▁Re vers ibile ▁term ination ▁( RT ), ▁leading ▁to ▁the ▁persistent ▁radical ▁effect ▁( PRE ) ▁D eg ener ative ▁transfer ▁( DT ). ▁ ▁Historical ▁background ▁Cob alt ▁medi ated ▁control ▁of ▁R P ▁re actions ▁through ▁C CT ▁was ▁discovered ▁by ▁Sm ir nov ▁and ▁Mar chen ko ▁in ▁ 1 9 7 5 . ▁C MR P ▁through ▁revers ible ▁term ination ▁( pers istent ▁radical ▁effect ) ▁was ▁introduced ▁in ▁ 1 9 9 4 . ▁ ▁More ▁recent ▁develop ments ▁focus ▁on ▁C MR P ▁via ▁deg ener ative ▁transfer ▁( DT ) ▁mechan isms , ▁and ▁combinations ▁of ▁R T ▁and ▁D T ▁mechan isms . ▁ ▁Control ▁via ▁revers ible ▁term ination ▁( pers istent ▁radical ▁effect ) ▁ ▁In ▁many ▁cases , ▁C MR P ▁explo its ▁the ▁weak ▁c ob alt ( III )- car bon ▁bond ▁to ▁control ▁the ▁radical ▁polym er ization ▁reaction . ▁The ▁Co - C ▁bond ▁containing ▁radical ▁initi ator ▁easily ▁breaks ▁up ▁( by ▁heat ▁or ▁by ▁light ) ▁in ▁a ▁carbon ▁free ▁radical ▁and ▁a ▁c ob alt ( II ) ▁radical ▁species . ▁The ▁carbon ▁radical ▁starts ▁the ▁growth ▁of ▁a ▁polym er ▁chain ▁from ▁the ▁CH 2 = CH X ▁mon omer ▁as ▁in ▁a ▁free ▁radical ▁polym er ization ▁reaction . ▁Cob alt ▁is ▁unusual ▁in ▁that ▁it ▁can ▁revers ibly ▁reform ▁a ▁c oval ent ▁bond ▁with ▁the ▁carbon ▁radical ▁termin us ▁of ▁the ▁growing ▁chain . ▁This ▁reduces ▁the ▁concentration ▁of