INFLUENCE OF MONOMER COMPOSITION ON THE CHAIN TRANSFER COEFFICIENT IN METHYL METHACRYLATE/BUTYL ACRYLATE RAFT COPOLYMERIZATION

The bulk copolymerization of butyl acrylate (BA) and methyl methacrylate (MMA) in the presence of the RAFT agent with Z=—CH_2C_6H_5 and 2,2′-Azobis(isobutyronitrile)(AIBN) as an initiator was carried out at 60℃.The chain transfer coefficients (C_ tr ) at different monomer compositions were determined by the GPC peak resolution method.In the BA homopolymerization,C_ tr was up to 116 while it was about 0.1 in the MMA homopolymerization.Since C_ tr was too low,the homopolymerization of MMA mediated by the RAFT agent was out of control.In the copolymerization systems,C_ tr showed a nonlinear decrease with the increasing of MMA compositions.When a small fraction of BA was added to an MMA polymerization system,the polymerization became well controlled with PDI around 1.2 at the end of the polymerization.The changing trend of C_ tr with monomer compositions well explained the profiles of the molecular weight and its distribution against conversion with different monomer compositions.