Tacticity-Dependent Epitaxial Crystallization of Poly(l-lactic acid) on an Oriented Polyethylene Substrate,Macromolecules

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Tacticity-Dependent Epitaxial Crystallization of Poly(l-lactic acid) on an Oriented Polyethylene Substrate
Macromolecules ( IF 5.1 ) Pub Date : 2020-09-14 , DOI: 10.1021/acs.macromol.0c01456
Li Li _{1,

2} , Rui Xin ₃ , Huihui Li ₁ , Xiaoli Sun ₁ , Zhongjie Ren ₁ , Qigu Huang ₁ , Shouke Yan _{1,

3}

Affiliation

The influence of tacticity on the bulk crystallization and polyethylene (PE)-induced epitaxial crystallization of poly(l-lactic acid) (PLLA) was investigated. It was found that cold-crystallization of PLLA with different tacticities from the amorphous glassy state is easier than the melt-crystallization from the isotropic melt and the cold-crystallization of PLLA at the PE surface takes place earlier than in bulk. The time-lag between the PE-induced epitaxial crystallization and bulk cold-crystallization of PLLA increases with decreasing tacticity. For example, while the cold-crystallization of the PLLA sample with 95% tacticity in the bulk and at the PE surface starts almost simultaneously, the bulk cold-crystallization of PLLA with a tacticity of 89% starts at a time point where over 90% PLLA already crystallized epitaxially on the PE substrate. The almost simultaneous start of bulk and PE-induced cold-crystallization of high tacticity PLLA enables the creation of a cross-hatched lamellar structure, which is composed of PLLA lamellae oriented along the PE chain direction and tilted ca. 64° with respect to the PE chain direction. The big time-lag between PE-induced epitaxy and bulk cold-crystallization of low-tacticity PLLA results in the disappearance of tilted PLLA lamellae. This further confirms that the PLLA lamellae aligned in the chain direction of PE are caused by PE-induced epitaxial crystallization, whereas the tilt lamellae are caused by the homoepitaxy of PLLA based on the parallelism of the helical paths.

中文翻译：

定向聚乙烯基衬底上聚（l-乳酸）的立构规整外延结晶

立构规整度的大量结晶和聚乙烯（PE）的影响诱导聚外延结晶（升-乳酸（PLLA）。已经发现，具有与无定形玻璃态不同的立构规整度的PLLA的冷结晶比各向同性熔体的熔融结晶更容易，并且在PE表面的PLLA的冷结晶比本体发生的更早。PE诱导的外延结晶和PLLA的整体冷结晶之间的时滞随着立构规整度的降低而增加。例如，在本体中和在PE表面上，立构规整度为95％的PLLA样品几乎同时开始结晶，而立构规整度为89％的PLLA本体冷晶开始于超过90％的时间点。 PLLA已经在PE基板上外延结晶。高规整度PLLA的块体和PE诱导的冷结晶几乎同时开始，从而能够创建一个交叉阴影的层状结构，该结构由沿PE链方向定向并倾斜约ca的PLLA薄片组成。相对于PE链方向为64°。PE诱导的外延和低立构PLLA的大量冷结晶之间存在较大的时滞，导致倾斜的PLLA薄片消失。这进一步证实，沿PE链方向排列的PLLA薄片是由PE诱导的外延结晶引起的，而倾斜薄片是由PLLA的同质性基于螺旋路径的平行性引起的。PE诱导的外延和低立构PLLA的大量冷结晶之间存在较大的时滞，导致倾斜的PLLA薄片消失。这进一步证实，沿PE链方向排列的PLLA薄片是由PE诱导的外延结晶引起的，而倾斜薄片是由PLLA的同质性基于螺旋路径的平行性引起的。PE诱导的外延和低立构PLLA的大量冷结晶之间存在较大的时滞，导致倾斜的PLLA薄片消失。这进一步证实，沿PE链方向排列的PLLA薄片是由PE诱导的外延结晶引起的，而倾斜薄片是由PLLA的同质性基于螺旋路径的平行性引起的。

更新日期：2020-10-13

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