Cationic polymerisation of exo‐2‐methyl‐7‐oxabicyclo‐[2.2.1]‐heptane: The catalytic system fecl3—socl2

The nature of the acceleration period which is found in the polymerisation of exo‐2‐methyl‐7‐oxabicyclo‐[2.2.1]‐heptane with FeCl3—SOCl2, when R = [FeCl3]/[SOCl2] is above a certain limit, has been investigated. By means of a conductometric study of the reactions occurring in C2H4Cl2/diethylether mixture (6:1 by volume), between FeCl3 and SOCl2, it has been possible to show that this acceleration period is related to a slow formation of ionic species, from which the chain carriers are formed. When the catalyst/cocatalyst mixture was allowed to stand until equilibrium was attained before it was added to the monomer solution, no acceleration period was detectable. The kinetic study of the polymerisation was then extended to the whole range of catalyst/cocatalyst ratios. It has been shown that the ion SO2⊕ which is present when [FeCl3] is higher than [SOCl2] is not able to initiate the polymerisation. If R is ⪖ 5 there is no polymerisation, whatever the [FeCl3]. If R is less than 5 but more than about 2, the polymerisation practically stops at partial conversion. When R is well below 1 the time‐conversion curves give good second order plots indicating a stationary state condition.