Zhang Xiuhui, Dong Jing, Wang Feng, Zhang Xuequan, Liu Heng
Shandong Provincial College Laboratory of Rubber Material and Engineering/Key Laboratory of Rubber-Plastics, Ministry of Education, School of Polymer Science and Engineering, Qingdao University of Science & Technology, Qingdao 266042, China.
Petrochemical Research Institute, PetroChina, Beijing 102206, China.
Polymers (Basel). 2024 Sep 22;16(18):2672. doi: 10.3390/polym16182672.
The Nd-mediated coordinative chain transfer polymerization (CCTP) of dienes represents one of the state-of-the-art techniques in the current synthetic rubber field. Besides having well-controlled polymerization behaviors as well as high atom economies, it also allows for the generation of highly reactive Al-capped polydienyl chain-ends, which hold great potential, yet much less explored up to date, in achieving end functionalization to mimic the structure of natural rubber. In this study, we demonstrate an efficient in situ method to realize end-functionalizing polyisoprene by introducing epoxide compounds into a CCTP system. The end functionalization efficiency was 92.7%, and the obtained polymers were systematically characterized by H NMR, H,H-COSY NMR, DOSY NMR, and MALDI TOF. NMR studies revealed that a maximum of two EO units were introduced to the chain ends, and based on density functional theory (DFT) studies, an energy barrier of 33.3 kcal/mol was required to be overcome to open the ring of the EO monomer. Increasing the ratio of [Ip]/[Nd] resulted in gradually increased viscosities for the reaction medium and therefore gave rise to an end functionalization efficiency that decreased from 92.7% to 74.2%. The end hydroxyl group can also be readily converted to other functionalities, as confirmed by NMR spectroscopy.
钕介导的二烯烃配位链转移聚合（CCTP）是当前合成橡胶领域的先进技术之一。除了具有良好的可控聚合行为以及高原子经济性外，它还能生成具有高反应活性的铝封端聚二烯链端，这在实现端基官能化以模拟天然橡胶结构方面具有巨大潜力，但迄今为止探索较少。在本研究中，我们展示了一种通过将环氧化合物引入CCTP体系来实现聚异戊二烯端基官能化的高效原位方法。端基官能化效率为92.7%，并通过¹H NMR、¹H,¹H-COSY NMR、DOSY NMR和MALDI TOF对所得聚合物进行了系统表征。核磁共振研究表明，链端最多引入了两个环氧乙烷（EO）单元，基于密度泛函理论（DFT）研究，打开EO单体的环需要克服33.3 kcal/mol的能垒。[异戊二烯]/[钕]比例的增加导致反应介质的粘度逐渐增加，从而使端基官能化效率从92.7%降至74.2%。如核磁共振光谱所证实，端羟基也可轻松转化为其他官能团。
