Polystyrene-block-poly(methyl methacrylate): Initiation issues with block copolymer formation using ARGET ATRP

The synthesis, kinetics, and characterization of polystyrene and poly(methyl methacrylate) block copolymers produced by ARGET ATRP are discussed. Halogen exchange is used and the polymerization appears to be living in the generation of the second block. On further investigation, the GPC traces exhibit a shoulder, which suggests poor initiation of the macroinitiator. Previous reports suggest that to increase the initiation efficiency of the second block, 10% styrene monomer should be added to the mixture. Upon adding the 10% styrene for the second block ARGET ATRP polymerization, the appearance of a well-initiated polymer is observed. However, at greater conversions the results clearly demonstrate the production of a homopolymer/block copolymer mixture. A comprehensive exploration of ARGET ATRP for use in the formation of block copolymers is described. With polystyrene as the first block, the more reactive monomer methyl methacrylate is used to generate a second block using the halogen exchange technique and 10% comonomer. Issues with initiation efficiency and additional effects in the comonomer technique are discovered.