Thermoplastic elastomers based on well-defined 10- and 20 arm star-like block copolymers containing middle soft poly(n-butyl acrylate) (PBA) block and outer hard poly(alpha-methylene-gamma-butyrolactone) (PMBL) block were synthesized by atom transfer radical polymerization (ATRP). Phase separated cylindrical or lamellar morphologies, depending on the copolymers composition and the annealing temperature of the films, were observed by atomic force microcopy and small-angle X-ray scattering. The mechanical and thermal properties of the copolymers were thoroughly characterized. The prepared copolymers retained their phase separated morphology even at temperatures exceeding 300 degrees C. Both tensile strength and elongation values for the star-like copolymers were considerably higher than for linear copolymers with similar composition. (C) 2010 Elsevier Ltd. All rights reserved.