Cationic polymerization of α,β‐disubstituted olefins. Part 17. Effect of polymerization conditions on the reactivity of alkenyl ethers relative to vinyl ethers

<jats:title>Abstract</jats:title><jats:p>In order to clarify the propagation reaction, vinyl ether was copolymerized with the corresponding alkenyl ether under various conditions. <jats:italic>cis</jats:italic>‐Propenyl ether (<jats:italic>cis</jats:italic>‐PE) was several times more reactive than <jats:italic>trans</jats:italic>‐PE and the corresponding vinyl ether in the copolymerization catalyzed by BF<jats:sub>3</jats:sub> · O(C<jats:sub>2</jats:sub>H<jats:sub>5</jats:sub>)<jats:sub>2</jats:sub> in toluene. However, the reactivity of <jats:italic>cis</jats:italic>‐PE relative to <jats:italic>trans</jats:italic>‐PE and the vinyl ether was found to be greatly decreased with increasing polarity of the solvent and to be very close to unity in such polar solvents as nitroethane. On the other hand, the reactivity of <jats:italic>trans</jats:italic>‐IBPE relative to IBVE was scarcely changed by polymerization conditions. Also, the nature of the initiator and polymerization temperature affect the reactivity of <jats:italic>cis</jats:italic>‐PE relative to the vinyl ether. These phenomena were explained by the relative stability of the bridged and open car bonium ions based on the polarity of the solvent and steric hindrance due to substituents in the <jats:italic>trans</jats:italic> isomer.</jats:p>