Gao Tianle, Xia Xiaochao, Watanabe Tomohisa, Ke Chun-Yao, Suzuki Ryota, Yamamoto Takuya, Li Feng, Isono Takuya, Satoh Toshifumi
Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Division of Applied Chemistry, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
J Am Chem Soc. 2024 Sep 11;146(36):25067-25077. doi: 10.1021/jacs.4c08009. Epub 2024 Jul 31.
The sequence of monomers within a polymer chain plays a pivotal role in determining the physicochemical properties of the polymer. In the copolymerization of two or more monomers, the arrangement of monomers within the resulting polymer is primarily dictated by the intrinsic reactivity of the monomers. Precisely controlling the monomer sequence in copolymerization, particularly through the manipulation of catalysts, is a subject of intense interest and poses significant challenges. In this study, we report the catalyst-controlled copolymerization of epoxides, -tosyl aziridine (TAz), and cyclic anhydrides. To achieve this, a binary catalyst system comprising a Lewis acid, triethylborane, and Brønsted base, -BuP, was utilized. This system was utilized to regulate the selectivity between two catalytic reactions: ring-opening alternating copolymerization (ROAC) of epoxides/cyclic anhydrides and ROAC of TAz/cyclic anhydrides. Changing the catalyst ratio made it possible to continuously modulate the resulting poly(ester-amide ester) from ABA-type real block copolymers to gradient, random-like, reversed gradient, and reversed BAB-type block-like copolymers. A range of epoxides and anhydrides was investigated, demonstrating the versatility of this polymerization system. Additionally, density functional theory calculations were conducted to enhance our mechanistic understanding of the process. This synthetic method not only provides a versatile means for producing copolymers with comparable chemical compositions but also facilitates the exploration of the intricate relationship between monomer sequences and the resultant polymer properties, offering valuable insights for advancements in polymer science.
聚合物链中单体的序列在决定聚合物的物理化学性质方面起着关键作用。在两种或更多种单体的共聚反应中，所得聚合物中单体的排列主要由单体的固有反应性决定。精确控制共聚反应中的单体序列，尤其是通过催化剂的调控，是一个备受关注且极具挑战性的课题。在本研究中，我们报道了环氧化物、对甲苯磺酰氮丙啶（TAz）和环状酸酐的催化剂控制共聚反应。为此，使用了一种由路易斯酸三乙基硼和布朗斯特碱叔丁醇钾组成的二元催化剂体系。该体系用于调节两种催化反应之间的选择性：环氧化物/环状酸酐的开环交替共聚（ROAC）和TAz/环状酸酐的ROAC。改变催化剂比例使得能够将所得的聚（酯 - 酰胺酯）从ABA型真正的嵌段共聚物连续调节为梯度、类无规、反梯度和反BAB型嵌段状共聚物。研究了一系列环氧化物和酸酐，证明了该聚合体系的通用性。此外，还进行了密度泛函理论计算以加深我们对该过程机理的理解。这种合成方法不仅为制备具有可比化学组成的共聚物提供了一种通用手段，还促进了对单体序列与所得聚合物性能之间复杂关系的探索，为聚合物科学的发展提供了有价值的见解。
