Zou Jiong, Fan Jingwei, He Xun, Zhang Shiyi, Wang Hai, Wooley Karen L
Department of Chemistry and Department of Chemical Engineering, Texas A&M University, P. O. Box 30012, 3255 TAMU, College Station, TX 77842 (USA).
Macromolecules. 2013 May 28;46(10):4223-4226. doi: 10.1021/ma4007939.
A facile N flow-accelerated -carboxyanhydride ring opening polymerization (NCA ROP) is demonstrated, herein, with rigorous kinetic studies to evaluate the methodology in detail. By using -hexylamine as initiator and γ-benzyl-L-glutamate -carboxyanhydride (BLG-NCA) as monomer, the NCA ROP a normal amine mechanism (NAM) reached 90% conversion in 2 h under N flow at room temperature in a fume hood, much shorter than the time required for the same polymerization conducted in a glove box (14 h). The efficient removal of CO from the reaction by N flow drove the carbamic acid-amine equilibrium toward the formation of active nucleophilic amino termini and promoted polymerization. The detailed kinetic studies of the polymerization with different feed ratios and N flow rates were conducted, demonstrating the living feature of the NCA ROP and the tuning of the polymerization rate by simply changing the flow rate of N. Maintenance of the reactivity of the amino ω-chain terminus and control during a subsequent polymerization were confirmed by performing chain extension reactions. The N flow method provides a new straightforward strategy to synthesize well-defined polypeptides with predictable molecular weights and narrow molecular weight distributions (PDI < 1.19).
本文展示了一种简便的氮气流加速的γ-羧基环酸酐开环聚合反应（NCA ROP），并进行了严格的动力学研究以详细评估该方法。以正己胺为引发剂，γ-苄基-L-谷氨酸γ-羧基环酸酐（BLG-NCA）为单体，在通风橱中室温下氮气氛围下，通过正常胺机理（NAM）的NCA ROP在2小时内转化率达到90%，比在手套箱中进行相同聚合反应所需的时间（14小时）短得多。氮气气流有效地去除了反应中的二氧化碳，使氨基甲酸-胺平衡朝着形成活性亲核氨基末端的方向移动，从而促进了聚合反应。对不同进料比和氮气流量的聚合反应进行了详细的动力学研究，证明了NCA ROP的活性特征以及通过简单改变氮气流量来调节聚合速率。通过进行链延伸反应，证实了氨基ω-链末端的反应活性在后续聚合过程中得以保持和控制。氮气气流法为合成具有可预测分子量和窄分子量分布（PDI < 1.19）的明确多肽提供了一种新的直接策略。
