A major success has been made on organocatalytic ring-opening alternating copolymerization (ROAP) of phthalic anhydride and ethylene oxide (EO) by use of a simple phosphazene base (t-BuP₁). Polyesters with perfectly alternating sequence distribution, controlled molar masses, and low dispersities (Đ_M < 1.1) are obtained. The ROAP exhibited a distinct living nature so that block, nonlinear, end-functional structures and postpolymerization modification of the alternating polyesters are readily achieved. Solvent, excess EO, and catalyst can be effortlessly recovered and reused. The ideally suitable basicity of t-BuP₁ is considered crucial for the high selectivity and neatness of the ROAP, which engenders a self-buffering mechanism rendering the carboxy and hydroxy terminals appropriately active to allow chain growth in an strictly alternating manner and complete avoidance of side reactions (epoxide self-propagation, transesterification) even at full conversion of the anhydride.

中文翻译：

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自缓冲有机催化剪裁交替聚酯

通过使用简单的磷腈碱 ( t -BuP ₁ ) ，邻苯二甲酸酐和环氧乙烷 (EO) 的有机催化开环交替共聚 (ROAP) 取得了重大成功。获得了具有完美交替序列分布、可控摩尔质量和低分散性 ( Đ _M < 1.1) 的聚酯。ROAP 表现出独特的活性，因此很容易实现交替聚酯的嵌段、非线性、末端功能结构和聚合后改性。溶剂、过量的 EO 和催化剂可以轻松回收和重复使用。t -BuP ₁的理想碱度被认为对 ROAP 的高选择性和纯度至关重要，它产生了一种自缓冲机制，使羧基和羟基末端具有适当的活性，以允许以严格交替的方式进行链增长并完全避免副反应（环氧化物自蔓延、酯交换) 即使在酸酐完全转化时。