Effects of surfactants on acrylonitrile polymerization initiated by a Cr(VI)–cyclohexanone redox system: A kinetic study

Abstract

AbstractThe polymerization of acrylonitrile (AN) was kinetically studied with a Cr(VI)–cyclohexanone (CH) redox system as an initiator from 25 to 45° C in the presence of a surfactant. The rate of polymerization and the percentage of the monomer conversion increased as the concentration of the anionic surfactant [sodium dodecyl sulfate (SDS)] increased above its critical micelle concentration. However, the cationic surfactant (cetyltrimethylammonium bromide) reduced the rate considerably at higher concentrations, whereas the nonionic surfactant (TX‐100) had no effect on the rate. The effects of the Cr(VI), CH, AN, and H+ concentrations and the ionic strength on the rates were also examined. The presence of 0.015M SDS reduced the overall activation energy of the polymerization by 5.55 kcal/mol with respect to that in the absence of the surfactant. With increasing SDS concentration, the viscosity‐average molecular weight also increased. A suitable mechanistic scheme was proposed for the polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1147–1153, 2004