Crystallization of Star-Shaped Poly(L-lactide)s with Arm Chains Aligned in the Same Direction in Two-Dimensional Crystals in a Langmuir Monolayer
Crystallization of Star-Shaped Poly(L-lactide)s with Arm Chains Aligned in the Same Direction in Two-Dimensional Crystals in a Langmuir Monolayer
复制标题
朗缪尔单层二维晶体中臂链同向排列的星形聚（L-丙交酯）的结晶
DOI：
10.1021/acs.langmuir.3c00199
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发表时间：
2023
期刊：
影响因子：
3.9
通讯作者：
Kumaki Jiro
中科院分区：
文献类型：
--
作者：
Yamazaki Shota;Harada Mahoko;Watanabe Yuya;Lang Rongjian;Kato Takashi;Haba Osamu;Fukushima Kazuki;Kumaki Jiro
聚丙交酯 (PLA) 在朗缪尔单层中结晶形成长链晶体，因为结晶在水面上加速。这是一种独特的情况，可以通过简单地测量层状厚度来分析链堆积。在此，通过l-丙交酯与各种多元醇作为引发剂的聚合合成了具有2-12臂的星形聚(l-丙交酯)(PLLAs)，并通过原子力显微镜研究了它们在单层中的结晶行为。 PLLA 包含 2-4 个结晶臂，所有臂均沿同一方向排列，并在中央多元醇单元处折叠。同时，包含 6 和 12 个臂的 PLLA 结晶，两半臂从中心向相反方向延伸，这很可能是由于拥挤的臂的空间阻碍。考虑到 PLLA 在压缩过程中从一次形成的凝聚非晶态结晶，因此它们具有强烈的结晶倾向，且臂排列在同一方向。据了解，即使臂的数量只有2个，星形PLA的结晶率也会比线性PLA降低。这应该与臂排列在同一方向的星形PLLA的独特结晶行为密切相关。
Polylactide (PLA) crystallizes to form extended-chain crystals in a Langmuir monolayer because crystallization is accelerated on the water surface. This is a unique situation where chain packing can be analyzed by simply measuring the lamellar thickness. Herein, star-shaped poly(l-lactide)s (PLLAs) with 2–12 arms were synthesized through the polymerization ofl-lactide with various polyols as initiators, and their crystallization behavior in a monolayer was studied via atomic force microscopy. The PLLAs comprising 2–4 arms crystallized with all arms aligned in the same direction and being folded at the central polyol unit. Meanwhile, the PLLAs comprising 6 and 12 arms crystallized with both halves of the arms extended from the center to the opposite directions, most likely due to the steric hindrance of the crowded arms. Considering that the PLLAs crystallized from a once-formed condensed amorphous state during compression, they have a strong tendency to crystallize with the arms aligned in the same direction. The crystallization rate of star-shaped PLAs is known to reduce compared with that of a linear PLA even if the number of arms is as few as 2. This should be closely related to the unique crystallization behavior of the star-shaped PLLAs with the arms aligned in the same direction.