Applications of metal-free living cationic polymerization of vinyl ethers using HCl center dot Et2O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of epsilon-caprolactone (CL) with HCl center dot Et2O as a ring-opening polymerization. This combination method is a metal-free polymerization using HCl center dot Et2O. The formation of poly(isobutyl vinyl ether)-b-poly(epsilon-caprolactone) (PIBVE-b-PCL) and poly(tert-butyl vinyl ether)-b-poly(epsilon-caprolactone) (PTBVE-b-PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA-b-PCL by transformation of acid hydrolysis of tert-butoxy moiety of PTBVE in PTBVE-b-PCL. The synthesized copolymers showed well-defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by H-1 NMR, size exclusion chromatography, and differential scanning calorimetry. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169-5179, 2009