Transfer to initiator and induced decomposition

Transfer to initiator can be a major complication in polymerizations initiated by diacyl peroxides. The importance of the process typically increases with monomer conversion and the consequent increase in the [initiator] [monomer] 

In BPO initiated S polymerization, transfer to initiator may be the major chain tennination mechanism, For bulk S polymerization with 0.1 M BPO at 60 C up to 75% of chains are terminated by transfer to initiator or primary radical termination ( 75% conversion). A further consequence of the high incidence of chain transfer is that high conversion PS formed with BPO initiator tends to have a much narrower molecular weight distribution than that prepared with other initiators e.g. AIBN) under similar conditions. 

Other radicals present in the reaction medium may also induce the decomposition of BPO and other diacyl peroxides. These include initiator-derived and stable radicals e.g. galvinoxyl, triphcnylmcthyl and nitroxides ). 

---