Polymers can undergo mechanochemical chain scission during ball-mill grinding (BMG). Various milling and polymer parameters were known to influence chain scission, but the influence of crystallinity was not fully explored. In this report, using ring-opening polymerization, we prepared a library of poly(lactide)s (PLAs) with varying molecular weight and varying crystallinity by changing the stereochemistry of monomers. Semicrystalline PLLA and PDLA (from l- and d-lactide, respectively), amorphous PLDLA (from a copolymerization of l- and d-lactide), and a stereocomplex between PLLA and PDLA were subjected to degradation experiments to assess their degradation kinetics. We found degradation rate constant trends that suggested that the crystallinity had a negligible influence on degradation rates. We attributed this behavior to the fast amorphization of the semicrystalline PLAs. This work provides important insight into how other polymer transformations that occur during ball milling can influence chain scission.

中文翻译：

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结晶度对球磨机研磨中聚丙交酯机械化学降解的影响


聚合物在球磨机研磨 （BMG） 过程中会发生机械化学链断裂。已知各种研磨和聚合物参数会影响链断裂，但结晶度的影响尚未得到充分探讨。在本报告中，使用开环聚合，我们通过改变单体的立体化学制备了具有不同分子量和不同结晶度的聚（丙交酯）（PLA）库。对半结晶 PLLA 和 PDLA（分别来自 l-和 d-丙交酯）、无定形 PLDLA（来自 l-和 d-丙交酯的共聚）以及 PLLA 和 PDLA 之间的立体复合物进行了降解实验，以评估它们的降解动力学。我们发现降解速率常数趋势表明结晶度对降解速率的影响可以忽略不计。我们将这种行为归因于半结晶 PLA 的快速非晶化。这项工作为球磨过程中发生的其他聚合物转变如何影响链断裂提供了重要的见解。