Dye-sensitized Photopolymerization of Vinyl Compounds. Polymerization of Styrene by Cyanine Dyes. III

Abstract

Abstract Extensive studies on the photopolymeri-zation of styrene by virtue of cyanine dyes were performed and it was reconfirmed that only the chain initiation is promoted by the direct interaction between the excited dye and the styrene molecule. Activation energies for the photochemical initiation process were experimentally determined for several dyes of iodide, bromide and chloride. In general the activation energy depends on the kind of halogen ion and from this result it was concluded that halogen ion plays an essential rôle in the reaction. A general tendency was observed that the activation energy diminishes as the wavelength of absorption maximum of dyes becomes shorter. A plausible scheme for the chain initiation process was given, in which an electron transfer from X− to D+ is involved in the process of activation.