SynopsisIsoprene was polymerized at 30°C with VC4-AlEt2Br catalyst system in n-hexsne. A linear dependence of rate of polymerization on the monomer and catalyst concentrations W M found. Infrared spectra of polyisoprene showed the presence of cyclic structure, indicating a cationic mechanism of polymerization.The overall activation energy was 8.96 kcal/mole.