Mechanism and kinetics of RAFT (reversible addition-fragmentation chain transfer)-based controlled radical polymerization of styrene

Controlled radical polymerization (CRP) is mechanically based on a common concept of alternating activation-deactivation process. A number of activation-deactivation cycles bring about low-polydispersity polymers. The low polydispersities of the polymers yielded by reversible addition-fragmentation chain transfer (RAFT)-based CRP indicates that the magnitude of exchange rate constant k_ex or the activation rate constant k_act is exceptionally large. The mechanism of activation involves a RAFT process. The k_act of the RAFT process of styrene as a function of polymerization rate and temperature was examined to obtain not only the quantitative magnitudes of k_act and the related activation energy but also to establish the activation mechanisms of this system.