▁as ▁closed - shell ▁c ob alt ▁species ). ▁Systems ▁based ▁on ▁deg ener ative ▁transfer ▁do ▁not ▁proceed ▁via ▁the ▁persistent ▁radical ▁effect ▁( PRE ). ▁Instead ▁an ▁active ▁propag ating ▁radical ▁inter changes ▁its ▁role ▁with ▁a ▁lat ent ▁radical ▁in ▁a ▁d orm ant ▁complex . ▁The ▁activation ▁of ▁one ▁polym er ▁chain ▁means ▁the ▁de activ ation ▁of ▁another ▁polym er ▁chain . ▁If ▁the ▁exchange ▁process ▁is ▁much ▁faster ▁than ▁the ▁polym er isation ▁rate ▁( k p ), ▁effectively ▁all ▁polym er ▁ch ains ▁grow ▁at ▁the ▁same ▁rate . ▁Because ▁the ▁large ▁polym er ▁ch ains ▁diff use ▁much ▁slower ▁than ▁the ▁small ▁organ ic ▁radical s , ▁and ▁thereby ▁terminate ▁much ▁slower ▁via ▁ 2 nd ▁order ▁radical - rad ical ▁coupling ▁or ▁dis pro port ion ation , ▁long ▁ch ains ▁effectively ▁build - up ▁at ▁c ob alt ▁while ▁the ▁small ▁radical s ▁keep ▁termin ating . ▁This ▁leads ▁to ▁a ▁des irable ▁narrow ▁mole cular ▁weight ▁distribution ▁of ▁the ▁polym er ▁at ▁high ▁polym er ization ▁rates . ▁D T - C MR P ▁is ▁an ▁associ ative ▁process , ▁which ▁for ▁Co III ( por )( alk yl ) ▁species ▁implies ▁formation ▁of ▁a ▁ 6 - coordinate ▁intermediate ▁or ▁transition ▁state . ▁Such ▁Co ( por )( alk yl ) 2 ▁species ▁formally ▁have ▁a ▁Co ( + IV ) ▁ox id ation ▁state , ▁but ▁in ▁reality ▁their ▁( elect ron ic ) ▁structure ▁is ▁best ▁described ▁as ▁a