Synthesis of poly(vinyl acetate)-b-poly(dimethylsiloxane)-b-poly(vinyl acetate) triblock copolymers by iodine transfer polymerization

Iodine transfer polymerization of vinyl acetate in bulk, initiated by α,α′-azobisisobutyronitrile at 80 °C, has been successfully performed in the presence of an α,ω-diiodo-poly(dimethylsiloxane) macrotransfer agent. The formation of a triblock copolymer PVAc-b-PDMS-b-PVAc has been proved by 1H NMR and size exclusion chromatography analyses. The analysis of the chain-ends has been performed using 1H NMR. It was found that a large amount of inverse chain-ends is present at the end of the polymerization. Moreover, the formation of several other side products by degradation of the functional chain-ends has been evidenced.