Self-Buffering Organocatalysis Tailoring Alternating Polyester

• Published in: ACS macro letters Vol. 6; no. 10; pp. 1094 - 1098
• Main Authors: Li, Heng, Zhao, Junpeng, Zhang, Guangzhao
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.10.2017
• ISSN: 2161-1653; 2161-1653
• DOI: 10.1021/acsmacrolett.7b00654

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.