Phenacyl Phenothiazinium Salt as a New Broad‐Wavelength‐Absorbing Photoinitiator for Cationic and Free Radical Polymerizations

A novel broad‐wavelength‐absorbing photoinitiator based on phenacyl phenothiazinium hexafluroantimonate (P‐PTh) possessing both phenacyl and phenothiazine chromophoric groups was reported. P‐PTh absorbs light at UV, Visible and Near‐IR region. Photophysical, photochemical, and computational investigations revealed that P‐PTh in solution decomposes at all wavelengths by homolytic and heterolytic cleavages and generates cationic and radical species, which could efficiently initiate cationic and free radical polymerizations. It is anticipated that the photoinitiator with such wavelength flexibility may open up new pathways in curing applications of formulations of pigment systems.