Polymer Chains Fold Prior to Crystallization
Polymer Chains Fold Prior to Crystallization
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DOI：
10.1021/acsmacrolett.1c00789
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发表时间：
2022-03-15
影响因子：
7.015
通讯作者：
Miyoshi, Toshikazu
中科院分区：
文献类型：
--
作者：
Jin, Fan;Yuan, Shichen;Miyoshi, Toshikazu
高分子链的结晶机理在分子水平上一直存在着争论：结晶过程中是先发生链折叠还是先形成层状结构？在这项研究中，我们报告的本地链轨迹的C-13-标记的半结晶聚合物在极端情况下的快速淬火的玻璃态，以及通过不同的途径从玻璃和熔体形成的结晶稳定的晶体。磁偶极相互作用不需要长程有序的分子对象，从而使我们能够跟踪局部链轨迹的聚合物链，即使在玻璃态。为了准确表征聚合物玻璃的局域链轨迹，采用扩展链构象重新考察了自然丰度对C-13-C-13双量子（DQ）核磁共振（NMR）信号的影响.结果表明，玻璃态链与熔融生长和冷生长的晶体具有相同的邻重入结构（邻重入数n = 1）。从这些结果，可以得出结论，（i）折叠发生在结晶和（ii）熔融和冷结晶不诱导额外的折叠，但在现有的模板进行聚合物链的重排。
There are long-standing debates in crystallization mechanism of polymer chains at the molecular levels: Which comes first, chain folding or lamellae formation during crystallization? In this study, we report the local chain trajectory of C-13-labeled semicrystalline polymer in an extreme case of rapidly quenched glassy state as well as thermodynamically stable crystals formed via different pathways from glass and melt. Magnetically dipole interactions do not require a long-range order of molecular objects and thus enable us to trace the local chain trajectory of polymer chains even in a glassy state. To accurately characterize the local chain trajectory of polymer glass, the natural abundance effect on C-13-C-13 double-quantum (DQ) nuclear magnetic resonance (NMR) signal is re-examined using extended chain conformation. As results, it is found that glassy chains adopt the same adjacent re-entry structure (adjacent re-entry number, n = 1) with the melt- and cold-grown crystals. From these results, it is concluded that (i) folding occurs prior to crystallization and (ii) melt and cold crystallization do not induce additional folding but proceed with rearrangements of polymer chains in the existing templates.