Abstract
N-Methylpyridinium esters derivatives of 2-methylbenzothiazole hemicyanine dyes photoinitiators/photosensitizers derived from N-propyl-3-[N-2-methylbenzothiazolo]-4-pyridyno phenylacetic acid ester diiodide and N-propyl-3-[N-2-me]thylbenzothiazolo]-4-pyridino diphenylacetic acid ester diiodide were synthesized and proposed as new photoinitiators of polymerization of 2-ethyl-(2-hydroxymethyl)-1,3-propanediol triacrylate under argon laser exposure at 514 nm. These compounds exhibit a strong absorption around 520 nm. The dye/borate salt, dye/borate salt/N-methoxypyridinium salt, dye/borate salt/diphenyliodonium salt, and dye/borate salt/1,3,5-triazine derivative combinations are very efficient in initiating of radical photopolymerization of triacrylate. Excellent polymerization profiles were obtained. The effect of both sensitizer and co-initiator structure on the ability to initiate of free radical polymerization of photoinitiating systems was also presented. The mechanism was discussed for different multicomponent initiating systems. Graphical Two-cationic 2-methylbenzothiazole derivatives as green light absorbed sensitizers in initiation of free radical polymerization.
Highlights
Among different polymer synthesis approaches, the free radical photopolymerization is a fast and efficient method for theIn almost all cases of three-component systems, electron donating compounds are designed to decompose after electron transfer in order to prevent unwanted back electron transfer in the (D−S+) dye-donor contact ion pair
It should be noted that their photoinitiating ability is lower than wellknown commonly used photoinitiators operating in the visible light region [3, 4, 24, 26]
On the basis of the photochemistry of borate anion [29, 30], photochemistry of N-alkoxypyridinium cation [18], photochemistry of 1,3,5-triazine derivatives [31,32,33], and photochemistry of iodonium salt [24], as well as results of nanosecond laser flash photolysis described in our previous papers [5, 15, 17, 19], we propose the mechanism of primary and secondary processes occurring in three-component photoinitiating systems (Scheme 3)
Summary
In almost all cases of three-component systems, electron donating compounds are designed to decompose after electron transfer in order to prevent unwanted back electron transfer in the (D−S+) dye-donor contact ion pair. This side reaction gives back the reactants and is a loss of energy. Decomposable electron acceptors prevent bimolecular radical ion recombination after electron transfer. Those unstable electron acceptors decompose or dissociate after electron transfer and generate radicals Those systems provide excellent results because these acceptors prevent undesirable recombination process and produce new secondary radicals, which enhance the photoreactivity toward free radical polymerization [4].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
