Polymerization of acrylamide in aqueous medium initiated with a redox system composed of cysteine and potassium bromate

Abstract

Abstract Aqueous polymerization of acrylamide initiated with a redox initiator system composed by cysteine and potassium bromate was investigated as a model of the redox initiator system composed of poly(vinyl alcohol) having a thiol groups at one end and potassium bromate. The rate of polymerization was proportional to almost the square root of cysteine and potassium bromate concentration, indicating the initiation system is a usual free radical polymerization initiator. On the other hand, the rate was proportional to the 1.8th power of the monomer concentration. The activation energy of the rate of polymerization was about 5 kcal · mol −1 , indicating also a typical redox initiation system. Chain transfer constant of polyacrylamide radical to cysteine was calculated to be 0.4. From these results, it is concluded that cysteine exerts two important roles: (1) as a reductant of the redox initiation and (2) as a powerful chain transfer reagent.