Photochemistry of 2-acetoxy and 2-acryloxythioxanthone and copolymers with methylmethacrylate: A conventional and laser flash photolysis study

摘要: Abstract The photochemistries of the monomer 2-acryloxythioxanthone and its copolymers with methyl methacrylate have been examined compared that a model 2-acetoxythioxanthone using both conventional microsecond nanosecond laser flash photolysis in variety solvent systems. On tetrahydrofuran, transient absorption spectra are produced maxima at 300 420 nm (assigned to ketyl radical) together weak, broad tail extending longer wavelengths due radical-anion. Transient absorbances reduced non-hydrogen atom donating acetonitrile apart from copolymer intramolecular hydrogen abstraction. intensities follow order > 8% 21% copolymer. Intramolecular self-quenching is believed be an important process here effect tertiary amine (diethylethanolamine) being variable. acetonitrile, 330, 440 630 assigned triplet-triplet (21%). triplet strongly self-quenching. presence enhances absorptions 330 for thioxanthones exciplex formation but quenched by addition monomer. more pronounced than again strong quenching observed At significantly increased because electron transfer within give In case copolymer, only slight increase this region coiling polymer chain sterically impairs amine. Concentration studies on decays show whilst intermolecular interactions model, some degree other hand, (21%), rate constant decrease increasing concentration solution cage effects enhancing lifetime. various amines linear correlation between first-order constants ionization potential amine, confirming importance via formation. these results photo-initiated polymerization discussed.