process was designed to modify the hydroxy capped aliphatic hyperbranched polyester, derived from 2,2 bis(methylol) propionic acid and trimethylopropane in which the crude polyester reacted directly with maleic anhydride in bulk to transfer the hydroxy end groups to 4 carboxy 2 butante end groups. The modified polyester was characterized by IR, 1H NMR, DSC and viscosity measurement. The results indicated that no side reaction took place during the modifying step and the conversion for the reaction was calculated to be 88.9% based on the \+1H NMR spectra. The T g value shifted from 320 3 K for the crude polymer to 288 4 K for the modified polymer. Moreover, the UV curing coating of the midified polyester showed high performances in hardness, adhensive and water resistance. [WT5HZ]展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.22071016 and 21920102006)。
文摘The asymmetric alternating copolymerization of meso-epoxide and cyclic anhydrides provides an efficient access to enantiopure polyesters.Contrary to the extensive investigation of the stereochemistry resulting from epoxide building block,the chirality from anhydride and the configurational match with epoxide remain elusive.Herein,we discover that the bimetallic chromium catalysts have led to an obvious enhancement in terms of reactivity and enantioselectivity for the asymmetric copolymerization of meso-epoxide with various non-symmetric chiral anhydrides.Up to 97%ee was obtained during the asymmetric copolymerization of cyclohexene oxide(CHO)with(R)-methylsuccinic anhydride(R-MSA),and three-or four-carbon chiral centers were simultaneously installed in the aliphatic polyester backbone.In particular,the different combinations of stereochemistry in epoxide and anhydride building blocks considerably affect the thermal properties and crystalline behaviors of the resulting polyesters.This study uncovers an interesting method for regulating polymer crystallinity via matching the chirality of different monomers.
文摘Aliphatic polyesters were synthesized via the ring opening polymerization of the corresponding lactones initiated with dibutylmagnesium both in bulk and in solution. The resulting polymers were characterized by 1H, 13C NMR, GPC and XRD. The results indicated that dibutylmagnesium is an effective initiator for the ring opening polymerization of lactones.
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Eggshell powder is a powdered product that is made from discarded eggshells. It is rich in inorganic salts and a small number of organic substances. Aliphatic polyester is one of the most promising polymer materials at present. Aliphatic polyester has not only a wide range of sources, but also excellent biodegradability and biocompatibility. Three kinds of aliphatic polyester composites were mixed with PCL, PBS, PHA, PLA and Ag powder as raw materials through solution reinforcement by eggshell powder. The thermal properties and structures of the three materials were analyzed and characterized by differential scanning calorimetry and scanning electron microscopy. DSC and SEM were used to analyze and characterize the thermal properties and structures of the three composites. The experimental results show that the GTT(glass-transition temperature) are 91.9°C, 89.3°C, and 87.2°C, the melting points are all greater than 92°C, and the enthalpy changes are respectively -37.8J/g, -23.9J/g, -22.2 J/g,. Among them, the composite material of PCL, PBS and eggshell powder, and Ag powder has excellent performance, showing good thermal performance and thermal stability. Moreover, the production and utilization of eggshell powder, turning waste into wealth, has important economic value for the sustainable development of circular ecology.
基金The authors are grateful for the financial supports of the National Science Foundation of China(21404040)the Fundamental Research Funds for the Central Universities(2015ZM053)the State Key Laboratory of Pulp and Paper Engineering(201538).
文摘Biobased urea nowadays attracts increasing attention as a biomass resource with giant potential,which benefits from the development of biobased ammonia and ecological sanitation system.Urea is an ideal feedstock for chemical industry and developing new urea-based polymer materials can take advantage of the urea resource.In this work,a class of renewable linear polyesters,namely polyisocyanuratoesters(PICEs)were synthesized from a urea-based monomer bis(2-carbomethoxyethyl)isocyanurate and biobased aliphatic diols.Compared with conventional aliphatic polyesters,PICEs containing isocyanurate rings in the polymer chain backbone exhibit outstanding flame retardancy that both PICE-4(the number‘4’refers to the number of methylene in diols,e.g.4 for butylene and 6 for hexylene)and PICE-6 have high limiting oxygen index values over 30%.In the UL 94 tests,PICE-6 reaches V-1 rating;while V-2 is found for PICE-10.All PICEs exhibit similar pyrolysis behavior that the temperatures of 5%weight loss are around 320°C.PICEs are found to have glass transition among 20°C-45°C.No crystallization behavior is observed without annealing except for PICE-10,which can crystallize even at room temperature.
基金This work was supported by the National Key Technology R&D Program(Nos.2014BAI11B02,2014BAI11B03,2012BAI18B01)National Natural Science Foundation of China(Nos.11120101001,11421202,31370959,11572029,31470915)+3 种基金National key research and development program in China(No.2016YFC1100704,2016YFC1102202,2016YFC1101100)Beijing Nova Programme Interdisciplinary Cooperation Project(No.xxjc201616)Key Laboratory of Advanced Materials of Ministry of Education of China(Tsinghua University),Fok Ying Tung Education Foundation(No.141039)International Joint Research Center of Aerospace Biotechnology and Medical Engineering,Ministry of Science and Technology of China,and the 111 Project(No.B13003).
文摘Aliphatic biodegradable polyesters have been the most widely used synthetic polymers for developing biodegradable devices as alternatives for the currently used permanent medical devices.The performances during biodegradation process play crucial roles for final realization of their functions.Because physiological and biochemical environment in vivo significantly affects biodegradation process,large numbers of studies on effects of mechanical loads on the degradation of aliphatic biodegradable polyesters have been launched during last decades.In this review article,we discussed the mechanism of biodegradation and several different mechanical loads that have been reported to affect the biodegradation process.Other physiological and biochemical factors related to mechanical loads were also discussed.The mechanical load could change the conformational strain energy and morphology to weaken the stability of the polymer.Besides,the load and pattern could accelerate the loss of intrinsic mechanical properties of polymers.This indicated that investigations into effects of mechanical loads on the degradation should be indispensable.More combination condition of mechanical loads and multiple factors should be considered in order to keep the degradation rate controllable and evaluate the degradation process in vivo accurately.Only then can the degradable devise achieve the desired effects and further expand the special applications of aliphatic biodegradable polyesters.
文摘A new process was designed to modify the hydroxy capped aliphatic hyperbranched polyester, derived from 2,2 bis(methylol) propionic acid and trimethylopropane in which the crude polyester reacted directly with maleic anhydride in bulk to transfer the hydroxy end groups to 4 carboxy 2 butante end groups. The modified polyester was characterized by IR, 1H NMR, DSC and viscosity measurement. The results indicated that no side reaction took place during the modifying step and the conversion for the reaction was calculated to be 88.9% based on the \+1H NMR spectra. The T g value shifted from 320 3 K for the crude polymer to 288 4 K for the modified polymer. Moreover, the UV curing coating of the midified polyester showed high performances in hardness, adhensive and water resistance. [WT5HZ]
