Benzyl, ethyl, and deuterated ethyl propenyl ethers (BzPE, EPE, and EPE‐d5, respectively) with different cis/trans isomer ratios were polymerized by BF3O(C2H5)2 at −78°C in toluene, methylene chloride, and nitroethane solvents. Poly(propenyl alcohol) [poly(PA)] was also prepared by treating poly(BzPE) with HBr gas. The steric structure of these polymers was studied by 1H‐ and 13C‐NMR spectroscopy. The poly(EPE‐d5) obtained from a trans‐rich monomer mixture was crystalline, while one from a cis‐rich monomer mixture was amorphous. Poly(BzPE) was always amorphous. Poly(BzPE), poly(PA), and poly(EPE‐d5) gave 1H‐NMR spectra with two β‐methine peaks, relative intensities of which depended on the geometric structure of the monomers. Their spectra of β‐methyl protons decoupled from β‐methine proton were also split into two peaks, relative intensities of which corresponded to those of the two α‐methine peaks. 13C‐NMR spectra of α‐OCH2 and β‐CH3 of poly(EPE), respectively, consisted of two peaks. These observations show that the poly(propenyl ethers) examined, whether crystalline or amorphous, have only two dyad structures (probably threo or erythro‐meso and racemic), and that their α‐ and β‐carbons have the same dyad structure, irrespective of the kind of the alkoxyl groups.
synopsisMethyl, ethyl, and isopropyl butenyl ethers, CH&H&H=CHOR, were polymerized with homogeneous catalysts at -78°C. Toluene, methylene chloride, and nitroethane were used as solvents, and BF~O(CZH~)Z and SnClr-CClsC02H were used as catalysts. The stereoregularity of the polymers were compared by x-ray diagrams and intrared 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 8-carbon plays an important role in the stereospecific polymerization of a,&disubstituted olefins.
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