Different photoinitiating ability and photobleaching efficiency of erythrosine B derivatives in radical/cationic photopolymerization

A series of erythrosine B derivatives with a linked coinitiator on different position, combined with iodonium salt and/or tertiary amine were used to initiate free radical/cationic photopolymerization. Their photoinitiating ability and photobleaching behaviors were investigated and compared with those of the systems containing separated counterparts. The polymerization results showed that compared to the systems containing separated counterparts, the systems containing derivatives with a linked coinitiator on carboxyl group exhibited higher photoinitiating ability in radical photopolymerization, but had poorer one in cationic polymerization. Simultaneously, in free radical/cationic polymerizations, these linked derivatives could be photobleached more efficiently than the separated one, due to fast intramolecular reaction, which was especially significant for the industrial application. Besides, it was found that the investigated systems were photobleached more efficiently in cationic photopolymerization than in radical one. These results will provide useful information for designing effective photoinitiators for different polymerization.