Metathetic Polymerisation of Cyclic Alkenes

Abstract

The monometallic initiation of the ring opening polymerisation of cyclopentene as a solution in toluene or chlorobenzene has been investigated by dilatometric and calorimetric techniques using WC16or WC16/02, as the catalyst. These studies indicated the occurrence of a series of reactions between cyclopentene and tungsten hexachloride and that the kinetic behaviour of the system and the products of the reaction depended on the solvent used. The kinetic behaviour of WC16/ cyclopentene system in toluene was complex; the dependence of the rate of polymerisation on the concentration of tungsten hexachloride showed a maximm. Deviations from simple kinetics were associated with the slow formation of an oily precipitate. In the chlorobenzene system the products of the reactions remained soluble and the kinetics of the polymerisation have been interpreted in terms of one of the intermediate products of the series of reactions acting as active species for the metathesis polymerisation of cyclopentene. Spectrophotometric studies have been used in chlorobenzene to elucidate the kinetic nature of the reaction involved in the system. Based on this technique and by use of computer simulation a kinetic scheme has been postulated and the rate constants obtained from these studies have been applied to dilatometric results to explain many of the features of the polymerisation. According to this kinetic scheme the active species is most likely removed from the system by a bimolecular termination reaction. It was found that oxygen could only have a very effective cocatalyst activity if the system was heterogeneous where the source of activity before the addition of oxygen could remain dormant and the active centres produced on the addition of oxygen to the system insoluble. Polymerisation of n-butyl vinyl ether initiated by a metathesis active species indicated that the metathetically active species could be ionic in nature.