Panchromatic Type II Photoinitiator for Free Radical Polymerization Based on Thioxanthone Derivative

Abstract

A new photoinitiator for free radical photopolymerization, belonging to the thioxanthone derivatives, was synthesized and characterized. It was found that the compound absorbs over the whole UV–vis spectrum with relatively high absorption coefficients. Fluorescence studies reveal that three different singlet excited states are responsible for this absorption. Phosphorescence and laser flash photolysis evidence the formation of a triplet state from which a photoreduction can occur. Consequently, initiating radicals were formed which are able to initiate the photopolymerization of methyl methacrylate in DMF. Finally, the photopolymerization of acrylates was performed in film at different wavelengths such as 392, 476, 532, and 632 nm, emphasizing the possibility to use this novel photoinitiator when panchromatic irradiation is required.

A new role of curcumin: as a multicolor photoinitiator for polymer fabrication under household UV to red LED bulbs

“…1,2 Among these, multicolor photoinitiators with panchromatic light absorption are extremely interesting, as they can utilize various wavelengths of incident light (from UV to red light) to initiate the polymerization of photocurable formulations despite containing other light absorbing compounds inside. However, very few multicolor photoinitiators have been reported, including 2,7-di-tertbutyldimethyldihydropyrene, 10 indoline and squaraine dyes, 11 thiophene derivatives, 12 novel thioxanthone derivative, 12 indanedione derivative, 13 thioxanthone derivative 14 and the combination of different light absorbing perylene derivatives. 15 The synthesis of these reported compounds is complicated, and they have been applied mainly in cationic or thiol-ene photopolymerizations.…”

Dual ligand-based fluorescence and phosphorescence emission at room temperature from platinum thioxanthonyl complexes

“…The ready formation of the 3 ππ*-and 3 nπ*-states of aromatic carbonyl compounds after photoexcitation into the 1 π→π*-and 1 n→π*-bands [81][82][83][84] renders thioxanthone derivatives useful sensitisers 85,86 or initiators for radical photopolymerisations of olefins. [87][88][89][90][91][92][93] The excited states of thioxanthones involve two singlet states S 1 ( 1 ππ*) and S 2 ( 1 nπ*) and two corresponding triplet states T 1 ( 3 ππ*) and T 2 ( 3 nπ*), which readily equilibrate (Fig. 1).…”

Studies of the binding mode of TXNHCH 2 COOH with calf thymus DNA by spectroscopic methods

“…TXNHCH 2 COOH (2-(9-oxo-9H-thioxanthen-2ylamino) acetic acid) was synthesized as reported in the literature [49,50].…”