Synthesis of polystyrene-polyacrylate block copolymers by nitroxide-mediated radical polymerization

This paper discusses the conditions the best suited to the preparation of well-defined polystyrene (PS) / poly(n-butyl acrylate) (PBuA), using a β-hydrogen containing phosphonylated nitroxide. Using kinetic data to compute the rates of cross-addition and propagation of the second monomer, it is demonstrated that polymerizing first n-butyl acrylate (BuA) should give rise to well-defined PBuA-b-PS copolymer samples. This prediction was experimentally confirmed subsequently. When styrene was polymerized first, the copolymer formed was contaminated with a substantial amount of residual PS macroinitiator : the difference between the rates of cross-addition and propagation of BuA resulted in a fast growth of those of the PBuA blocks that were initiated, causing the medium to partition in mesophases with the residual PS precursor entrapped in the monomer-poor phase.