Multifunctional ATRP initiators: Synthesis of four-arm star homopolymers of methyl methacrylate and graft copolymers of polystyrene and poly(t-butyl methacrylate)

Tetrakis bromomethyl benzene was used as a tetrafunctional initiator in the synthesis of four-armed star polymers of methyl methacrylate via atom transfer radical polymerization (ATRP) with a CuBr/2,2 bipyridine catalytic system and benzene as a solvent. Relatively low polydispersities were achieved, and the experimental molecular weights were in agreement with the theoretical ones. A combination of 2,2,6,6-tetramethyl piperidine-N-oxyl-mediated free-radical polymerization and ATRP was used to synthesize various graft copolymers with polystyrene backbones and poly(t-butyl methacrylate) grafts. In this case, the backbone was produced with a 2,2,6,6-tetramethyl piperidine-N-oxyl-mediated stable free-radical polymerization process from the copolymerization of styrene and p-(ch4loromethyl) styrene. This polychloromethylated polymer was used as an ATRP multifunctional initiator for t-butyl methacrylate polymerization, giving the desired graft copolymers.