Phenothiazine-based charge-transfer complexes as visible-light photoinitiating systems for acrylate and thiol-ene photopolymerization

Owing to their unique photodynamics, phenothiazine (PTZ) can be used to form charge-transfer complexes (CTCs), which serve as effective visible-light photoinitiating systems (PIS) for acrylate and thiol-based click polymerization. In this study, seven PTZ structures and their corresponding CTCs with iodonium salt (Iod) were evaluated by calculated spectra and polymerization kinetics. The effectiveness of the initiator decreased in the order of N-substituted polycyclic aromatic hydrocarbons > electron-donating aromatics > electron-withdrawing aromatics ≈ aliphatic alkanes. Substituted dimethylaminophenyl derivatives exhibited a lower energy gap and higher photoinitiation efficiency in CTCs. Moreover, PTZ-based CTCs as PIS rendered increased thermal stability to the photosensitive resin systems due to the mild free-radical quenching of PTZ. Such characteristic demonstrates potential versatility in the 3D printing of high-performance and high-precision materials. [Display omitted] •Seven PTZ-based CTCs show efficient photoinitiating capability in acrylate and thiol-ene systems.•Structure/interaction relationships for PTZs have been given.•Good thermal stability to photosensitive systems indicates a huge application potential.