LASER FLASH-PHOTOLYSIS IN HIGH-SPEED PHOTOPOLYMER COATING LAYERS - EFFECTS OF INCORPORATING DIMETHYL PHTHALATE AS A PLASTICIZER INTO COATING FORMULATION

The sensitization mechanisms of ketocoumarin dyes with a radical-gener ating reagent, 10, lbis[1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H, 11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one] (KCD-J), 7,7']-bis(diet hylamino)-3,3'-carbonyldicoumarin (KCD-DA) with 3,3',4,4'-tetrakis(t-b utyldioxycarbonyl) (I) in poly(methyl methacrylate) film containing di methyl phthalate (DMP) as a plasticizer have been investigated by lase r flash photolysis using a total reflection cell. The fluorescence of the dyes was efficiently quenched by I in PMMA containing 50 wt% of DM P (film A) against total solid with static quenching distances of 12.5 and 12.7 Angstrom for KCD-J and KCD-DA. The static quenching distance was around 1.5 times longer than that in PMMA. The decay time of the triplet in a film A was slightly quenched by I with a k(q) of less tha n 1.5 x 10(6) mol(-1) dm(3) s(-1) for KCD-J and KCD-DA. These results show that a static singlet sensitization from the fluorescent excited dyes to I is the predominant process in film A, suggesting the same pr edominant static singlet sensitization process in a PMMA film containi ng acrylate monomer, and the static quenching distance is increased by incorporation of DMP into PMMA film.