Picosecond flash photolysis of high-speed photoinitiator systems

Abstract

The sensitization mechanism of a sensitizer dye, 2-[p-(diethylamino)styryl]naphtho-[l,2,d]thiazole (DNT), with a radical-generating reagent, 3,3',4,4'-tetrakis(tert-butyldioxycarbonyl)-benzophenone (I), in toluene has been investigated by picosecond laser Hash photolysis. In the absence of I, the fluorescence of DNT with a decay time of 100 ps, a rapidly decaying transient absorption with a decay time of 100 ps corresponding to the decay time of the fluorescent singlet excited state, and an unknown slowly decaying absorption with a decay time of 6 ns were detected. However, no transient absorption of the triplet was detected. In the presence of I, the rapidly decaying absorption and fluorescence were not quenched by I, but the slowly decaying absorption was quenched at a quenching rate K_q = 5 x 10¹⁰dm³/mol s, which was almost the same as the diffusion-controlled rate. The results suggested that the sensitization of I proceeded from the non-radiative transient state of DNT with a decay time of 6 ns in toluene.

Key Words:

• Picosecond flash photolysis
• Photoinitiator
• Sensitization
• Photopolymrization