School of Materials Science and Engineering, Sun Yat-sen University, No. 135, Xingang Xi Road, Guangzhou 510275, China.
Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Sun Yat-sen University, No. 135, Xingang Xi Road, Guangzhou 510275, China.
ACS Macro Lett. 2022 Jun 21;11(6):792-798. doi: 10.1021/acsmacrolett.2c00210. Epub 2022 Jun 2.
Poly(ethylene glycol) (PEG) has been extensively used in diverse applications. However, it is not biodegradable and shows abnormal immune responses. Herein, a fast, controlled, ring-opening polymerization (ROP) of 2-oxo-15-crown-5 (O-15C5) is reported to prepare well-defined PEG-like polyesters, poly(O-15C5). This approach relies on a coordination between the macrocyclic monomer and Na that increases the electrophilicity of the carbonyl group of O-15C5 and leads to a fast controlled ROP (dispersity, < 1.2). Both computational and mechanistic studies show that the selective Na binding to the monomer over poly(O-15C5) allows the ring-opening initiation and propagation to be more energetically favorable than side transesterifications. This is the key to control the challenging entropy-driven ROP of O-15C5. Moreover, with the aid of Na and organic base, poly(O-15C5) depolymerized readily into O-15C5 in 2 h. Also, it degraded in a buffer of pH 7.4 by hydrolysis.
聚乙二醇（PEG）已广泛应用于各种领域。然而，它不可生物降解，并表现出异常的免疫反应。在此，我们报道了一种快速、可控的 2-氧代-15-冠-5（O-15C5）开环聚合（ROP）反应，以制备具有明确结构的聚乙二醇类似聚酯，聚（O-15C5）。这种方法依赖于大环单体与 Na 的配位，增加了 O-15C5 中羰基的亲电性，从而导致快速可控的 ROP（分散度，<1.2）。计算和机理研究均表明，Na 对单体的选择性结合优先于聚（O-15C5）的侧酯交换，这使得开环引发和增长比侧酯交换更具能量优势。这是控制 O-15C5 这一具有挑战性的熵驱动 ROP 的关键。此外，在 Na 和有机碱的帮助下，聚（O-15C5）在 2 小时内迅速解聚为 O-15C5。同时，它在 pH 值为 7.4 的缓冲液中通过水解降解。
