Reversible chain transfer catalyzed activation processes

RTCP involves a reversible chain transfer (RT) process with a catalyst (Scheme 4a) that improves the dispersity control, as well as the mentioned small contribution of DT (Scheme Id). The catalyst can be, e.g., Af-iodosuccinimide (NIS) (Scheme 4a) [31], and works as a deactivator. Polymer (which is originally supplied by the conventional radical initiator) reacts with NIS to produce N-succinimide radical (NS ). NS works as an activator of Polymer-I to generate Polymer and NIS again. This cycle allows for frequent reversible activation of Polymer-I. This process is a reversible chain transfer of NIS that catalytically activates Polymer-I. Therefore, the polymerization was termed reversible chain transfer catalyzed polymerization (RTCP). Regarding the components used, RTCP is similar to initiators for continuous activator regeneration (ICAR)-ATRP [65]. Both systems use a monomer, a dormant species (alkyl iodide or alkyl bromide), a conventional radical initiator, and a deactivator [NIS or copper (II)] to regenerate a highly reactive activator [NS or copper (I)]. 

A subset of this process is the transition metal catalyzed, reversible cleavage of the covalent bond in the dormant species via a redox process (Scheme 2). Since the key step in controlling the polymerization is transfer of an atom (or group) between a dormant chain and a transition metal catalyst in a lower oxidation state forming an active chain end and a transition metal deactivator in a higher oxidation state, this process was named atom transfer radieal polymerization (ATRP) [27-32]. 

---