Design of novel phenothiazine-based push-pull photoinitiators for visible light with high activity, good solubility and low migration
Lin Deng, Jinqing Qu
Abstract
Using phenothiazine as electron donor group, four novel visible light photoinitiators (10-methyl-phenothiazine-2-yl) (phenyl)methanone (MPO), (10-methyl-phenothiazine-2,8-diyl) bis(phenylmethanone) (MPBO), (E)-1-(10-methyl-phenothiazine-2-yl)-3-phenylprop-2-en-1-one (MPPO) and (2E,2′E)-1,1′-(10-methyl-phenothiazine-2,8-diyl) bis(3-phenylprop-2-en-1-one) (MPBPO) with D-A structure were synthesized by one-step method. The effect of conjugated structure and C C bond on the photophysical properties, solubility and migration ratio was discussed. With the degree of conjugation and the number of C C bond increases, the maximum absorption wavelength redshifted from 385 nm (MPO) to 414 nm (MPBO) and 400 nm (MPPO) to 430 nm (MPBPO) respectively. The charge transfer between the two-component photoinitiator system (Iod as co-initiator) can significantly improve the photopolymerization efficiency, the final C C double bond conversion can reach to 80 %, and the drying time of coatings was within 5–20 s. Moreover, all MPO, MPBO, MPPO and MPBPO have good solubility in different solvents and monomers . In addition, MPO, MPBO, MPPO and MPBPO shown low migration ratio and low cytotoxicity performance.