Efficient visible photoinitiator with high-spectrum stability in an acid medium for free-radical and free-radical-promoted cationic photopolymerization based on erythrosine B derivatives

Three dye-linked photoinitiators with excellent spectral stability in an acid medium were synthesized by the covalent bonding of a coinitiator (tertiary amine) and a benzoyl group or two coinitiators to the phenolic and carboxyl group position of erythrosine B. The combination of the iodonium salt and free tertiary amino used to initiate the free-radical/cationic visible photopolymerization was investigated to acquire the relationship between the structure and performance. The photoinitiating ability of the derivative with the phenolic position bearing a coinitiator was poorer than of the derivative with the carboxyl group bearing one because of the strong back electron transfer of the former. For the derivative with a linked coinitiator on the carboxyl position, the proximity effect between the sensitizer and the coinitiator moiety resulted in an excellent photoinitiating ability for radical/cationic polymerization; this suggested its potential for application. Although radical/cationic photopolymerization could be initiated by the derivative/coinitiator/iodonium salt, the different component ratios between them had different effects on these two polymerizations; this provided useful information for the design of effective photoinitiators for different polymerizations. On the basis of the fluorescence quenching and photopolymerization results, a corresponding synergistic mechanism was proposed. (C) 2015 Wiley Periodicals, Inc.