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
Gamma-ray radiation has always been a convenient and effective way to modify the inter- facial properties in polymer blends. In this work, a small amount of trimethylolpropane triacrylate （TMPTA） was incorporated in...Gamma-ray radiation has always been a convenient and effective way to modify the inter- facial properties in polymer blends. In this work, a small amount of trimethylolpropane triacrylate （TMPTA） was incorporated into poly（ethylene terephthalate） （PET）/random terpolymer elastomer （ST2000） blends by melt-blending. The existence of TMPTA would induce the crosslinking of PET and ST2000 molecular chains at high temperatures of blend- ing, resulting in the improvement in the impact strength but the loss in the tensile strength. When the PET/ST2000 blends were irradiated by gamma-ray radiation, the integrated me- chanical properties could be enhanced significantly at a high absorbed dose. The irradiated sample at a dose of 100 kGy even couldn＇t be broken under the impact test load, and at the same time, has nearly no loss of tensile strength. Based on the analysis of the impact- fractured surface morphologies of the blends, it can be concluded that gamma-ray radiation at high absorbed dose can further in situ enhance the interfacial adhesion by promoting the crosslinking reactions of TMPTA and polymer chains. As a result, the toughness and strength of PET/ST2000 blend could be dramatically improved. This work provides a facial and practical way to the fabrication of polymer blends with high toughness and strength.展开更多
Nanomicelles,self-assembling nanosized particles with a hydrophobic core and hydrophilic shell,are currently successfully used as carriers for targeted drug delivery systems via the enhanced permeability and retention...Nanomicelles,self-assembling nanosized particles with a hydrophobic core and hydrophilic shell,are currently successfully used as carriers for targeted drug delivery systems via the enhanced permeability and retention（EPR） effect at the tumor sites.In this study,a near-infrared fluorescent cyanine dye（Cy7-NHS） was conjugated to poly（ethylene glycol）-block-poly（ε-caprolactone）（NH 2-PEG-b-PCL）,and the resulting Cy7-PEG-PCL was further mixed with mPEG-b-PCL to form nanomicelles as carriers for paclitaxel（PTX） delivery.Our results showed that the selected mPEG 4000-b-PCL 2500 copolymers self-assembled to form stable micelles with an average size of 30 nm in diameter and a zeta potential of approximately-3 mV.The micelles also exhibited more than 95% encapsulation efficiency of PTX when the molar ratio between paclitaxel and copolymers was 1/4.In vitro cytotoxicity study showed that the PTX-loaded nanomicelles had a similar cell growth inhibition efficacy to that of Taxol against human breast cancer MCF-7 cells.In vivo imaging showed that the Cy7-labeled nanomicelles could be passively targeted to tumor sites effectively after intravenous injection via the tail vein.Also,a strong anti-tumor activity was observed in the nude mice xenografted MCF-7 breast tumor after treatment with PTX-loaded micelles,similar to that of Taxol.As a result,the micelle drug delivery system designed in this paper has great potential in targeted imaging of tumors and chemotherapy.展开更多
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.
文摘Gamma-ray radiation has always been a convenient and effective way to modify the inter- facial properties in polymer blends. In this work, a small amount of trimethylolpropane triacrylate （TMPTA） was incorporated into poly（ethylene terephthalate） （PET）/random terpolymer elastomer （ST2000） blends by melt-blending. The existence of TMPTA would induce the crosslinking of PET and ST2000 molecular chains at high temperatures of blend- ing, resulting in the improvement in the impact strength but the loss in the tensile strength. When the PET/ST2000 blends were irradiated by gamma-ray radiation, the integrated me- chanical properties could be enhanced significantly at a high absorbed dose. The irradiated sample at a dose of 100 kGy even couldn＇t be broken under the impact test load, and at the same time, has nearly no loss of tensile strength. Based on the analysis of the impact- fractured surface morphologies of the blends, it can be concluded that gamma-ray radiation at high absorbed dose can further in situ enhance the interfacial adhesion by promoting the crosslinking reactions of TMPTA and polymer chains. As a result, the toughness and strength of PET/ST2000 blend could be dramatically improved. This work provides a facial and practical way to the fabrication of polymer blends with high toughness and strength.
基金National Basic Research Program of China (973Program,Grant No. 2007CB935800 and 2009CB930300)Program forNew Drug R&D (Grant No. 2009ZX09310-001)+2 种基金NSFC projects(Grant No. 81072597)Beijing NSF project (Grant No. 7112089)Programs from Ministry of Education (Grant No. BMU20110268and BMU20110263)
文摘Nanomicelles,self-assembling nanosized particles with a hydrophobic core and hydrophilic shell,are currently successfully used as carriers for targeted drug delivery systems via the enhanced permeability and retention（EPR） effect at the tumor sites.In this study,a near-infrared fluorescent cyanine dye（Cy7-NHS） was conjugated to poly（ethylene glycol）-block-poly（ε-caprolactone）（NH 2-PEG-b-PCL）,and the resulting Cy7-PEG-PCL was further mixed with mPEG-b-PCL to form nanomicelles as carriers for paclitaxel（PTX） delivery.Our results showed that the selected mPEG 4000-b-PCL 2500 copolymers self-assembled to form stable micelles with an average size of 30 nm in diameter and a zeta potential of approximately-3 mV.The micelles also exhibited more than 95% encapsulation efficiency of PTX when the molar ratio between paclitaxel and copolymers was 1/4.In vitro cytotoxicity study showed that the PTX-loaded nanomicelles had a similar cell growth inhibition efficacy to that of Taxol against human breast cancer MCF-7 cells.In vivo imaging showed that the Cy7-labeled nanomicelles could be passively targeted to tumor sites effectively after intravenous injection via the tail vein.Also,a strong anti-tumor activity was observed in the nude mice xenografted MCF-7 breast tumor after treatment with PTX-loaded micelles,similar to that of Taxol.As a result,the micelle drug delivery system designed in this paper has great potential in targeted imaging of tumors and chemotherapy.
