Preparation of onion-like multilayered particles comprising mainly poly(iso-butyl methacrylate)-block-polystyrene by two-step AGET ATRP

Synthesis of multilayered composite polymer particles comprising mainly poly(iso-butyl methacrylate)-block-polystyrene (PiBMA-b-PS) has been carried out by the use of two-step activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) in aqueous microsuspension. PiBMA-Br macroinitiator seed particles were prepared in the first step, followed by swelling with styrene and second step (seeded) polymerization. The blocking efficiency in the second step was found to be crucial with regards to the resulting particle morphology. A disordered sea-island morphology was obtained when the blocking efficiency was 47% (73% conversion), whereas a blocking efficiency of 61% (71% conversion) resulted in the formation of multilayered particles. High blocking efficiency can be achieved by careful adjustment of the activation rate by proper choice of polymerization temperature and amount of reducing agent (ascorbic acid).