Photoinitiated cationic polymerization of vinyl ethers using substituted vinyl halides

The photoinitiated cationic polymerization of typical vinyl ether monomers, such as isobutyl vinyl ether, di(ethylene glycol) divinyl ether, tri(ethylene glycol) divinyl ether, 1,4-butanediol divinyl ether, and 1,6-hexanediol divinyl ether, by use of aryl-substituted vinyl halides was studied. The cationic polymerization of these monomers was initiated at 0 °C or room temperature upon irradiation at λ = 350 nm in CH₂Cl₂ solutions with one of the following compounds: 1-bromo-l,2,2-tris(p-methoxyphenyl) ethene, 1-bromo-l-(p-methoxyphenyl)-2,2-diphenylethene, 1-bromo-1,2,2-triphenylethene, and 1-chloro2,2-bis(p-methoxyphenyl)ethene in the presence of zinc iodide (ZnI₂). A mechanism involving formation of an adduct between the monomer and the products yielded from the photoinduced homolysis of the vinyl halide followed by electron transfer is proposed. In the subsequent step, the terminal carbon-halide bond in this adduct is activated by the coordinating effect of Znl₂. This polymerization exhibited some characteristics of pseudoliving cationic polymerization.