The Synthesis of brush copolymers based oil a strictly 1,4-polybutadiene (PB) backbone is reported via the "grafting from" strategy by combining two highly controlled polymerization methods: ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). ROMP of a cis-3,4-disubstituted cyclobutene derivative (inimer) containing two initiating sites for ATRP was First investigated with Grubb's first-generation catalyst ((Cy3P)(2)RuCl2(CHPh)), leading to well-controlled,sLpolymerization for (DPn) over bar up to 75. The well-defined 1,4-polybutadiene backbones obtained ((Mn,SEC) over bar ranging from 3600 to 25 200 g.mol(-1), PDI <= 1.16) were then used as macroinitiators in ATRP with styrene, methyl methacrylate, and tert-butyl acrylate. While styrene polymerization led to nonnegligible side reactions, well-defined PB-g-poly(methyl methacrylate) ((Mn,SEC) over bar = 19 900-98 200 g mol(-1), PDI <= 1.20) and PB-g-poly(tert-butyl acylate) butyl acrylate) ((Mn,SEC) over bar = 36 600-140 000 g mol(-1).PDI <= 1.21) were obtained through this synthetic approach. In addition, the morphology of a PB-g-poly(tert-butyl acrylate) was studied through AFM measurements. measurements.