Three alternative routes, using the heterobifunctional macroinitiator technique, have been developed to obtain polystyrene-poly(tert-butyl methacrylate)-poly(ethylene oxide) triarm star block copolymers. Only the route showing the reverse initiation of tert-butyl methacrylate on potassium alkoxide leads to the pure star, whereas the other strategies lead to incomplete initiation because of either an increase in the side reactions, such as transesterification, or a decrease in the accessibility toward bulky catalysts. These limits are linked to the particular location of the initiating group at the junction of the two blocks of the copolymer precursor. (C) 2004 Wiley Periodicals, Inc.