Synthesis of Biocompatible and Biodegradable Block Copolymers of Polyvinyl Alcohol-block-Poly(ε-caprolactone) Using Metal-Free Living Cationic Polymerization

Applications of metal-free living cationic polymerization of vinyl ethers using HCl·Et 2 O 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 e-caprolactone (CL) with HCl·Et 2 O as a ring-opening polymerization. This combination method is a metal-free polymerization using HCl·Et 2 O. The formation of poly(isobutyl vinyl ether)-b-poly(e-caprolactone) (PIBVE-b-PCL) and poly(tert-butyl vinyl ether)-b-poly(e-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 1 H NMR, size exclusion chromatography, and differential scanning calorimetry.