The synthesis and characterization of a novel three arm star-block comprising a cumyl core out of which radiate three poly(isobutylene-b-acrylonitrile) arms is presented. The synthesis strategy comprised three major steps (see Scheme 1): 1. The synthesis of empty set(PIB-OH)(3), 2. Quantitative transformation of the -OH termini to -OCOC(CH3)(2)Br termini, and 3. Controlled ATRP of acrylonitrile mediated by the latter termini. The definition of a suitable solvent system, methylene chloride/cyclohexanone (CH2Cl2/CHO) was critical for the synthesis. The empty set(PIB-b-PAN)3; M-n,M-PIB (block) = 6000 g/mol and M-n,M-PAN block = 1,800 g/mol was characterized by solid sate C-13 NMR spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis.