Siefker David, Chan Brandon A, Zhang Meng, Nho Ju-Woo, Zhang Donghui
Department of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Macromolecules. 2022 Apr 12;55(7):2509-2516. doi: 10.1021/acs.macromol.1c02472. Epub 2022 Mar 30.
Zwitterionic ring-opening polymerization (ZROP) of sarcosine-derived thiocarboxyanhydrides (Me-NNTAs) can be induced by using 1,1,3,3-tetramethylguanidine (TMG) initiators in CHCl at 25 °C, rapidly producing well-defined polysarcosine polymers with controlled molecular weights ( = 1.9-37 kg/mol) and narrow molecular weight distributions ( = 1.01-1.12). The reaction exhibits characteristics of a living polymerization, evidenced by pseudo-first-order polymerization kinetics, the linear increase of polymer molecular weight ( ) with conversion, and the successful chain extension experiments. The polymerization is proposed to proceed via propagating macro-zwitterions bearing a cationic 1,1,3,3-tetramethylguanidinium and an anionic thiocarbamate chain end. The TMG not only initiates the polymerization but also serves to stabilize the thiocarbamate chain end where the monomer addition occurs. Because of the enhanced hydrolytic stability of Me-NNTA, the polymerization can be conducted without the rigorous exclusion of moisture, further enhancing the appeal of the method to access well-defined polysarcosine.
在25°C的CHCl中，使用1,1,3,3-四甲基胍（TMG）引发剂可引发肌氨酸衍生的硫代羧酐（Me-NNTAs）的两性离子开环聚合（ZROP），快速生成分子量可控（ = 1.9 - 37 kg/mol）且分子量分布窄（ = 1.01 - 1.12）的结构明确的聚肌氨酸聚合物。该反应呈现活性聚合的特征，表现为假一级聚合动力学、聚合物分子量（ ）随转化率线性增加以及成功的链增长实验。该聚合反应被认为是通过带有阳离子1,1,3,3-四甲基胍鎓和阴离子硫代氨基甲酸酯链端的增长型大两性离子进行的。TMG不仅引发聚合反应，还用于稳定发生单体加成的硫代氨基甲酸酯链端。由于Me-NNTA的水解稳定性增强，聚合反应可以在不严格排除水分的情况下进行，进一步提高了该方法制备结构明确的聚肌氨酸的吸引力。
