Tammann Analysis of the Molecular Weight Selection of Polymorphic Crystal Nucleation in Symmetric Racemic Poly(lactic acid) Blends
Tammann Analysis of the Molecular Weight Selection of Polymorphic Crystal Nucleation in Symmetric Racemic Poly(lactic acid) Blends
复制标题
对称外消旋聚乳酸共混物中多晶型晶体成核分子量选择的塔曼分析
DOI：
10.1021/acs.macromol.2c00457
复制
发表时间：
2022-04-14
期刊：
影响因子：
5.5
通讯作者：
Hu, Wenbing
中科院分区：
文献类型：
--
作者：
He, Yucheng;Liu, Dan;Hu, Wenbing
在对称外消旋聚乳酸（PLA）共混物中，高分子量使结晶度从立体络合物晶体转变为均晶。我们利用Flash DSC测量了具有5个分子量的对称外消旋PLA共混物的等温结晶动力学，并结合共聚焦拉曼光谱来鉴定其多晶相。结果证实结晶动力学是多晶晶体分子量选择的主要原因。低温区结晶成核动力学的Tammann分析表明，较高的分子量对均晶成核的影响较小；相反，它们抑制了立体络合物晶体的成核速率，使均晶占主导地位。高分子量聚合物中相邻单体的相关空穴解释了这一观察结果，这阻碍了有利于立体络合物晶体的交替外消旋聚合物的分子间成核。
High molecular weights switch the harvests of crystallinity from stereocomplex crystals to homocrystals in the symmetric racemic poly(lactic acid) (PLA) blends. We performed Flash DSC measurement of isothermal crystallization kinetics of symmetric racemic PLA blends with five molecular weights in combination with confocal Raman spectroscopy to identify their polymorphic crystal phases. The results confirmed crystallization kinetics as responsible for the molecular weight selection of polymorphic crystals. We further employed Tammann analysis on the crystal nucleation kinetics in the low-temperature region to reveal that higher molecular weights have little influence on homocrystal nucleation; rather, they suppress the nucleation rates of stereocomplex crystals, making homocrystals dominant. The observation was interpreted by the correlation hole of neighboring monomers among higher molecular weight polymers, which hinders intermolecular nucleation of alternatingly racemic polymers as favored for stereocomplex crystals.