▁radical s ▁to ▁a ▁minimum ▁and ▁thereby ▁minim izes ▁und es irable ▁term ination ▁re actions ▁by ▁recom bin ation ▁of ▁two ▁carbon ▁radical s . ▁The ▁c ob alt ▁tra pping ▁re agent ▁is ▁called ▁a ▁persistent ▁radical ▁and ▁the ▁c ob alt - c apped ▁polym er ▁chain ▁is ▁said ▁to ▁be ▁d orm ant . ▁This ▁mechanism ▁is ▁called ▁revers ible ▁term ination ▁and ▁is ▁said ▁to ▁operate ▁via ▁the ▁" pers istent ▁radical ▁effect ". ▁When ▁the ▁mon omer ▁la cks ▁pro tons ▁that ▁can ▁be ▁easily ▁abstract ed ▁by ▁the ▁c ob alt ▁radical , ▁( catal yt ic ) ▁chain ▁transfer ▁is ▁also ▁limited ▁and ▁the ▁R P ▁reaction ▁becomes ▁close ▁to ▁‘ l iving ’ . ▁ ▁Control ▁via ▁catal yt ic ▁chain ▁transfer ▁ ▁Catal yt ic ▁chain ▁transfer ▁is ▁a ▁way ▁to ▁make ▁shorter ▁polym er ▁ch ains ▁in ▁a ▁radical ▁polym er ization ▁process . ▁The ▁method ▁involves ▁adding ▁a ▁catal yt ic ▁chain ▁transfer ▁agent ▁to ▁the ▁reaction ▁mixture ▁of ▁the ▁mon omer ▁and ▁the ▁radical ▁initi ator . ▁Catal yt ic ▁chain ▁transfer ▁proceed s ▁via ▁hydro gen ▁atom ▁transfer ▁from ▁the ▁organ ic ▁growing ▁polym ery l ▁radical ▁to ▁c ob alt ( II ), ▁producing ▁a ▁polym er ▁vin yl - end ▁group ▁and ▁a ▁c ob alt - h yd ride ▁species ▁( equ ilib rium ▁ 2 ). ▁The ▁Co - H ▁species ▁then ▁react s ▁with ▁the ▁mon omer ▁to ▁start ▁a ▁new ▁Co ( III