Using core-first strategy, the amphiphilic A(4)B(4) star-shaped copolymers [poly(ethylene oxide)](4)[poly(epsilon-caprolactone)](4) [(PEO)(4)(PCL)(4)], [poly(ethylene oxide)](4)[poly(styrene)](4) [(PEO)(4)(PS)(4)], and [poly(ethylene oxide)](4)[poly(tert-butyl acrylate)](4) [(PEO)(4)(PtBA)(4)] were synthesized by mechanisms transformation combining with thiol-ene reaction. First, using a designed multifunctional mikto-initiator with four active hydroxyl groups and four allyl groups, the four-armed star-shaped polymers (PEO-Ph)(4)/(OH)(4) with four active hydroxyl groups at core position were obtained by sequential ring-opening polymerization (ROP) of ethylene oxide monomers, capping reaction of living oxyanion with benzyl chloride, and transformation of allyl groups into hydroxyl groups by thiol-ene reaction. Then, the A(4)B(4) star-shaped copolymers (PEO)(4)(PS)(4) or (PEO)(4)(PtBA)(4) were obtained by atom transfer radical polymerization (ATRP) of styrene or tert-butyl acrylate (tBA) monomers from macroinitiator of (PEO-Ph)(4)/(Br)(4), which was obtained by esterification of (PEO-Ph)(4)/(OH)(4) with 2-bromoisobutyryl bromide. The A(4)B(4) star-shaped copolymers (PEO)(4)(PCL)(4) were also obtained by ROP of epsilon-caprolactopne monomers from macroinitiator of (PEO-Ph)(4)/(OH)(4). The target copolymers and intermediates were characterized by size-exclusion chromatography, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and nuclear magnetic resonance in detail. This synthetic route might be a versatile one to various A(n)B(n) (n3) star-shaped copolymers with defined structure and compositions. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4572-4583