Glaser coupling reaction of alkynyl groups was used as a new ring closure technique to synthesize monocyclic poly(ethylene oxide) (PEO) and polystyrene (PS) successfully The linear PEO with hydroxyl groups at both ends was prepared by ring-opening polymerization (ROP) of ethylene oxide (EO) using 2,2 dimethyl 1,3 propanediol and diphenylmethylpotassium (DPMK) as co initiators, terminated by anhydrous methanol The linear PS with hydroxyl groups at both ends was prepared by anionic polymerization using lithium naphthalenide as initiator and terminated by EO The propargyl telechelic precursors (l-PEO and l-PS) were then obtained by the reaction between hydroxyl-telechelic polymers (HO PEO OH and HO-PS OH) and propargyl bromide in the presence of sodium hydride The intramolecular cyclizations of the latter were carried out in the presence of Cu(I)Br/N N N' N '' N ''-pentamethyldiethylenetriamine (PM DETA) under mild conditions with oxygen in the air as oxidant and the efficiency was as high as nearly 100% The cyclic PEO and PS (c-PEO and c PS) were characterized by GPC, H-1 NMR, FTIR, and MALDI-TOF MS G factors (ratio of the apparent peak molar masses of cyclic product to their linear precursor) derived from GPC profiles were in the range 0 63-0 80 The highly efficient Glaser coupling took place at ambient temperature and did not need oxygen removal procedures, so It was a convenient approach for nearly quantitative preparation of cyclic polymers