One-Component Cationic Photoinitiators from Tunable Benzylidene Scaffolds for 3D Printing Applications

This paper describes a series of novel benzylidene scaffold-based iodonium salt one-component photoinitiators containing double bonds and dialkylamino groups synthesized in one step via classical aldol condensation reactions. Systematic investigations of structure-activity relationships were performed via quantum-chemical calculations and experimental tests. New salts can efficiently decompose under irradiation from UV to visible regions of the spectrum. The design of new iodonium salts is described, followed by a description of properties of photoinitiators prepared in this way. All presented salts were characterized in terms of their spectral properties (UV-vis spectroscopy), ability to photodecompose (steady-state photolysis), cationic polymerization of the vinyl monomer, and epoxide monomer photoinitiation (quantum efficiency of acid generation and real-time Fourier-transform infrared measurements) as well as their proposed application in 3D printing. New benzylidene iodonium salts can photoinitiate the polymerization of vinyl ethers and epoxy monomers under LED@365 and LED@405 irradiation. Investigated compounds can simultaneously initiate and monitor the polymerization process according to the change of fluorescence during the photocuring process. Formulations before photopolymerization do not exhibit fluorescence, during the photopolymerization process fluorescence is turning on. This phenomenon might be used to monitor photopolymerization in an online manner.

Automated summary

This paper presents a novel method for synthesizing benzylidene iodonium salts as photoinitiators and investigates their properties, showing efficient decomposition under UV to visible light and potential application in 3D printing.