Role of Chain Entanglements in the Stereocomplex Crystallization between Poly(lactic acid) Enantiomers,ACS Macro Letters

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Role of Chain Entanglements in the Stereocomplex Crystallization between Poly(lactic acid) Enantiomers
ACS Macro Letters ( IF 5.1 ) Pub Date : 2021-07-21 , DOI: 10.1021/acsmacrolett.1c00394
Chenxuan Sun ₁ , Ying Zheng _{1,

2} , Shanshan Xu ₁ , Lingling Ni ₁ , Xing Li ₁ , Guorong Shan _{1,

2} , Yongzhong Bao _{1,

2} , Pengju Pan _{1,

2}

Affiliation

Stereocomplex (SC) crystallization between polymer enantiomers has opened a promising avenue for preparing high-performance materials. However, high-crystallinity SCs are difficult to achieve for high-molecular-weight (HMW) enantiomeric blends of chiral polymers [e.g., poly(lactic acid)]. Despite extensive studies, why HMW enantiomeric blends have difficulty in SC crystallization has not been clarified. Herein, we chose the HMW poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) 1/1 blend as the model system and demonstrated the crucial role of chain entanglement in regulating SC crystallization. PLLA/PDLA blends with various entanglement degrees were prepared by freeze-drying. We observed that disentangling promoted not only the crystallization rate but also the crystallinity of SCs in both the nonisothermal and isothermal processes. The less-entangled samples crystallized exclusively as the high-crystallinity SCs at different temperatures, in contrast to the predominant homocrystallization that occurred in the common entangled samples. This study provides deep insight into the SC crystallization mechanism of polymers and paves the way for future research attempting to prepare SC materials.

中文翻译：

链缠结在聚（乳酸）对映体之间的立体络合物结晶中的作用

聚合物对映异构体之间的立体络合物 (SC) 结晶为制备高性能材料开辟了一条有希望的途径。然而，对于手性聚合物[例如，聚(乳酸)]的高分子量(HMW)对映体共混物，难以实现高结晶度SC。尽管进行了广泛的研究，但为什么 HMW 对映体混合物难以 SC 结晶的原因尚未阐明。在此，我们选择了 HMW 聚（l-乳酸）/聚（d-乳酸) (PLLA/PDLA) 1/1 共混物作为模型体系，证明了链缠结在调节 SC 结晶中的关键作用。通过冷冻干燥制备具有不同缠结度的PLLA/PDLA共混物。我们观察到，在非等温和等温过程中，解开不仅提高了 SCs 的结晶速率，而且还提高了 SCs 的结晶度。与常见的纠缠样品中发生的主要同晶化相比，纠缠较少的样品在不同温度下仅结晶为高结晶度 SCs。该研究深入了解了聚合物的 SC 结晶机制，并为未来制备 SC 材料的研究铺平了道路。

更新日期：2021-08-17

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