Benzoin type photoinitiator for free radical polymerization

Abstract

Benzoin, a popular photoinitiator for free radical polymerization of vinyl monomers, was improved by introduction of two methyl thioether substituents. This new benzoin derivative showed an about 50 times higher light absorption in the near-UV spectral region and performed better than the unsubstituted benzoin in polymerization experiments in bulk solutions or films of acrylate monomers when low initiator concentrations are used. Laser flash photolysis, low temperature luminescence experiments and photoproduct studies by mass spectrometry suggest that a slow a-cleavage mechanism (k a ¼ 2.2 Â 10 5 s À1) from the electronic triplet state with a quantum yield of 0.1 is the primary photoreaction to generate the initiating free radicals.

Visible light sensitive photoinitiating systems: Recent progress in cationic and radical photopolymerization reactions under soft conditions

“…Significant progress has been made in the design of high-performance PIs (and PISs) for FRP under UV lights [28][29][30][31][32][33][34][35][36][37][38][39][40][41] and visible lights [14,. Several attempts have also been made for the cationic PISs under long wavelength UV lights (>300 nm) [73][74][75][76][77][78][79][80][81][82][83] or even visible lights [84][85][86][87][88][89][90][91][92][93][94].…”

Versatile light‐responsive organogels: Evaluation of their dye releasing and photoinitiation behaviors

“…Photoinduced radical polymerization technique has been employed in extensive applications, such as curing of polymeric coatings, polymers with controlled molecular weights, linear and branched copolymers, and single‐chain nanoparticles . Free‐radical photoinitiators consist of two particular classes: (a) type I that undergoes direct photolysis and widely used in various UV applications and (b) type II photoinitiators, which possess longer wavelength absorption compared to type I initiators . Benzophenone is a conventional photoinitiator used in various UV‐curing applications such as printing inks, production of 3D objects, and coatings.…”

LED‐Induced Polymerization (385, 405, and 455 nm) Using Star‐Shaped Tris(4‐(thiophen‐2‐yl)phenyl)amine Derivatives as Light‐Harvesting Photoinitiators

“…Very recently, an increasing number of near‐UV/visible light‐sensitive photoinitiating systems (PIS) have been developed either for free radical photopolymerization (FRP) or cationic photopolymerization (CP) . It is highly interesting to move forward in this charming subject and look for novel structures to be used as high‐performance PIs in both FRP and CP especially under near‐UV or visible light‐emitting diodes (LEDs) that are increasingly used.…”

“…Very recently, an increasing number of near-UV/visible light-sensitive photoinitiating systems (PIS) have been developed either for free radical photopolymerization (FRP) or cationic photopolymerization (CP). [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] It is highly interesting to move forward in this charming subject and look for novel structures to be used as high-performance PIs in both FRP and CP especially under near-UV or visible lightemitting diodes (LEDs) that are increasingly used. In recent years, we have developed a number of original photoinitiators (PIs) and PIS that can operate in the 365-700 nm wavelength range under Xe-Hg or Xe lamps, laser diodes, LEDs, and household devices (see for example the reviews in refs.…”