Polymerisation of vinyl monomers by transition metal benzyl compounds. Part II. Polymerisation of styrene by tetrabenzyl zirconium

Abstract

Abstract The polymerisation of styrene by tetrabenzyl zirconium in toluene in the dark at 30 and 40°C has been studied using kinetics, spectroscopic and radiochemical techniques. From the data obtained, together with information derived from molecular weight measurements, a mechanism has been obtained which is in accord with the experimental findings. The polymerisation is of the coordinated anionic type in which only one of the four zirconium benzyl bonds is activated for polymerisation. Each active metal centre grows only one chain and is terminated by a β‐hydrogen abstraction process or by a bimolecular reaction involving monomer. Transfer reactions are absent. Only a small fraction of the catalyst participates in polymerisation and the concentration of active polymerisation centres is very low. A complex between tetrabenzyl zirconium and coordinated monomer could not be detected experimentally. Values for the velocity constants for initiation, propagation and termination are determined.