Polymer formations by radical polymerization of vinyl monomer (M) initiated by an initiator (R-R') are expressed by Eq. (I), if no chain transfer reaction occurs and the termination proceeds via a recombination of the growing radicals.Therefore, radical polymerization may simply be considered as a successive insertion reaction of the monomer molecules into the R-R' bond of the initiator leading to a polymer with two initiator fragments bonded at its both ends. The radical polymerization of styrene initiated by 2,2 '-azoisobutyronitrile is only an example close to such a case'). The above assumptions are, however, generally not realized, and thus the number of initiator fragments per polymer molecule is always less than 2.If the initiator used has a high reactivity for a chain transfer to the initiator, or a part of the radical produced by the initiator easily undergoes primary radical termination, a polymer with two initiator fragments, similar to Eq. (l), can be obtained [Eq. (211. R-R'+nM +
R+M+R'(2) Therefore, the choice of such initiators in vinyl polymerization opens the possibility of synthesizing easily monofuntional or a,o-bifunctional oligomers and polymers via radical mechanism, and thus designing a polymer structure by radical polymerization.Thus, we may call such initiators initiator-tranuer agent (inifer), and/or initiatorterminator (initer). Since it is difficult to distinguish between "inifer" and "initer" for usual radical initiators, however, we propose to call them initiator-tranuer agentterminator (iniferter). The concept of "inifer" in cationic polymerization has already been proposed by Kennedy2).When iniferters such as phenylazotriphenylmethane, phenylphenylazosulfide, 1,3diphenyltriazene, alkyl perbenzoates, monosulfides etc., are used in radical polymerization, monofunctional polymers are produced, as shown in Eq.(3), as an example.
