The recently introduced procedure of quantitatively switching thiocarbonyl thio capped (RAFT) polymers into hydroxyl terminated species was employed to generate narrow polydispersity (PDI approximate to 1.2) sulfur-free poly(styrene)-block-poly(epsilon-caprolactone) polymers (26,000 <= M-n/g.mol(-1) < 45,000). The ring-opening polymerization (ROP) of L.-caprolactone (epsilon-CL) was conducted under organocatalysis employing 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). The obtained block copolymers were thoroughly analyzed via size exclusion chromatography (SEC), NMR, as well as liquid adsorption chromatography under critical conditions coupled to SEC (LACCC-SEC) to evidence the block copolymer structure and the efficiency of the synthetic process. The current contribution demonstrates that the RAFT process can serve as a methodology for the generation of sulfur-free block copolymers via an efficient end group switch. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1-10, 2011