epsilon-Caprolactone (CL) was enzymatically polymerized with 2-mercaptoethanol as the initiator, both in an oil bath and under microwave (MW) irradiation. The polymerization performed under MW irradiation maintaining equal conditions led to higher yields and less formation of side products, i.e., a higher chemoselectivity was observed. The resulting polyester with a terminal -SH moiety had a (M) over bar (n) of 3 600 g.mol(-1), determined by size exclusion chromatography (SEC), and was used as a chain transfer reagent. Subsequent copolymerization with styrene in different ratios led to polycaprolactone-block-polystyrene. SEC analysis and polarization microscopy of crystallized samples with different styrene contents proved the block copolymers.