ИСТИНА

Controlled synthesis of amphiphilic copolymers with desired monomer unit sequence and targeted molecular masses is an urgent task of polymer chemistry. To solve this problem the reversible addition-fragmentation chain transfer polymerization (RAFT) was applied. The regularities of the copolymerization of styrene and acrylic acid in bulk and the solvents of different polarity (N,N-dimethylformamide, DMF and 1,4-dioxine, DO) initiated by AIBN and mediated by bifunctional RAFT agents, namely dibenzyl trithiocarbonate (BTC), polyacrylic acide (PAATC) and polystyrene (PSTC) containing trithiocarbonate group within the chain were examined. All the investigated systems exhibit the features of controlled radical polymerization. The copolymers formed are characterized by narrow MWD; their MW increase with progress of monomer conversion independently from the solvent and molar ratio of the monomers. The relative reactivity ratios of the monomer are found to depend not only from the solvent nature, but also from the nature of the RAFT agent (Table). The increase of the hydrophilicity of RAFT agent (PAATC) results in increase of styrene activity in copolymerization, while the increase of hydrophobicity of RAFT agent (PSTC) results in decrease of the difference in the monomer activity. In combination with the living nature of the process it results in the formation of the narrow dispersed copolymers with different microstructure from the same monomer feed. Table. Relative monomer reactivity ratios in styrene/acrylic acid copolymerization RAFT agent Nonlinear least-squares method BTC rAA =0.08  0.01 rS =0.850.03 PAATC (Mn = 8900) rAA =0.080.04 rS =3.031.78 PSTC (Mn = 4100) rAA =0.11  0.01 rS =0.540.03