Various star-shaped copolymers of methyl methacrylate (MMA) and n-butyl methacrylate (nBMA) were synthesized in one pot with RuCl2(PPh3)(3)-catalyzed living radical polymerization and subsequent polymer linking reactions with divinyl compounds. Sequential living radical polymerization of nBMA and MMA in that order and vice versa, followed by linking reactions of the living block copolymers with appropriate divinyl compounds, afforded star block copolymers consisting of AB- or BA-type block copolymer arms with controlled lengths and comonomer compositions in high yields (greater than or equal to90%). The lengths and compositions of each unit varied with the amount of each monomer feed. Star copolymers With random copolymer arms were prepared by the living radical random copolymerization of MMA and nBMA followed by linking reactions.