Phosphazene-Promoted Metal-Free Ring-Opening Polymerization of Ethylene Oxide Initiated by Carboxylic Acid

• Published in: Macromolecules Vol. 47; no. 5; pp. 1693 - 1698
• Main Authors: Zhao, Junpeng, Pahovnik, David, Gnanou, Yves, Hadjichristidis, Nikos
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 11.03.2014
• Subjects: Applied sciences; carboxylic acids; engineering; ethylene oxide; Exact sciences and technology; Physicochemistry of polymers; polyethylene glycol; Polymerization; Polymers and radiations; transesterification; Strong base; Ethylene oxide polymer; Ring opening polymerization; Base catalysis; Carboxylic acid; Priming activity; Living polymer; Reaction mechanism; Anionic polymerization; Phosphorus compound; Experimental study; Catalyst activity
• ISSN: 0024-9297; 1520-5835; 1520-5835
• DOI: 10.1021/ma500067j

The effectiveness of carboxylic acid as initiator for the anionic ring-opening polymerization of ethylene oxide was investigated with a strong phosphazene base (t-BuP4) used as promoter. Kinetic study showed an induction period, i.e., transformation of carboxylic acid to hydroxyl ester, followed by slow chain growth together with simultaneous and fast end-group transesterification, which led to poly(ethylene oxide) (PEO) consisting of monoester (monohydroxyl), diester, and dihydroxyl species. An appropriate t-BuP4/acid ratio was proven to be essential to achieve better control over the polymerization and low dispersity of PEO. This work provides important information and enriches the toolbox for macromolecular and biomolecular engineering with protic initiating sites.