Effect of organized anionic surfactant system on kinetics of polymerization of acrylonitrile initiated by Ce(IV): Citric acid and other organic substrates

Abstract

The polymerization of acrylonitrile (AN) using the Ce(IV)-citric acid (CA) redox system as an initiator in aqueous nitric acid solution, in the presence of an anionic surfactant, sodium dodecyl sulfate (SDS), has been kinetically studied at a temperature range of 25-45°C. The rate of polymerization (R p ) and disappearance of Ce(IV) (-R Ce ) increase with increasing concentration of SDS, above its critical micelle concentration (cmc), when the surfactant molecules are organized. R p was found to be proportional to [AN] 1.5 and [CA] 0.5 . With other organic substrates, R p follows the increasing order of sorbitol ≥ mannitol > glycerol > CA. But it was found to decrease considerably in the presence of cationic surfactant (CTAB), and nonionic surfactant (Triton-X-100) had no effect on the rate. -R Ce varies linearly with [Ce(IV)] and [CA]. Both R p and -R Ce increase with increasing temperature. The overall activation energy was found to be 18.31 and 13.72 kcal/mol in the absence and presence of 0.015M SDS, respectively. The chain length of the polyacrylonitrile has also increased with increasing SDS concentration