A series of multiblock copolymers of PLLA\|PEG(PLE) with high molecular weight were synthesized by coupling PLLA\|PEG\|PLLA triblock copolymers with succinic anhydride in the presence of ( N,N\| dimethylamino) pyridin...A series of multiblock copolymers of PLLA\|PEG(PLE) with high molecular weight were synthesized by coupling PLLA\|PEG\|PLLA triblock copolymers with succinic anhydride in the presence of ( N,N\| dimethylamino) pyridine(DMAP) and dicyclohexylcarbodimide (DCC).The results of the viscometry measurement,GPC and 1H\|NMR,elucidated that multiblock PLE copolymers with high content of short PEG segments( M n=2000) had been successfully obtained.The crystallinity of the copolymers was investigated by X\|ray diffraction.Mechanical testing showed that multiblock copolymers had relatively high tensile strength and large elongation.In a word,the measurements showed that the multiblock PLE copolymers had high content of short PEG segments( M n=2000),high molecular weight( M w～100,000),excellent hydrophilicity and mechanical properties.The results of cells cultured on the multiblock PLE copolymer indicated that it might be suitable to be utilized as cell scaffold for tissue engineering.展开更多
High molecular weight up to 80×10 4 of poly(L lactide)(PLLA) was synthesized by bulk polymerization of L lactide using stannous octoate as initiator. The influence of polymerization time, temperature and initiato...High molecular weight up to 80×10 4 of poly(L lactide)(PLLA) was synthesized by bulk polymerization of L lactide using stannous octoate as initiator. The influence of polymerization time, temperature and initiator concentration on the molecular weight of PLLA was studied. An enhancement technique named fibrillated compression moulding has been developed for preparing high strength PLLA rods with bending strength of 20 260 MPa and shear strength of 170 190 MPa respectivity.展开更多
Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolym...Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolymers and electrospun ultrafine fibers were investigated and compared with those of PLLA and PA4 blends. PLLA and PA4 were found incompatible and formed individual crystalline regions, along with reciprocal inhibition in crystallization. Electrospun fibers were highly hydrophobic, even if hydrophilic PA4 was the rich component. The crystallinity of either PLLA or PA4 decreased after electrospinning and PLLA-rich as-spun fibers were almost amorphous. Immersion tests proved that fibers of block copolymers were relatively homogeneous with micro-phase separation between PLLA and PA4. The fibrous structures of copolymers were different from those of the fibers electrospun from blends, for which sheath-core structure induced by macro-phase separation between homopolymers of PLLA and PA4 was confirmed by TEM, EDS, and XPS.展开更多
In this study, the poly（L-lactide）/poly（D-lactide） （PLLA/PDLA） blends with different optical purities of PLLA and various molecular weights of PDLA are prepared by solution mixing, and the stereocomplex formatio...In this study, the poly（L-lactide）/poly（D-lactide） （PLLA/PDLA） blends with different optical purities of PLLA and various molecular weights of PDLA are prepared by solution mixing, and the stereocomplex formation and phase separation behaviors of these blends are investigated. Results reveal that optical purity and molecular weight do not vary the crystal structure of PLA stereocomplex （sc） and homochiral crystallites （hc）. As the optical purity increasing in the blends, the melting temperature of sc （Tsc） and the content of sc （AHsc） increased, while the melting temperature of hc （Thin） hardly changes, although the content ofhc （AHhm） decreased gradually. The Tsc and AHsc are also enhanced as the molecular weight of PDLA reduces, and the AHhm reduces rapidly even though the Thin does not vary apparently. With lower optical purities of PLLA and higher molecular weights of PDLA, three types of crystals form in the blends, i.e., PLA sc, PLLA hc and PDLA hc. As molecular weight decreases and optical purity enhances, the crystal phase decreases to two （sc and PDLA hc）, and one （sc） finally. This investigation indicates that the phase separation behavior between PLLA and PDLA in the PLLA/PDLA blends not only depends on molecular weights, but also relies on the optical purities of polymers.展开更多
文摘A series of multiblock copolymers of PLLA\|PEG(PLE) with high molecular weight were synthesized by coupling PLLA\|PEG\|PLLA triblock copolymers with succinic anhydride in the presence of ( N,N\| dimethylamino) pyridine(DMAP) and dicyclohexylcarbodimide (DCC).The results of the viscometry measurement,GPC and 1H\|NMR,elucidated that multiblock PLE copolymers with high content of short PEG segments( M n=2000) had been successfully obtained.The crystallinity of the copolymers was investigated by X\|ray diffraction.Mechanical testing showed that multiblock copolymers had relatively high tensile strength and large elongation.In a word,the measurements showed that the multiblock PLE copolymers had high content of short PEG segments( M n=2000),high molecular weight( M w～100,000),excellent hydrophilicity and mechanical properties.The results of cells cultured on the multiblock PLE copolymer indicated that it might be suitable to be utilized as cell scaffold for tissue engineering.
文摘High molecular weight up to 80×10 4 of poly(L lactide)(PLLA) was synthesized by bulk polymerization of L lactide using stannous octoate as initiator. The influence of polymerization time, temperature and initiator concentration on the molecular weight of PLLA was studied. An enhancement technique named fibrillated compression moulding has been developed for preparing high strength PLLA rods with bending strength of 20 260 MPa and shear strength of 170 190 MPa respectivity.
基金financially supported by the National Key Research and Development Program of China (Nos. 2017YFB0309301 and 2017YFB0309302)the Natural Science Foundation of Shanghai, China (No. 17ZR1407200)
文摘Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolymers and electrospun ultrafine fibers were investigated and compared with those of PLLA and PA4 blends. PLLA and PA4 were found incompatible and formed individual crystalline regions, along with reciprocal inhibition in crystallization. Electrospun fibers were highly hydrophobic, even if hydrophilic PA4 was the rich component. The crystallinity of either PLLA or PA4 decreased after electrospinning and PLLA-rich as-spun fibers were almost amorphous. Immersion tests proved that fibers of block copolymers were relatively homogeneous with micro-phase separation between PLLA and PA4. The fibrous structures of copolymers were different from those of the fibers electrospun from blends, for which sheath-core structure induced by macro-phase separation between homopolymers of PLLA and PA4 was confirmed by TEM, EDS, and XPS.
基金financially supported by the National Natural Science Foundation of China(Nos.5127319851373169+4 种基金510330035130317651321062 and 51403089)863 Program(No.2011AA02A202)from the Ministry of Science and Technology of ChinaInnovative Research Group(No.51321062)
文摘In this study, the poly（L-lactide）/poly（D-lactide） （PLLA/PDLA） blends with different optical purities of PLLA and various molecular weights of PDLA are prepared by solution mixing, and the stereocomplex formation and phase separation behaviors of these blends are investigated. Results reveal that optical purity and molecular weight do not vary the crystal structure of PLA stereocomplex （sc） and homochiral crystallites （hc）. As the optical purity increasing in the blends, the melting temperature of sc （Tsc） and the content of sc （AHsc） increased, while the melting temperature of hc （Thin） hardly changes, although the content ofhc （AHhm） decreased gradually. The Tsc and AHsc are also enhanced as the molecular weight of PDLA reduces, and the AHhm reduces rapidly even though the Thin does not vary apparently. With lower optical purities of PLLA and higher molecular weights of PDLA, three types of crystals form in the blends, i.e., PLA sc, PLLA hc and PDLA hc. As molecular weight decreases and optical purity enhances, the crystal phase decreases to two （sc and PDLA hc）, and one （sc） finally. This investigation indicates that the phase separation behavior between PLLA and PDLA in the PLLA/PDLA blends not only depends on molecular weights, but also relies on the optical purities of polymers.
