Li Heng, Zhao Junpeng, Zhang Guangzhao
Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, People's Republic of China.
ACS Macro Lett. 2017 Oct 17;6(10):1094-1098. doi: 10.1021/acsmacrolett.7b00654. Epub 2017 Sep 20.
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 (-BuP). Polyesters with perfectly alternating sequence distribution, controlled molar masses, and low dispersities ( < 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 -BuP 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.
通过使用一种简单的磷腈碱（-BuP），邻苯二甲酸酐与环氧乙烷（EO）的有机催化开环交替共聚（ROAP）取得了重大成功。得到了具有完美交替序列分布、可控摩尔质量和低分散度（<1.1）的聚酯。ROAP表现出独特的活性，因此可以很容易地实现嵌段、非线性、端基功能化结构以及交替聚酯的后聚合改性。溶剂、过量的EO和催化剂可以轻松回收并重复使用。-BuP理想的碱度被认为对ROAP的高选择性和纯净度至关重要，这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，从而允许链以严格交替的方式增长，即使在酸酐完全转化的情况下也能完全避免副反应（环氧化物自增长、酯交换）。
