Well-defined macromonomers of poly(ethylene oxide) and poly(tert-butyl methacrylate) were obtained by anionic polymerization induced directly by the carbanion issued from 2-methyl-2-oxazoline. When ethylene oxide was added to this carbanion with lithium as the counterion, a new compound able to initiate the polymerization of ε-caprolactone in an anionically coordinated way was synthesized, and this led to well-defined poly(ε-caprolactone) macromonomers. © 2005 Wiley Periodicals, Inc