Synthesis of (vinyl acetate)-terminated polystyrene macromonomers by free-radical polymerization in the presence of vinyl iodoacetate

(Vinyl acetate)-terminated polystyrene macromonomers (VAc-PSt-I) were synthesized by free-radical polymerization of styrene in the presence of vinyl iodoacetate (VAcI) as a chain transfer agent. Macromonomers with functionality close to unity were obtained, which were characterized by H-1-NMR and size exclusion chromatography (SEC). No branching or incorporation of VAcI was noticed. The chain transfer constant of VAcI was determined by an integral method (C-tr = 0.46). Attempts to copolymerize the VAc-PSt-I macromonomer with vinyl acetate (VAc) failed due to the involvement of the iodine end groups in chain transfer processes, which led to the fast formation of polystyryl radicals with a very low reactivity for VAc. The replacement of the iodine atoms by azido groups allowed for the copolymerization to be carried out successfully. The formation of the graft copolymer was proved by SEC and H-1-NMR measurements. It was found that the reactivity of the macromonomer is practically equal to that of VAc monomer (1/r(VAc) = 1.07). (C) 2001 Elsevier Science Ltd. All rights reserved,