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

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 increasing concentration 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 × 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.