Metal-free ring-opening oligomerization of glycidyl phenyl ether (GPE) initiated with tetra-n-butylammonium fluoride (n-Bu4NF) (5.0 mol %) was performed in the presence of poly(ethylene glycol) monomethyl ether (PEGM) (5.0, 10, 20 mol %) as a chain transfer agent, by which the resulting polymers having narrow molecular weight distribution (M-w/M-n<1.2) were obtained in 80-84% yield. Solubility of the obtained polymers in water increased with the increase of amount of PEGM, owing to an increase of number of PEGM-block-oligo(GPE) molecules compared to that of oligo(GPE) molecules having FCH2- group at the initiating end as well as a decrease in degree of oligomerization of oligo(GPE). The PEGM-block-oligo(GPE) was isolated by filtration of the polymer aqueous solution, whose number-average molecular weights determined by NMR spectroscopic analysis were almost consistent to the theoretical values. The PEGM-block-oligo(GPE) formed micelles in aqueous media, whose average particle diameter was 58 and 140 nm for the copolymers having a composition of PEGM:GPE=62:38 and 53:47, respectively. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4451-4458