Polymerization of isoprene in benzene initiated by polyisoprenyl lithium

Abstract

Polyisoprenyl lithium free from n-butyl lithium was prepared from isoprene and n-butyl lithium in benzene. This was used to initiate the polymerization of further isoprene. Kinetic studies at various initial concentrations of polyisoprenyl lithium [PLi]₀ and isoprene [M]₀ were carried out at 35.1°C and less extensively at 25.2 and 45.2°C. The results at 35.1°C are summarized in the equation –d[M]/dt =k′[PLi]^r₀[M], where [M] represents the concentration of isoprene at time t and r lies between 0.21 and 0.40 with a probability of 0.9. Consideration of the random and systematic errors suggests that the most likely integral value of the degree of association of polyisoprenyl lithium is 4.