The crystalline memory effect is frequently observed in polymer crystallization, but the melt structure remains unresolved. In this work, the preserved spherulites in the melt of poly(L-lactide)-based block copolymers are observed by polarized optical microscopy (POM) unexpectedly. These spherulites are not erased instantly on reaching the melting temperatures, but it takes tens of minutes at a designed melting temperature to completely erase the spherulites. These preserved spherulites in the melt, where some crystalline traces are lost but the Maltese cross appearance is still obvious, are possibly attributed to the long range of molecular orientation enhanced by microphase separation between two blocks. Moreover, these preserved spherulites have a significant effect on the subsequent crystallization, i.e. a faster radius growth rate and denser nucleation. This study highlights that a thermodynamically unstable structure can be fully preserved in a supercooled melt for a long time, which has never been reported elsewhere.

中文翻译：

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聚（L-丙交酯）基嵌段共聚物中的意外晶体记忆效应

在聚合物结晶中经常观察到晶体记忆效应，但熔体结构仍未解析。在这项工作中，出乎意料地通过偏振光学显微镜（POM）观察到了聚（L-丙交酯）基嵌段共聚物的熔体中保存的球晶。这些球晶在达到熔化温度时不会立即消失，但是在设计的熔化温度下要花费数十分钟才能完全消失。这些在熔体中保留的球晶丢失了一些晶体痕迹，但马耳他的十字形外观仍然很明显，这可能归因于两个嵌段之间的微相分离增强了分子取向的长距离范围。此外，这些保存的球晶对随后的结晶具有重要影响，即更快的半径生长速率和更密集的形核。这项研究强调，热力学不稳定的结构可以在过冷的熔体中长时间保存，这在其他地方从未有过报道。