Structure and reactivity α,β‐unsaturated ethers. II. Cationic copolymerizations of propenyl isobutyl ether

Abstract cis‐ and trans‐Propenyl isobutyl ethers were copolymerized with each other and each with vinyl isobutyl ether separately under various conditions. In homogeneous polymerizations a cis‐β‐methyl substitution on vinyl isobutyl ether apparently enhanced the reactivity, whereas the trans substitution tended to reduce it slightly. In heterogeneous catalysis, on the other hand, a β‐methyl group on the vinyl ether, whether cis or trans, greatly reduced the reactivity, probably because of the steric hindrance toward the adsorption of monomers on the catalyst surface. The relative reactivities of cis‐ and trans‐propenyl isobutyl ethers ranged from 2 to 20, depending on the polymerization conditions. The polymer end formed from the cis monomer exhibited special steric effects. It was concluded that even in homogeneous media the rotation of the polymer end around the terminal carbon–carbon bond is restricted.