Mechanism and Kinetics of the Persulfate-Initiated Polymerization of Acrylamide

A mechanism has been developed for the polymerization of acrylamide initiated with potassium persulfate. It has been found that donor-acceptor interactions between the monomer and initiator cause the formation of a charge-transfer complex which acts as a secondary source of initiation. This "weakly bonded complex" will be shown to be equivalently represented as a "diffuse monomer-swollen cage". That is, the complex and cage treatments are non-discriminating models of the same physical phenomena as far as amide-persulfate interactions are concerned. This analogy will enable the development of a kinetic model which can predict the observed high rate orders with respect to monomer concentration without the thermodynamic inconsistencies characteristic of previous mechanisms. The efficiencies of thermal and monomer-enhanced decomposition will also be included. The mechanism will be generalized for nonionic and ionogenic acrylic water soluble monomers in polar solvents.