Abstract
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.
Highlights
Light is involved in various chemical processes and its use in polymer science is growing in great strides
The growing interest in cationic photopolymerization prompts the search for new types of photoinitiators because the efficiency of polymerization depends on their properties
It has been shown that the iodonium salt cation, as an electromagnetic radiation absorbing component, is responsible for the photochemical properties of these compounds as photoinitiators
Summary
Light is involved in various chemical processes and its use in polymer science is growing in great strides. Polymerization using light was initially used exclusively in the film-forming industry in the production of solvent-free paints and varnishes.[1] Currently, photopolymerization is used in a large number of applications, such as the production of printed circuits,[2] lenses,[3] and photosetting adhesives.[4] The development of photosensitive materials enables printing on various substrates, such as plastics, metal, or wood. In addition to dental materials[5−7] in medicine, photosensitive materials have found applications in the manufacture of limb implants, plastic and reconstructive surgery,[8,9] or the production of medical hydrogel materials.[10,11] An essential technique in recent years has become 3D printing according to the one-photon and twophoton (2PP) mechanisms, enabling the production of objects with high resolution.[12,13]
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