A monomode microwave reactor was used for the synthesis of designed star-shaped polymers, which were based on dipentaerythritol with six crystallizable arms of poly(epsilon-caprolactone)-b-poly(L-lactide) (PCL-b-PLLA) copolymer via a two-step ring-opening polymerization (ROP). The effects of irradiation conditions on the molecular weight were studied. Microwave heating accelerated the ROP of CL and LLA, compared with the conventional heating method. The resultant hexa-armed polymers were fully characterized by means of FTIR, H-1 NMR spectrum, and GPC. The investigation of thermal properties and crystalline behaviors indicated that the crystalline behaviors of polymers were largely depended on the macromolecular architecture and the length of the block chains. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5063-5071, 2010