Acrylamide polymerization initiated with the redox system Ce(IV)-cyclohexanone in micellar phase: A kinetic study

Abstract

The effect of an organized anionic surfactant, i.e. sodium dodecyl sulfate (SDS), on the acrylamide (AM) polymerization initiated with the redox system Ce(IV)-cyclohexanone (CH) in aqueous nitric acid was kinetically studied over a temperature range of 25 -45 °C. With increasingconcentration of SDS, above its critical micelle concentration (CMC) the rate of polymerization, R p(obs) , as well as the rate of Ce(IV) consumption, -R Ce(obs) , were found to increase, while in the presence of cetyltrimethylammonium bromide (CTAB ) these rates decreased considerably. R p(obs) is proportional to [Ce(IV)] 0.5 , [CH] 0.5 and [AM] 1.5 ,-R Ce(obs) also increases with increasing concentration of Ce(IV), cyclohexanone and acrylamide. The overall activation energy for the process, in the presence and absence of 15 x 10 -3 M of SDS, was calculated to be 15.1 and 21.4 kcal/mol, respectively. The viscosity average molecular weight of polyacrylamide was found to increase with increasing SDS concentration. A suitable mechanistic scheme for the polymerization process is proposed.