Ni Lingling, Xu Shanshan, Sun Chenxuan, Wang Bao, Zheng Ying, Yu Chengtao, Bao Yongzhong, Shan Guorong, Pan Pengju
College of Chemical and Biological Engineering, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China.
Institute of Zhejiang University-Quzhou, 99 Zheda Road, Quzhou 324000, China.
J Phys Chem Lett. 2023 Jun 8;14(22):5181-5187. doi: 10.1021/acs.jpclett.3c01102. Epub 2023 May 30.
The melting of semicrystalline polymers is a typical multistep process and involves a series of intermediate melt states. However, the structural characteristics of the intermediate polymer melt is unclear. Herein, we choose polymorphic -1,4-polyisoprene (PI) as a model polymer system and elucidate the structures of the intermediate polymer melt and their strong effects on the following crystallization process. We find that the metastable β crystals of the PI melt first into an intermediate state and then recrystallize in new crystals upon thermal annealing. The intermediate melt shows multilevel structural order at the chain level depending on the melting temperature. The conformationally ordered melt can memorize the initial crystal polymorph and accelerate the crystallization process, while the ordered melt without the conformational order can only enhance the crystallization rate. This work provides deep insight into the multilevel structural order of polymer melts and its strong memory effects on the crystallization process.
半结晶聚合物的熔融是一个典型的多步过程，涉及一系列中间熔体状态。然而，中间聚合物熔体的结构特征尚不清楚。在此，我们选择多晶型的-1,4-聚异戊二烯（PI）作为模型聚合物体系，阐明中间聚合物熔体的结构及其对后续结晶过程的强烈影响。我们发现，PI熔体的亚稳β晶体首先转变为中间状态，然后在热退火时再结晶形成新的晶体。中间熔体在链水平上表现出取决于熔融温度的多级结构有序性。构象有序的熔体可以记住初始晶体多晶型并加速结晶过程，而没有构象有序的有序熔体只能提高结晶速率。这项工作深入洞察了聚合物熔体的多级结构有序性及其对结晶过程的强烈记忆效应。
