Diblock copolymers of poly(ethylene-co-butylene) and polystyrene or poly(4-acetoxystyrene) are synthesized by atom transfer radical polymerization (ATRP) using a 2-bromopropionic ester macroinitiator prepared from commercial monohydroxyl functional narrow dispersity hydrogenated polybutadiene (Kraton Liquid Polymer, L-1203). ATRP carried out in bulk and in xylene solution with cuprous bromide and two different complexing agents 2,2'-bipyridine (bipy) and 1,1,4,7,10,10-hexamethyltriethylenetetraamine (HMTETA) yielded well-defined diblock copolymers with polydispersities around 1,3. The diblock copolymer with poly(4-acetoxystyrene) was hydrolyzed to the corresponding poly(4-hydroxystyrene) sequence.