Novel and efficient dye-linked radical generators for visible light photoinitiating polymerization

Dye-linked initiators consisting of a benzothiazolylidene-rhodanine merocyanine dye (M) and a substituted bis(trichloromethyl)-1,3,5-triazine initiator (T) linked by a different number of methylene units and at different positions were prepared in order to reveal the effect of the structure of linked systems on the efficiency of photopolymerization. The spectroscopic studies clearly showed that the dye-linked initiators exhibit a marked increase in the efficiency of photobleaching and fluorescence quenching compared to a simple mixture of the dye/initiator and that the efficiency among the linked systems is dependent on the number and position of methylene units. These results are reasonably explained in terms of the efficiency of electron transfer between the dye and the initiator, which eventually results in the formation of a radical. The relative photoinitiating efficiency of dye-linked initiators in photopolymerization of acrylates was also evaluated and the trends observed for polymerization are essentially the same as that observed spectroscopically.