Design of novel phenothiazine-based push-pull photoinitiators for visible light with high activity, good solubility and low migration

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. • Four novel phenothiazine-based push-pull photoinitiators were synthesized. • Two-component photoinitiator system can significantly improve the photopolymerization efficiency. • All novel photoinitiators have good solubility in different solvents and monomers. • All novel photoinitiators shown low migration ratio and low cytotoxicity performance.