Substantially Enhanced Stereocomplex Crystallization of Poly(L-lactide)/Poly(D-lactide) Blends by the Formation of Multi-Arm Stereo-Block Copolymers
Substantially Enhanced Stereocomplex Crystallization of Poly(L-lactide)/Poly(D-lactide) Blends by the Formation of Multi-Arm Stereo-Block Copolymers
复制标题
通过形成多臂立体嵌段共聚物显着增强聚(L-丙交酯)/聚(D-丙交酯)共混物的立体络合物结晶
DOI：
10.3390/cryst12020210
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发表时间：
2022-02-01
期刊：
影响因子：
2.7
通讯作者：
Bai, Hongwei
中科院分区：
文献类型：
--
作者：
Diao, Xingyuan;Chen, Xiaonan;Bai, Hongwei
立体配合物型聚乳酸（SC-PLA）是由聚l -丙交酯（PLLA）和聚d -丙交酯（PDLA）链在结晶状态下交替填充而成的，是一种日益流行的工程生物塑料，具有优异的水解稳定性和热机械性能。然而，通过熔融加工获得高分子量PLLA/PDLA共混物的高性能SC- pla产品是非常困难的，因为SC晶和均晶（hc）在熔融结晶过程中竞争性地形成。本文采用了一种简单而有效的方法，通过在反应熔融共混过程中向对映体共混物中引入微量的环氧基功能化小分子改性剂来促进SC的形成。结果表明，改性剂的环氧基与聚乳酸末端羟基之间的反应显著增强了多臂立体嵌段聚乳酸共聚物的形成。更令人印象深刻的是，有趣的是，仅引入0.5 wt%的改性剂就可以在等温和非等温熔体结晶中诱导共混物形成专属SC。突出的SC结晶性可能是由于这种独特的共聚物作为相容剂抑制了熔融状态下交替排列的PLLA/PDLA链段的分离。此外，这些共聚物的产生不会导致共混物熔体粘度的显著增加。这些发现为SC-PLA材料高通量加工成有用产品提供了新的机会。
Stereocomplex-type polylactide (SC-PLA) created by alternate packing of poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains in a crystalline state has emerged as a growingly popular engineering bioplastic that possesses excellent hydrolytic stability and thermomechanical properties. However, it is extremely difficult to acquire high-performance SC-PLA products via melt-processing of high-molecular-weight PLLA/PDLA blends because both SC crystallites and homocrystallites (HCs) are competitively formed in the melt-crystallization. Herein, a facile yet powerful way was employed to boost SC formation by introducing trace amounts of some epoxy-functionalized small-molecule modifiers into the enantiomeric blends during reactive melt-blending. The results show that the SC formation is considerably enhanced with the in situ generation of multi-arm stereo-block PLA copolymers, based on the reaction between epoxy groups of the modifiers and hydroxyl end groups of PLAs. More impressively, it is intriguing to find that the introduction of only 0.5 wt% modifiers can induce exclusive SC formation in the blends upon isothermal and non-isothermal melt-crystallizations. The outstanding SC crystallizability might be attributed to the suppressing effect of such unique copolymers on the separation of the alternately arranged PLLA/PDLA chain segments in molten state as a compatibilizer. Furthermore, the generation of these copolymers does not result in a significant increase in melt viscosity of the blends. These findings suggest new opportunities for the high-throughput processing of SC-PLA materials into useful products.