Shi Yunxiang, Li Jingqing, Li Hongfei, Zhang Bin, Christiansen Jesper de Claville, Yu Donghong, Jiang Shichun
School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China.
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China.
Soft Matter. 2024 May 29;20(21):4270-4281. doi: 10.1039/d4sm00225c.
Chain flexibility or stiffness based polymer conformation plays a crucial role in affecting the dynamics and kinetics of polymers, which is related to the hierarchical architecture of chains. A series of random copolymers of ethylene and 1-alkenes including 1-hexene, 1-octene, and 1-dodecene were synthesized with metallocene catalysts. The crystallization behavior and memory effect in random ethylene-1-alkene copolymers with different side groups were investigated differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). Rheological tests were performed for understanding their dynamical behavior. The results show that the melting peak and the viscosity decrease but the orthorhombic crystal dimensions increase with co-unit contents increasing in the copolymers. It was found that the scaling relationship between the zero shear viscosity () and molecular weight () of the copolymers containing ethylene-1-hexene and ethylene-1-octene is 3.6, which is higher than the classical scaling value of 3.4. The memory of crystals in the melt is enhanced with the increase of 1-alkene contents but is independent of the types of 1-alkenes. The enhanced melt memory effect in the copolymers was proposed due to the effect of the 1-alkene based side groups on the dynamics of polymer chains. The present work would be helpful to understand the chain stiffness based polymer dynamics and processing of polyolefins and copolymers prepared with the metallocene catalyst.
基于链柔性或刚性的聚合物构象在影响聚合物的动力学和动力学过程中起着至关重要的作用，这与链的层次结构有关。用茂金属催化剂合成了一系列乙烯与1-烯烃的无规共聚物，包括1-己烯、1-辛烯和1-十二碳烯。采用差示扫描量热法（DSC）和广角X射线散射法（WAXS）研究了具有不同侧基的无规乙烯-1-烯烃共聚物的结晶行为和记忆效应。进行流变学测试以了解它们的动态行为。结果表明，随着共聚物中共单元含量的增加，熔点和粘度降低，但正交晶尺寸增大。发现含乙烯-1-己烯和乙烯-1-辛烯的共聚物的零剪切粘度（）与分子量（）之间的标度关系为3.6，高于经典标度值3.4。熔体中晶体的记忆随着1-烯烃含量的增加而增强，但与1-烯烃的类型无关。由于基于1-烯烃的侧基对聚合物链动力学的影响，提出了共聚物中增强的熔体记忆效应。本工作将有助于理解基于链刚性的聚烯烃和用茂金属催化剂制备的共聚物的动力学和加工过程。
