Synthesis and cationic ring-opening polymerization of 2-methylene-7-oxabicyclo[2.2.1]heptane

A new unsaturated bicyclic ether, 2-methylene-7-oxabicyclo[2.2.1]heptane (4) was synthesized by successive Diels-Alder addition of furan to acrylonitrile, hydrogenation of cyano compound 5, and Hofmann degradation of the quaternary ammonium hydrate 7 derived from the amine 6. Cationic polymerization of the monomer 4 was carried out in CH2Cl2 using BF3 · OEt2, PF5, SbCl5 and SnCl4 as catalysts in the temperature range of −20 to −25°C. White or slightly yellow powdery polymers of low molecular weight were obtained with PF5 and BF3 · OEt2 as catalysts, while no polymer was obtained with SbCl5 and SnCl4 as initiators. The IR, 1H and 13C NMR spectra of the polymers indicated that they consist of three kinds of repeating units, that is, two unsaturated units caused by ring-opening polymerization and one addition unit. Using proton NMR data of the polymers, the distribution of repeating units was calculated. A polymerization mechanism is proposed. The thermal stability of the obtained polymers is discussed.