Evaluation of sensitizing ability of barbiturate-functionalized non-ionic cyanine dyes; application for photoinduced radical generation system initiated by near IR light

The sensitizing abilities of near infrared (near IR)-absorbing ionic (D1) and non-ionic (D2 and D3) cyanine dyes in a photoinduced radical polymerization system were evaluated. The solubility in an organic solvent of non-ionic cyanine dyes is much higher than that of an ionic cyanine dye. The photoinduced radical polymerization system consists of a sensitizing dye (D1–D3), 2,4,6-tris(trichloromethyl)-s-triazine (TCT, as a radical genetrator), and a poly-functional acrylate monomer (DPHA) in the binder polymer. All dyes showed a sensitizing ability in the photoinduced radical polymerization systems by near IR light. Non-ionic cyanine dyes, D2 and D3, showed a higher sensitizing ability than D1. From the IR and UV–vis studies, it was revealed that the high sensitizing ability of D2 and D3 is a result of an interaction between the dye and TCT in the polymer matrices, promoting the electron-transfer from the dyes to the TCT.