A new class of amphiphilic organometallic block copolymers with cationic organoboron pendant groups was developed. Selective replacement of one of the bromine substitutents on each boryl group of the block copolymer PSBBr2-b-PS with an organometallic reagent ArM (ArM = 2,4,6-trimethylphenyl copper, 4-t-butylphenyltrimethyl tin) followed by treatment with 2,2'-bipyridine gave the novel block copolymers [3Ar](Br)(n) as light yellow solid materials that show good stability in air and moisture and high solubility in most organic solvents. Their structure and composition were confirmed by multinuclear NMR, GPC, and elemental analysis. Highly regular micellar aggregates form in block-selective solvents (e.g., MeOH, toluene) as demonstrated by H-1 NMR, dynamic light scattering, and transmission electron microscopy. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6612-6618, 2009