Atom transfer radical polymerization (ATRP) was applied to the synthesis of AB-type brush-block-brush amphiphilic copolymers. The procedure included the following steps: (1) ATRP of methacryloyl-terminated poly(ethylene glycol methylether) macromonomer (PEG-MC) gave well-defined PEG brush macroinitiator, (2) subsequent ATRP of 2-hydroxyethyl methacrylate (HEMA) with this brush macroinitiator provided PEG brush-block-PHEMA (brush-block-coil) diblock copolymers, (3) esterification of the pendant hydroxy groups of PHEMA block with 2-bromoisobutyryl bromide yielded a block-type polyinitiator, brush-block-poly(2-(2-bromoisobutyryloxy)ethyl methacrylate) (PBIEM), (4) ATRP of HEMA using brush-block-PBIEM as polyinitiator provided AB-type brush-block-brush amphiphilic copolymers. Dilute-solution properties of such AB-type copolymer brushes were investigated by static and dynamic light scatterings. As a result, this copolymer exhibited a slightly ellipsoidal shape, i.e., Janus-type structure, in solution. (C) 2004 Elsevier Inc. All rights reserved.