An efficient and versatile polymerization protocol [enhanced spin capturing polymerization (ESCP)] is developed based on the enhanced capturing of macroradicals with a nitrone. It is demonstrated that nitrones employed at ambient and/or relatively low temperatures can efficiently control the molecular weight of the formed polymers in aqueous solution as well as in bulk. In addition, the facile formation of ABA triblock copolymers is feasible. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] Published online 25 September 2008