Control over the relative reactivities of monomers in RAFT copolymerization of styrene and acrylic acid.

The relative monomer reactivities in the reversible addition-fragmentation chain transfer (RAFT) radical copolymerization of styrene (S) and acrylic acid (AA) in a solution of the polar solvent N , N -dimethylformamide are found to be dependent on the chemical nature of the RAFT agent. Polymeric RAFT agents based on polyacrylic acid enhance the difference in monomer reactivities (dithiobenzoate - r AA = 0.09 ± 0.02, r S = 3.5 ± 1.2, trithiocarbonate - r AA = 0.08 ± 0.04, r S = 3.03 ± 1.78) compared to low molecular weight RAFT agents (dibenzyl dithiobenzoate - r AA = 0.14 ± 0.01, r S = 1.00 ± 0.01, dibenzyl trithiocarbonate - r AA = 0.08 ± 0.01, r S = 0.85 ± 0.03). The opposite effect on the relative reactivity of acrylic acid is observed when polymeric RAFT agents based on polystyrene are used (dithiobenzoate - r AA = 3.3 ± 0.4, r S = 0.72 ± 0.05, trithiocarbonate - r AA = 0.11 ± 0.01, r S = 0.54 ± 0.03). In all the investigated systems the copolymers formed are characterized by narrow MWD due to the high efficiency of the chosen RAFT agents.