The Ring-opening Polymerisations of Cyclic Olefins

Abstract

The ring opening polymerisations of cyclic olefins were investigated using a catalyst system of tungsten hexachloride and aluminium tri-isobutyl. The cyclic olefins investigated were cyclooctene and cyclopentene. The monomers were purified and attempts were made to remove conjugated dienes that were found to be present in the monomers. The rates of the polymerisation reactions were followed using dilatometric techniques. It was found that the rates of polymerisation were dependent upon: (i) the order of the addition of the catalyst components. The tungsten compound was added to the monomer before the aluminium compound to give the greatest rate of polymerisation; (ii) the time that elapsed between the addition of the tungsten compound to the monomer and the addition of the aluminium compound to the mixture; (iii) the concentrations of the monomer and the catalysts and the molar ratio of the catalyst components. The kinetics of the polymerisation reaction were considered and a series of reactions were proposed in which two tungsten complexes were formed which then combined with the aluminium compound to form two active species. A kinetic chain scheme was proposed which correlated the results obtained in this project with the results of previous workers. A mechanism was proposed to account for the deactivation of the polymerisation by the presence of conjugated dienes. The polymerisation mechanism was discussed in terms of the molecular orbital theory of bonding.