Two poly(L-lactide)s (PLAs) with a degree of polymerization (DP) of 20 or 100 were prepared by trifluoroethanol-initiated ring-opening polymerization (ROP) catalyzed by tin(II) 2-ethyl hexanoate (SnOct2). These PLAs were annealed at 140 °C or at 160 °C in the presence of SnOct2, and the changes in topology and molecular weight distribution (MWD) were monitored by matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry and gel permeation chromatography (GPC). For the PLA with a DP 20, the main reaction was polycondensation combined with higher dispersities. In the case of the DP 100, PLA polycondensation was combined with disproportionation and the formation of a new MWD maximum around m/z 3500. In addition, extensive cyclization occurred, and the resulting cyclic PLAs crystallized separately from the linear chains in the form of extended ring crystals. These results also suggest that both extended chain and extended ring crystals posses the same crystal thickness as a result of thermodynamically controlled transesterification in the solid state.

中文翻译：

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固体聚（L-丙交酯）三氟乙酯的缩聚、环化和歧化反应以及同时形成长链晶体和长环晶体


在锡 （II） 2-乙基己酸酯 （SnOct2） 催化下，通过三氟乙醇引发的开环聚合 （ROP） 制备了两种聚合度 （DP） 为 20 或 100 的聚（L-丙交酯） （PLA）。这些 PLA 在 SnOct2 存在下在 140 °C 或 160 °C 下退火，并通过基质辅助激光解吸/电离飞行时间 （MALDI TOF） 质谱和凝胶渗透色谱 （GPC） 监测拓扑结构和分子量分布 （MWD） 的变化。对于使用 DP 20 的 PLA，主要反应是缩聚结合和更高的分散性。在 DP 100 的情况下，PLA 缩聚与歧化相结合，并在 m/z 3500 附近形成新的 MWD 最大值。此外，发生了广泛的环化，所得的环状 PLA 以延伸环状晶体的形式与线性链分开结晶。这些结果还表明，由于固态的热力学控制酯交换反应，长链晶体和长环晶体具有相同的晶体厚度。