Kinetic study of the aqueous free-radical polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid via an online proton nuclear magnetic resonance technique

摘要

The free-radical polymerization of 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) in aqueous media and in the presence of potassium persulfate (KPS) as a thermal initiator was studied. The ~1H-NMR method was applied to record the reaction data in online gain. The effects of the monomer and initiator concentrations and also the reaction temperature were studied. The order of reaction with respect to the monomer was much greater than unity (1.94). None of the three theories describing an order of reaction higher than unity could predict the AMPS polymerization mechanism in this study. So, a new mechanism is presented. It is suggested that initiation took place through the formation of a complex between the initiator and monomer, and termination occurred not only by a bimolecular reaction but also by a monomolecular reaction. The order with respect to KPS was 0.49; this was consistent with classical kinetic theory. The determined activation energy at the overall rate of reaction was 92.7 kJ mol ~(-1) K ~(-1).