Bao Jianna, Xue Xiaojia, Li Kai, Chang Xiaohua, Xie Qing, Yu Chengtao, Pan Pengju
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
The Institute of Oil and Gas Technology of Changqing Oilfield Company , Xi'an 710018, China.
J Phys Chem B. 2017 Jul 20;121(28):6934-6943. doi: 10.1021/acs.jpcb.7b03287. Epub 2017 Jul 5.
Promoting the stereocomplexation ability of high-molecular-weight poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) is an efficient way to improve the thermal resistance of the resulting materials. Herein, we studied the competing crystallization kinetics, polymorphic crystalline structure, and lamellae structure of the PLLA/PDLA component in its miscible blends with poly(vinyl acetate) (PVAc) and proposed a method to improve the stereocomplexation ability of PLLA and PDLA through miscible blending with the other polymer. Crystallization of the PLLA/PDLA component is suppressed after the addition of PVAc, due to the dilution effect. The stereocomplexation ability of PLLA and PDLA is enhanced by blending with PVAc; this becomes more obvious at a high PVAc content (≥50 wt %) but less significant with the further increase of PLLA, PDLA molecular weights. Almost exclusive formation of SCs is achieved for PLLA and PDLA after blending with a large proportion of PVAc (e.g., 75 wt %). Incorporation of PVAc also facilitates the HC-to-SC structural reorganization upon heating. The increased chain mobility, decreased equilibrium melting point, and enhanced intermolecular interactions may account for the preferential stereocomplexation in PLLA/PDLA/PVAc blends.
提高高分子量聚（L-乳酸）（PLLA）和聚（D-乳酸）（PDLA）的立体复合能力是提高所得材料耐热性的有效方法。在此，我们研究了PLLA/PDLA组分与聚醋酸乙烯酯（PVAc）的互溶共混物中的竞争结晶动力学、多晶晶体结构和片晶结构，并提出了一种通过与其他聚合物互溶共混来提高PLLA和PDLA立体复合能力的方法。由于稀释效应，添加PVAc后PLLA/PDLA组分的结晶受到抑制。PLLA和PDLA与PVAc共混后立体复合能力增强；在高PVAc含量（≥50 wt%）时这种增强变得更加明显，但随着PLLA、PDLA分子量的进一步增加，这种增强效果不太显著。与大量PVAc（如75 wt%）共混后，PLLA和PDLA几乎完全形成立体复合物。加入PVAc还促进了加热时HC到SC的结构重组。链迁移率增加、平衡熔点降低以及分子间相互作用增强可能是PLLA/PDLA/PVAc共混物中优先形成立体复合物的原因。
