Novel N-ethyl-2-styrylquinolinum iodides as sensitizers in photoinitiated free radical polymerization of trimethylolopropane triacrylate (TMPTA), part 3

摘要

Three-component systems, which contain a light-absorbing species (dye), an electron donor (n-butyltriphenylborate salt), and a third component (N-alkoxypyridinum salt or 1,3,5-triazine derivative), have emerged as efficient, visible-light sensitive photoinitiators of free radical polymerization. It was found that three-component systems are more efficient than their two-component counterparts. Kinetic studies based on microcalorimetry revealed a significant increase in polymerization rate with increasing concentration of N-alkoxypyridinum salt. Such results were not obtained for photoinitiating systems possessing 1,3,5-triazine derivative as a second coinitiator. Based on the experimental results we concluded that the primary photochemical reaction involves electron transfer from the borate anion to the excited dye followed by the reaction of resulting dye-based radical with second coinitiator that regenerates the original dye and simultaneously produces the alkoxy radical or triazynyl radical which could start the polymerization chain reaction.