RAFT-mediated polymerization- A story of incompatible data?

The mechanistic interpretation of kinetic anomalies in reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization is critically reviewed. The main conclusion of this exercise is that available data do not allow model discrimination between the two prevailing mechanistic schemes, i.e., the slow fragmentation model and the intermediate radical termination model. However, assessment of the rate parameters reveals that the incompatibilities may not be as large as previously reported in literature. Dedicated kinetic studies on model compounds should be performed to shed further light on the seemingly incompatible data that currently exists in literature. The anecdotal six orders of magnitude difference in the RAFT equilibrium constant between the slow fragmentation model and the intermediate radical termination model are reviewed. Although a clear answer for the discrepancy is still lacking, directions are found to reconcile the dispute. Reevaluation of rate constants and new insights in their chain length dependence are important in this respect. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.