The molecular recyclability of poly (ethylene terephthalate) (PET) and three semi-aromatic polyesters poly (phloretic acid) (poly-H), poly (dihydroferulic acid) (poly-G), and poly (dihydrosinapinic acid) (poly-S) is e...The molecular recyclability of poly (ethylene terephthalate) (PET) and three semi-aromatic polyesters poly (phloretic acid) (poly-H), poly (dihydroferulic acid) (poly-G), and poly (dihydrosinapinic acid) (poly-S) is evaluated in this study. PET is an extensively used aromatic polyester, and poly-H, poly-G, and poly-S can be considered semi-aromatic poly (lactic acid) modifications. All these polyesters have been depolymerized at neutral pH and by acid- and base-catalyzed hydrolysis at two temperatures, i.e., 50˚C and 80˚C. Base-catalyzed depolymerization of virgin PET leads to an isolated yield of 38% after 48 hours of reaction at 80˚C. Contrary to these results for PET, almost all the monomers of the semi-aromatic polyesters poly-H, poly-G, and poly-S are recovered with isolated yields larger than 90% at the same temperature after 15 minutes in a facile manner. A shrinking particle model used to determine the global kinetics of the base-catalyzed depolymerization showed that the rate rises with increasing temperature. Using the shrinking particle model, the intrinsic reaction rate constants were determined. It has been demonstrated that the rate coefficients of the depolymerization of the semi-aromatic polyesters poly-H, poly-G, and poly-S are between 2 and 3 orders of magnitude higher than those for PET.展开更多
乳腺癌是目前世界范围内发病率最高的肿瘤,早发现、早诊断对于乳腺癌患者的治疗及预后具有重要意义。乳腺专用PET(dedicated breast PET,dbPET)是一种新兴的分子成像设备,在临床实践中用于乳腺癌的检测和肿瘤生物学的评估,具有比传统影...乳腺癌是目前世界范围内发病率最高的肿瘤,早发现、早诊断对于乳腺癌患者的治疗及预后具有重要意义。乳腺专用PET(dedicated breast PET,dbPET)是一种新兴的分子成像设备,在临床实践中用于乳腺癌的检测和肿瘤生物学的评估,具有比传统影像学手段更高的空间分辨率,可以识别乳房内放射性示踪剂摄取的详细形态学模式。鉴于国内外对dbPET的综合性分析较少,文章从dbPET在乳腺癌的筛查、诊断、摄取模式、新辅助化疗后评估及PET显像剂等方面的应用进行综述。展开更多
文摘The molecular recyclability of poly (ethylene terephthalate) (PET) and three semi-aromatic polyesters poly (phloretic acid) (poly-H), poly (dihydroferulic acid) (poly-G), and poly (dihydrosinapinic acid) (poly-S) is evaluated in this study. PET is an extensively used aromatic polyester, and poly-H, poly-G, and poly-S can be considered semi-aromatic poly (lactic acid) modifications. All these polyesters have been depolymerized at neutral pH and by acid- and base-catalyzed hydrolysis at two temperatures, i.e., 50˚C and 80˚C. Base-catalyzed depolymerization of virgin PET leads to an isolated yield of 38% after 48 hours of reaction at 80˚C. Contrary to these results for PET, almost all the monomers of the semi-aromatic polyesters poly-H, poly-G, and poly-S are recovered with isolated yields larger than 90% at the same temperature after 15 minutes in a facile manner. A shrinking particle model used to determine the global kinetics of the base-catalyzed depolymerization showed that the rate rises with increasing temperature. Using the shrinking particle model, the intrinsic reaction rate constants were determined. It has been demonstrated that the rate coefficients of the depolymerization of the semi-aromatic polyesters poly-H, poly-G, and poly-S are between 2 and 3 orders of magnitude higher than those for PET.
文摘乳腺癌是目前世界范围内发病率最高的肿瘤,早发现、早诊断对于乳腺癌患者的治疗及预后具有重要意义。乳腺专用PET(dedicated breast PET,dbPET)是一种新兴的分子成像设备,在临床实践中用于乳腺癌的检测和肿瘤生物学的评估,具有比传统影像学手段更高的空间分辨率,可以识别乳房内放射性示踪剂摄取的详细形态学模式。鉴于国内外对dbPET的综合性分析较少,文章从dbPET在乳腺癌的筛查、诊断、摄取模式、新辅助化疗后评估及PET显像剂等方面的应用进行综述。
