화학공학소재연구정보센터
Journal of Polymer Science Part A: Polymer Chemistry, Vol.54, No.13, 1945-1954, 2016
2,2,2-Trifluoroacetophenone-Based D-pi-A Type Photoinitiators for Radical and Cationic Photopolymerizations Under Near-UV and Visible LEDs
Two D-pi-A-type 2,2,2-trifluoroacetophenone derivatives, namely, 4'-(4-(N,N-diphenyl)amino-phenyl)-phenyl-2,2,2-trifluoroacetophenone (PI-Ben) and 4'-(4-(7-(N,N-diphenylamino)-9,9-dimethyl-9H-fluoren-2-yl)-phenyl-2,2,2-trifluoroacetophenone (PI-Flu), are developed as high-performance photoinitiators combined with an amine or an iodonium salt for both the free-radical polymerization of acrylates and the cationic polymerization of epoxides and vinyl ether upon exposure to near-UV and visible light-emitting diodes (LEDs; e.g., 365, 385, 405, and 450 nm). The photochemical mechanisms are investigated by UV-Vis spectra, molecular-orbital calculations, fluorescence, cyclic voltammetry, photolysis, and electron-spin-resonance spin-trapping techniques. Compared with 2,2,2-trifluoroacetophenone, both photoinitiators exhibit larger redshift of the absorption spectra and higher molar-extinction coefficients. PI-Ben and PI-Flu themselves can produce free radicals to initiate the polymerization of acrylate without any added hydrogen donor. These novel D-pi-A type trifluoroacetophenone-based photoinitiating systems exhibit good efficiencies (acrylate conversion 548%-66%; epoxide conversion 585%-95%; LEDs at 365-450 nm exposure) even in low-concentration initiators (0.5%, w/w) and very low curing light intensities (1-2 mWcm(-2)). (C) 2016 Wiley Periodicals, Inc.