The amphiphilic cyclic poly(ethylene oxide)-block-polystyrene [c-(PEO-b-PS)] was synthesized by cyclization of propargyl-telechelic poly(ethylene oxide)-block-polystyrene-block-poly(ethylene oxide) (-PEO-b-PS-b-PEO-) via the Glaser coupling. The hydroxyl-telechelic ABA triblock PEO-b-PS-b-PEO was first prepared by successive living anionic polymerization of styrene and ring-opening polymerization of ethylene oxide, and then the hydroxyl ends were reacted with propargyl bromide to obtain linear precursors with propargyl terminals. Finally, the intramolecular cyclization was conducted in pyridine under high dilution by Glaser coupling of propargyl ends in the presence of CuBr under ambient temperature, and the c-(PEO-b-PS) was directly obtained by precipitation in petroleum ether with high efficiency. The cyclic products and their corresponding linear precursor -PEO-b-PS-b-PEO- were characterized by means of GPC, (1)H NMR, and FTIR. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4766-4770, 2011