Termination of ceric ion initiated vinyl polymerization by chromic acid

Abstract

The effect of chromic acid on the polymerization of acrylonitrile, methyl acrylate and methyl methacrylate initiated by ceric perchlorate in HClO₄ medium at 35°C was studied. Monomer conversion decreased considerably (from ca. 47 to ca. 9%) by the addition of small amounts of Cr(VI) (∼10⁻⁴M). The dependence of Rp, the rate of total metal ion (Cr^6⊕ + Ce^4⊕) disappearance and P̄ on the various variables suggested that the initiation occurred by Ce^4⊕ and termination by both Ce^4⊕ and ceric-chromate complex. The formation of the latter was supported by spectrophotometric studies. The ratios of the rate constants for termination by the complex and by ceric ion for the three monomers were evaluated. The results showed that the complex was a more powerful oxidant than either Ce(IV) or Cr(VI).