ISSN:
0887-624X
Keywords:
excited state
;
thioxanthene
;
derived dye
;
photopolymer plates
;
photoinitiators
;
photopolymerization
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The excited state interactions occurring when a three-component system of thioxanthene derived dye TXD/amine/additive (diphenyliodonium salt, CBr4, benzoyl peroxide, cumene hydroperoxide) is subjected to sensitization processes in the visible range, were investigated through time-resolved absorption spectroscopy, spectrofluorometry, and photolysis. The rate constants of the various operative processes were measured together with the values of the fluorescence quantum yields (e.g. φ f = 0.75 ± 0.07 in methanol) and the lifetimes of the singlet excited state of the dye (e.g. 6 ns in methanol). Singlet state quenching by methyldiethanolamine (MDEA) occurs with a rate constant k = 109 M-1 s-1 in methanol. The reactivity of the triplet excited state of the dye is very low (k = 5.6 × 104 M-1s-1 for the TXD/MDEA interaction). The ketyl radicals that arise from the interaction of the singlet state of the dye with the amine, are quenched by such additives as CBr4 (k = 6.7 × 105M-1s-1), or the onium salts (k = 5.7 × 105M-1 s-1). The calculations of the yields of interaction of the singlet state of the dye with the two components of the system demonstrate that the process of quenching by the amine is the main one (φint = 0.5) compared to that by, e.g., an onium salt (φint = 0.07). Sensitivity of 0.3 mJ cm-2 obtained in a laser scanning system is also reported. © 1996 John Wiley & Sons, Inc.
Additional Material:
33 Ill.
Type of Medium:
Electronic Resource
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