Pseudoliving polymerization of vinyl acetate mediated by reversible addition-fragmentation chain-transfer agents

Abstract

The homopolymerization of vinyl acetate mediated by dithiobenzoates and trithiocarbonates as reversible addition-fragmentation chain-transfer agents is studied. The polymerization of vinyl acetate is characterized by some distinct features: (i) a substantial role of chain-termination reactions involving radical intermediates in the kinetics of the process that increases as the concentrations of the reversible additionfragmentation chain-transfer agent and the initiator increase and as temperature decreases and (ii) the occurrence of side reactions of chain transfer to monomers and polymers. The role of these reactions significantly increases with conversion of the monomer. Thus, in order to prepare a narrowly dispersed PVA via the reversible addition-fragmentation chain-transfer mechanism, the process should be conducted to small conversions (15–20%) at moderately high temperatures (80°C) and at a small molar excess of the reversible addition-fragmentation chain-transfer agent with respect to the initiator. A technique for the synthesis of block copolymers based on PVA and poly(n-butyl acrylate) via the reversible addition-fragmentation chain-transfer mechanism is developed.