Polymerization of butadiene by polybutadienyllithium in the presence of tetrahydrofuran

Polymerization of butadiene by polybutadienyllithium (PBLi) has been studied in THF for concentrations of PBLi between 10^?4 and 10^?2 mol/I in the range 20–70°, and also in a non-polar medium using THF as an added electron donor at various THF/PBLi ratios. The kinetic order with respect to PBLi in THF was 0.5 and the activation energies of the overall process and the propagation on free carbanions were 7.5 and 6.7 kcal/mol respectively. Rate constants for propagation on the free carbanions were calculated at three temperatures and rate constants for propagation on contact ion pairs were determined at two THF/PBLi ratios. Data on the kinetics of polymerization and the microstructure of the polymers suggest that contact ion pairs and free carbanions participate in propagation reactions.