PHOTOCHEMISTRY AND PHOTOINITIATOR PROPERTIES OF 2-SUBSTITUTED ANTHRAQUINONES .2. PHOTOPOLYMERIZATION AND FLASH-PHOTOLYSIS

Citation
Ns. Allen et al., PHOTOCHEMISTRY AND PHOTOINITIATOR PROPERTIES OF 2-SUBSTITUTED ANTHRAQUINONES .2. PHOTOPOLYMERIZATION AND FLASH-PHOTOLYSIS, Polymer, 36(24), 1995, pp. 4665-4674
Citations number
9
Categorie Soggetti
Polymer Sciences
Journal title
ISSN journal
00323861
Volume
36
Issue
24
Year of publication
1995
Pages
4665 - 4674
Database
ISI
SICI code
0032-3861(1995)36:24<4665:PAPPO2>2.0.ZU;2-7
Abstract
The photoinduced polymerization activities of fifteen 2-substituted an thraquinones have been determined in different monomers and prepolymer s using real-time Fourier-transform infra-red spectroscopy and photoca lorimetry. The relative order in photoinitiator efficiency is found to be highly dependent upon the method used, the nature of the light sou rce, amine co-synergist and monomer being crucial factors. Oxygen quen ching in all cases indicates that the triplet state is the active prec ursor. Without an amine co-synergist, absolute quantum-yield measureme nts show that anthraquinones with electron-withdrawing groups are more active than those which are electron-donating. However, in the presen ce of a tertiary amine and under polychromatic illumination, the effec ts are different. In the latter case amido derivatives with long-wavel ength charge-transfer bands and mixed n pipi pi* triplet states tend to be more reactive. Fluorescence and phosphorescence analyses indicat e a high rate of intersystem crossing to the triplet state. The relati ve positions of the lowest excited singlet pi pi and second excited n pi triplet states play an important role in determining their photoa ctivities, as shown in paper 1. Seraiquinone radical and radical-anion intermediates are observed using microsecond flash phorolysis and the data interrelated to their spectroscopic and photopolymerization acti vities. The haloanthraquinones are shown to undergo an additional mech anism involving dehalogenation.