New chemistry for controlling the dynamics and yields of radical-mediated polyolefin modifications is adapted to prepare impact-resistant thermoplastic vulcanizates. Dynamic vulcanization of polypropylene (PP) + poly(ethylene-co-octene) (EOC) blends using small amounts of acryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl (AOTEMPO) overcomes the limitations of conventional peroxide formulations, giving products with fine EOC particle dispersions, high PP matrix viscosities, and superior mechanical toughness. Guidelines for selecting starting materials and reagent concentrations are developed before assessing the merits of an AOTEMPO-derived products relative to benchmark blend materials. Measurements of dispersed-phase size distributions and melt-state oscillatory shear rheological properties are combined with solid-state impact resistance, flexural, and tensile data to identify the strengths and limitations of AOTEMPO chemistry with respect to impact-toughening applications. POLYM. ENG. SCI., 58:1999-2007, 2018. (c) 2017 Society of Plastics Engineers