The Effect of Cr2+ on the Termination of Radical Polymerization

Styrene (St) was pelymerized when the divalent chromous acetate, (Cr2+)-CHCIs system was used as initiator. In the case of [Cr2+]/[CHC13] 20, the rate of polymerizatien decreased with increasing [Cr2+].The termination reaction with Cr2+ was studied in detail using a, a'-azobisisobutylonitrile (AIBN) as initiator in the presence of Cta2+. The rate of polymerization decreased with increasing Cr2+ and the rate constant of termination reaction of polystyryl radicalwith Cr2+ was found to be 74.61/molosec. Whereas, the polymerizations of methyl methacrylate and acrylonitrile were inhibited by Cr2+. This difference of termination effects was discussed in terms of the e value of the monomers.Due tothe combination of Cr2+ with p-benzequinone(P-BQ), it was found that the termination effects of Cr2+ and p-BQ disappeared, because P-BQ reacted with Cr2+ to produce an inert oxidation product.