Photoinitiated cationic polymerization of vinyl ethers using substituted vinyl halides in the presence of metallic zinc

A novel photoinitiation approach for Lewis acid-catalyzed cationic polymerization of vinyl ethers, based on in situ formation of zinc halide, has been developed. The proposed mechanism of photoinitiation involves photoinduced generation of vinyl cations from subtituted vinyl halide, 1-bromo-1,2,2-tris(p- methoxyphenyl)ethene, by electron transfer and subsequent reaction with the monomer to form an adduct. In the process, zinc bromide, which plays central role in propagation step, was generated simultaneously by the reaction of metallic zinc with the photochemically produced bromine radicals. The living nature of the polymerization was studied by the investigation of time dependence of logarithmic conversion and molecular weights. The capability of the photoinitating system to induce cross-linking was also demonstrated using various difunctional monomers.