Urea Anions: Simple, Fast, and Selective Catalysts for Ring-Opening Polymerizations

• Published in: Journal of the American Chemical Society Vol. 139; no. 4; pp. 1645 - 1652
• Main Authors: Lin, Binhong, Waymouth, Robert M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.02.2017
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.6b11864

Aliphatic polyesters and polycarbonates are a class of biorenewable, biocompatible, and biodegradable materials. One of the most powerful methods for accessing these materials is the ring-opening polymerization (ROP) of cyclic monomers. Here we report that the deprotonation of ureas generates a class of versatile catalysts that are simultaneously fast and selective for the living ring-opening polymerization of several common monomers, including lactide, δ-valerolactone, ε-caprolactone, a cyclic carbonate, and a cyclic phosphoester. Spanning several orders of magnitude, the reactivities of several diaryl urea anions correlated to the electron-withdrawing substituents on the aryl rings. With the appropriate urea anions, the polymerizations reached high conversions (∼90%) at room temperature within seconds (1–12 s), yielding polymers with narrow molecular weight distributions (Đ = 1.06 to 1.14). These versatile catalysts are simple to prepare, easy to use, and exhibit a range of activities that can be tuned for the optimal performance of a broad range of monomers.