Cyclic oligo(potassiurn glycidoxide) activated 18-crown-6 is applied as a macroinitiator for the polymerization of propylene oxide, 1-butylene oxide and styrene oxide. This polymerization results in new star-shaped polyethers with a cyclic core, The size of the core and the number of its arms depends on the concentration of crown ether used for preparation of the macroinitiator. (c) 2007 Elsevier Ltd. All rights reserved.