名称:
Near UV–vis LED-excitable two-branched sensitizers for cationic, radical, and thiol-ene photopolymerizations
摘要:
Two novel branched sensitizers bearing biphenyl or fluorenyl groups as the linking skeleton and triphenylamine-stilbene-thiomethyl benzonitrile as peripheral branches were designed. Strong absorption of light in the UV-vis range (lambda(max) = 389-397 nm, epsilon(max) = 60,200-90,300 M-1 cm(-1)) matched the emission of new light sources, i.e., UV-vis light-emitting diodes at 365-450 nm. The reactive species produced from the photoinitiating systems based on these chromophores themselves or combined with an iodonium salt, N-vinylcarbazole, or an amine were highly efficient for versatile photopolymerizations (radical, cationic, and thiol-ene polymerizations) upon soft exposure conditions (365-450 nm light emitting diodes). The UV-vis spectra, theoretical calculation of molecular orbitals, electrochemistry, and fluorescence quenching measurements were studied to reveal the photochemical mechanism. (C) 2015 Elsevier Ltd. All rights reserved.