Synthesis of an asymmetric tadpole-shaped aliphatic copolyester consisting of a poly(F-caprolactone) ring and two poly(L-lactide) tails was reported for the first time. First, a high molecular weight cyclic PCL macroinitiator (M-n = 3 1,000) was prepared by intramolecular photocross-linking of "living" chains. Polymerization Of L-lactide was resumed by the tin dialkoxide containing macrocycles, thus making the targeted tadpole-shaped copolyester available. A preliminary investigation of the crystallization of these copolyesters was carried out by differential scanning calorimetry and polarized optical microscopy. (c) 2006 Elsevier Ltd. All rights reserved.