结晶调节手性聚合物的立体复合材料：以聚乳酸为例《Accounts of Materials Research》

Stereocomplexed Materials of Chiral Polymers Tuned by Crystallization: A Case Study on Poly(lactic acid)

Ying Zheng, Shanshan Xu, Chengtao Yu, and Pengju Pan*

State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China

Institute of Zhejiang University-Quzhou, Quzhou 324000, China

Acc. Mater. Res. 2022, XXXX, XXX, XXX-XXX

Publication Date: October 27, 2022

https://doi.org/10.1021/accountsmr.2c00208

Abstract

Conspectus

Widespread in chemistry and biochemistry, chirality strongly affects the biological, chemical, material, and physical properties. As a downstream derivative, the enantiopure polymers of opposite chirality can cocrystallize in the stereocomplex (SC) in their enantiomeric blends or block copolymers, which endows the materials with improved physical properties and specific functions such as enhanced melting temperature, thermal stability, crystallizability, and hydrolytic resistance. A well-studied stereocomplexable polymer is poly(lactic acid) (PLA); both of its two enantiomers, poly(l-lactic acid) and poly(d-lactic acid), are biobased and biodegradable. SC crystallization is a simple and practical approach to improve the essential properties and functions of chiral polymers, which advances existing polymer applications and paves a new way to develop a variety of novel materials. However, it is noteworthy that not all of the enantiomeric blends of l- and d-polymers can exclusively crystallize into SC crystals in a typical crystallization process, which is usually accompanied by the homocrystallization of each individual enantiomer. Developing stereocomplexed materials with controlled crystalline structure, physical properties, and functions is still challenging. Consequently, studying and discussing the stereocomplexed materials developed by harnessing SC crystallization are of fundamental importance not only to obtain novel functional materials but also to promote the advancement of material researches.

In this Account, we concisely summarize and analyze our recent progresses in SC crystallization and stereocomplexed materials of PLA, which initializes a conceptual methodology to study and develop the stereocomplexed materials from chiral polymers. We first introduce various approaches for controlling the polymorphic crystallization structure, in order to promote the SC crystallization of high-molecular-weight PLA and to prepare the stereocomplexed materials. Then, we present our efforts on the preparation of novel stereocomplexed materials such as micelles, physical hydrogels, and elastomers by harnessing SC crystallization. These stereocomplexed materials show good physical properties (e.g., thermomechanical property and thermal resistance) and can further be functionalized toward shape memory, drug release, and thermoresponsive materials. These works have established a practical platform to unveil the relationships between crystalline structure, physical properties, and functions of stereocomplexed materials. At the end of the Account, we offer a brief summary and outlooks in this field. Even though a case study on PLA is focused in this Account, a similar methodology can be generalizable to other chiral polymer systems. We hope that this Account will evoke new inspirations and innovative work in the field of stereocomplexed materials of chiral polymers in the near future.

SUBJECTS:

• Copolymers,

• Crystallization,

• Hydrogels,

• Materials,

• Polymers

摘要

纲要

手性在化学和生物化学中广泛存在，它强烈影响生物、化学、材料和物理性质。作为下游衍生物，手性相反的对映体纯聚合物可以在其对映体共混物或嵌段共聚物中的立体络合物（SC）中共结晶，这使材料具有改进的物理性能和特定功能，如提高的熔融温度、热稳定性、结晶性和抗水解性。一种研究良好的立体络合聚合物是聚乳酸（PLA）；它的两种对映体，聚（l-乳酸）和聚（d-乳酸），都是生物基和可生物降解的。SC结晶是改善手性聚合物基本性质和功能的一种简单实用的方法，它促进了现有的聚合物应用，为开发各种新型材料铺平了新的道路。然而，值得注意的是，并非所有l-和d-聚合物的对映体共混物都可以在典型的结晶过程中结晶成SC晶体，这通常伴随着各个对映体的均结晶。开发具有可控晶体结构、物理性质和功能的立体复合材料仍然具有挑战性。因此，研究和讨论利用SC结晶开发的立体复合材料不仅对于获得新的功能材料，而且对于促进材料研究的进展具有重要意义。

在这篇文章中，我们简要总结和分析了我们在SC结晶和PLA立体复合材料方面的最新进展，这为研究和开发手性聚合物立体复合材料奠定了概念方法。我们首先介绍了控制多晶型结晶结构的各种方法，以促进高分子量聚乳酸的SC结晶并制备立体复合材料。然后，我们介绍了我们通过利用SC结晶制备新型立体复合材料的努力，如胶束、物理水凝胶和弹性体。这些立体复合材料显示出良好的物理性能（例如，热机械性能和耐热性），并可进一步功能化为形状记忆、药物释放和热响应材料。这些工作为揭示立体复合材料的晶体结构、物理性质和功能之间的关系建立了一个实用平台。在描述末尾，我们提供了该领域的简要总结和展望。尽管本报告重点介绍了PLA的案例研究，但类似的方法也可推广到其他手性聚合物体系。我们希望该描述将在不久的将来唤起手性聚合物立体复合材料领域的新灵感和创新工作。