The preparation of poly(2,6-dimethyl-1,4-phenylene ether)-b-poly(ethylene terephthalate) block copolymer was performed by the reaction of the 2-hydroxyethyl modified poly(2,6-dimethyl-1,4-phenylene ether) (PPE-EtOH) with poly(ethylene terephthalate) (PET) by an in situ process, during the synthesis of the polyester. The yield of the reaction of the 2-hydroxyethyl functionalized. PPE-EtOH with PET was close to 100%. A significant proportion of the PET-b-PPE-EtOH block copolymer was found to have short PET block. Nevertheless, the copolymer structured in the shape of micelles (20 nm diameter) and very small domains with 50-200 nm. diameter, whereas unmodified PPE formed much larger domains (1.5 mu m) containing copolymer. (c) 2008 Wiley Periodicals, Inc.