A new methodology is successfully used for the concurrent synthesis of three different copolymers, diblock, triblock, and three-armed star-block copolymers of styrene and isoprene via the living anionic polymerization with control over the molecular weight and weight fractions of each block The room temperature polymerization process has resulted in the well defined linear and radial block copolymers, when the living di-block of poly(styrene-b-isoprene) was coupled using cheap and readily available malonyl chloride as a novel coupling agent giving nearly 100% yield The resulting block copolymers have narrow polydispersity index (PDI = 1 01-1 09) with a good agreement between the calculated and the observed molecular weights The results are further supported by fractionation of the block copolymers by reversed-phase temperature gradient interaction chromatography (RP-TGIC) technique followed by size exclusion chromatography (SEC). (C) 2010 Wiley Periodicals, Inc J Polym Sci Part A Polym Chem 48: 2636-2641, 2010