Control of living free-radical polymerization by a new chiral nitroxide and implications for the polymerization mechanism

This paper reports that asymmetric nitroxide, 2,5-dimethyl-2,5-diphenylpyrrolidin-1-oxyl, mediates effectively free-radical polymerization of styrene. The polymerization is faster, gives better molecular weight control compared to TEMPO-mediated polymerization, but, unlike the latter, does not require addition of external strong acids. The amount of the nitroxide rather than benzoyl peroxide control the molecular weight. This paper also provides some mechanistic evidence that propagation indeed occurs from the fully dissociated radicals.