| Abstract: | The monomer series, o-, m-, and p-(2-vinyloxyethoxy)-β-nitrostyrenes, was studied. All three monomers were selectively polymerized through the electron-donating vinyloxy group via cationic initiation. The linear polymers from the meta and para isomers containing the electron-accepting nitrovinyl group were readily crosslinked via anionic initiation. The polymer derived from the ortho isomer was not crosslinked by this mechanism, an observation in accord with results previously reported from these laboratories in which it was shown that all o-substituted-β-nitrostyrenes having ortho substituents larger than fluorine exhibited a sterically inhibited propagation step. The meta and para isomers of this series were selectively polymerized through the electron-accepting nitrovinyl group via anionic initiation. Because of the fact that the resulting polymers were soluble only in highly polar solvents, subsequent crosslinking of these polymers via cationic initiation could not be accomplished. However, these polymers showed strong tendencies to undergo crosslinking upon long exposure to air. Because of the sterically induced ortho effect referred to above, no significant polymerization occurred in the case of the ortho isomer of this series via anionic initiation. However, it was shown in this case that initiation via the anion was rapid, and that the slow step was propagation. |
