ICAR: initiators for continuous activator regeneration

Figure 2.3 ATRP current status and future perspectives. ARGET activator regenerated by electron transfer, eATRP electron-atom transfer radical polymerisation, ICAR initiators for continuous activator regeneration and SARA supplemental activator and reducing agent. Reproduced with permission from K.Matyjaszewski, Macromolecules, 2012,45,10,4015.

Cu(l)X is needed for activation, these methods utilize chemical additives [101] or electrochemical equipment (i.e., electrodes) [102] to recycle generated CullllX back to Cu(l) X. One example for a novel method is initiators for continuous activator regeneration (ICAR) which uses a radical sources [e.g., azobisisobutyronitrile (AIBN)] to convert the in situ formed Cu(ll)X2 back to Cu(l)X [101]. As a result, ICAR ATRP only requires 10-50ppm catalyst. 

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)]. 

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