AbstractThe reaction mechanism of the redox initiation system persulfate/N,N,N′,N′‐tetramethyl‐ethylenediamine (TMEDA) was studied by spin trapping technique and ESR spectra. The free radical (CH3)2NCH2CH2(CH3)NCH ˙2(1)is one of the initial free radicals responsible for the initiation of the vinyl polymerization in addition to the sulfate free radical (HO3SO˙). The result of amino end group analysis confirmed the fact that the free radical1initiates vinyl polymerization and becomes the end group of the resulting polymers. The effect of TMEDA concentration on the final percentage of conversion of acrylamide polymerization and on the molecular weights of the resulting polymer were also studied. An initiation mechanism w