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, Đ_M < 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.

中文翻译：

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2-Oxo-15-crown-5的催化控制开环聚合用于可降解和可回收的类PEG聚酯

聚（乙二醇）（PEG）已广泛用于各种应用。然而，它是不可生物降解的并且表现出异常的免疫反应。在此，据报道，2-oxo-15-crown-5 (O-15C5) 的快速、可控的开环聚合 (ROP) 可制备定义明确的 PEG 样聚酯聚 (O-15C5)。这种方法依赖于大环单体和 Na ⁺之间的配位，这增加了 O-15C5 的羰基的亲电性并导致快速控制 ROP（分散度，Đ _M < 1.2）。计算和机械研究均表明选择性 Na ⁺通过聚 (O-15C5) 与单体结合使得开环引发和传播比侧酯交换反应更积极。这是控制 O-15C5 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小时内很容易解聚成O-15C5。此外，它在 pH 7.4 的缓冲液中通过水解降解。