Enantiomeric blends of L- and D-type chiral polymers usually show distinct crystallization behavior and physical properties from the corresponding enantiopure polymers. However, the crystallization kinetics and crystalline structure of the enantiomeric blends of L- and D-polymers are not yet well understood, particularly concerning the chiral polymers with low chiral moiety densities. Herein, we synthesized a series of long-spaced chiral polyesters with a relatively low chiral moiety content and investigated the effects of enantiomeric blending on the crystallization kinetics and crystal polymorphism of chiral polyesters. Different from the other chiral polyesters with high chiral moiety content, the enantiomeric blends of long-spaced chiral polyesters do not crystallize into the new stereocomplex crystals but have a faster crystallization rate than the corresponding enantiopure polyesters. Compared to the enantiopure polyesters, the enantiomeric blends show the preferred formation of thermally stable form-I crystals in the cooling process and the broader temperature range for generating the form-I crystals in isothermal crystallization. The effects of enantiomeric blending on crystallization become less obvious with decreasing the chiral moiety content or increasing the methylene spacer length. We infer that the accelerated crystallization and facilitated formation of form-I crystals in enantiomeric blends are correlated with the interchain interactions between L- and D-polyesters. This study provides new insights into the crystallization of long-spaced chiral polyesters.

中文翻译：

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在长间距手性聚酯的对映体共混物中加速结晶和优先形成热稳定晶相


L 型和 D 型手性聚合物的对映体共混物通常表现出与相应的对映体纯聚合物不同的结晶行为和物理性质。然而，L 和 D 聚合物的对映体共混物的结晶动力学和晶体结构尚不清楚，特别是关于具有低手性部分密度的手性聚合物。在此，我们合成了一系列手性部分含量相对较低的长间距手性聚酯，并研究了对映体共混对手性聚酯结晶动力学和晶体多晶型性的影响。与其他具有高手性基团含量的手性聚酯不同，长间距手性聚酯的对映体共混物不会结晶成新的立体复合物晶体，但比相应的对映体纯聚酯具有更快的结晶速率。与对映体纯聚酯相比，对映体共混物在冷却过程中显示出热稳定的 I 型晶体的优先形成，并且在等温结晶中产生 I 型晶体的温度范围更宽。对映体共混对结晶的影响随着手性部分含量的降低或亚甲基间隔区长度的增加而变得不那么明显。我们推断，对映体混合物中 I 型晶体的加速结晶和促进形成与 L-和 D-聚酯之间的链间相互作用相关。本研究为长间距手性聚酯的结晶提供了新的见解。