Polymerization of acrylamide in aqueous medium initiated with a redox system of cysteine and ammonium persulfate

Aqueous polymerization of acrylamide initiated with a redox system of cysteine containing a thiol group and ammonium persulfate was investigated. This is a model of the redox initiator system composed of poly(vinyl alcohol) having a thiol group at one end and ammonium persulfate which polymerized many monomers yielding various block copolymers. The rate of polymerization was proportional to the 0.5 power of the concentrations of cysteine and of ammonium persulfate and 1.0 power of monomer concentration, indicating the initiator system to be a usual free radical polymerization initiator. The activation energy of over-all rate of polymerization was 4 kcal mol(-1) indicating a typical redox initiator of the system. Rate constant of the redox decomposition reaction, k, was determined as 1.7 L mol(-1) s(-1). Chain transfer constant of polyacrylamide radical to ammonium persulfate was calculated to be 0.65.