Cationic polymerization of α,β‐disubstituted olefins. XV. Stereospecific polymerization of butenyl ethers by cationic catalysts

Methyl, ethyl, and isopropyl butenyl ethers, CH3CH2CHCHOR, were polymerized with homogeneous catalysts at −78°C. Toluene, methylene chloride, and nitroethane were used as solvents, and BF3O(C2H5)2 and SnCl4·CCl3CO2H were used as catalysts. The stereoregularity of the polymers were compared by x‐ray diagrams and infrared absorption ratios. The stereoregularity of polymers increased with increasing content of the trans isomer in the monomer and with increasing polarity of the solvent. In the polymerization of methyl and ethyl butenyl ethers, crystalline polymers were obtained from both the trans and cis isomers. The crystalline polymer prepared from the trans isomer and that from the cis isomer had the same steric structure. This behavior is quite different from that observed in the polymerization of propenyl ethers. It is concluded that the bulkiness of the group on the olefinic β‐carbon plays an important role in the stereospecific polymerization of α,β‐disubstituted olefins.