Crystallization of ultrathin films of polylactides: From chain chirality to lamella curvature and twisting
Crystallization of ultrathin films of polylactides: From chain chirality to lamella curvature and twisting
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DOI：
10.1021/ma071306u
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发表时间：
2008-03-11
期刊：
影响因子：
5.5
通讯作者：
Prud'homme, Robert E.
中科院分区：
文献类型：
--
作者：
Maillard, Damien;Prud'homme, Robert E.
用原位原子力显微镜在125 - 160 ℃之间跟踪了聚（D-丙交酯）（PDLA）和聚（L-丙交酯）（PLLA）在薄膜中的结晶（15 nm）。使用强制成核技术，观察到的边缘上的lamerations，显示出与聚合物手性的曲率。在PLLA的情况下，薄片是S形的，与Z形的PDLA薄片相反。在相同条件下结晶的PLLA和PDLA膜的TEM照片上也观察到这种行为，没有任何外部成核。如电子衍射图所示，两种对映体的晶体晶胞是相同的。首次建立了聚乳酸分子手性与宏观行为之间的关系。此外，可以链接到的方向的曲率的层流的聚（丙交酯）层流在带状球晶的扭曲的意义，和温度依赖性的曲率半径可以与消光环之间的距离。这些观察结果与基思和Padden的模型是一致的，因为弯曲的晶体在薄膜中可以被认为是“半lamps”，这给出了，当联合在一起，扭曲的完整lamps。
The crystallization Of poly(D-lactide) (PDLA) and poly(L-lactide) (PLLA) in ultrathin films (15 run) has been followed between 125 and 160 degrees C using in situ atomic force microscopy. Using a forced nucleation technique, edge-on lamellae were observed, showing a curvature which is related to the polymer chirality. In the case of PLLA, the lamellae are S-shaped, contrary to the PDLA lamellae which are Z-shaped. This behavior was also observed on TEM pictures of PLLA and PDLA films crystallized in the same conditions, without any external nucleation. As shown by electron diffraction patterns, the crystalline unit cells of the two enantiomers are identical. For the first time, a relationship has been established between the molecular chirality of poly(lactide)s and their macroscopic behavior. Moreover, the direction of curvature of the lamellae can be linked with the sense of twisting of the poly(lactide) lamellae in banded spherulites, and the temperature dependence of the radius Of Curvature can be correlated with the distance between the extinction rings. Those observations are consistent with Keith and Padden's model since the curved crystals in ultrathin films can be considered as "half-lamellae", which give, when associated together, twisted complete lamellae.