Polymerizability of asymmetric azines bearing bicyclic substituents

Abstract

To investigate the polymerizability of asymmetric azines, (1R)-(−)-fenchone formaldehyde azine (Az 1), (1R)-(+)-camphor formaldehyde azine (Az 2), formaldehyde (1R)-(+)-nopinone azine (Az 3) and formaldehyde norcamphor azine (Az 4) were prepared and their polymerizabilities were examined using radical, anionic and cationic initiators. The polymerizability of these asymmetric azines strongly depends on the bulkiness of the bicyclic substituent. The azines bearing more bulky substituents (Az 1 and Az 2) exhibit poor polymerizabilities presumably because of their steric hindrance. In cationic and anionic polymerizations of the least sterically hindered azine (Az 4), the monomer conversions were high, but the molecular weights of the products were very low, indicating that active species in the polymerizations of Az 4 are so labile that chain transfer reactions or side reactions dominate over propagation. Among these asymmetric azines, Az 3 is the most promising monomer with respect to the bulkiness of the bicyclic substituent, because oligomer of M w 2.4 × 103 was produced by cationic polymerization of Az 3 initiated by TiCl4 in CH2Cl2 at−20°C. Elemental analysis and spectroscopic data indicated that the oligomer was formed by addition polymerization through the CH2=N bond in Az 3.