Initiators, iniferters, initers

In each of the sections below, we will consider the initiation process separately. For each system, various initiation methods have been applied. In some cases the initiator is a low molecular weight analog of the propagating species, in other cases it is a method of generating such a species. The initiators first used in this form of living radical polymerization were called iniferters (/n/tiator - trans/er agent - chain terminator) or initers (m/tiator - chain terminator). 

These tenns were coined by Otsu and Yoshida based on the similar terminology introduced by Kennedy to cover analogous cationic systems. Except for the case of the dithiuram disulfides and related species (Section 9.3.2.1), these expressions have now fallen from favor and are no longer used as a generic terminology. In this chapter, we use the term initiator to denote alkoxyamines in NIMP and halo-compounds in ATRP despite the confusion this can create, especially when the process also involves added conventional initiators. 

In order for the characteristics of living polymerizalion to be displayed, initiators should possess the following attributes  

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Otsu used the term initers (from mftiator-terminator) for compounds such as 5 or, because some of them were also able to undergo chain transfer to initiator, iniferters (from inftiator-transyer agent-terminator). Nevertheless, the essential features of a true living polymerization such as accurately controlled molecular weights and low polydispersities were absent with 5 (and other iniferters too) since the trityl radical 7 can also to some extent initiate polymerization. 

Focusing on telechelic polymers, the concept of iniferter is probably more interesting. like initer, iniferter compounds will be able to initiate and terminate the polymerization. They also function as a CTA [84], To get telechelic polymers by radical polymerization, it is necessary to use compounds with high transfer constants along with the radical initiator. Cho and Kim [85] suggested such a system, based on the use of two compounds bear-... 

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