Abstract
Novel 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were proposed as photosensitizes of iodonium salt for a highly effective bimolecular photoinitiating system upon soft irradiation conditions under long-wave ultraviolet (UV-A) and visible light. Remarkably, these structures are highly versatile, allowing access to photoinitiating systems for the free-radical polymerization of acrylates, the cationic photopolymerization of epoxides, glycidyl, and vinyl ethers, the synthesis of interpenetrated polymer networks (IPNs) and the thiol-ene photopolymerization processes. Excellent polymerization profiles for all of the monomers, along with the high final conversions, were obtained. The initiation mechanisms of these bimolecular systems based on the 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were investigated using the real-time FT-IR technique, steady-state photolysis, fluorescence experiments, theoretical calculations of molecular orbitals, and electrochemical analysis. Moreover, the 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were investigated as a type II free-radical photoinitiator with amine. It was confirmed that the 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives, in combination with different types of additives, e.g., amine as co-initiator or in the presence of onium salt, can act as a bimolecular photoinitiating system via the photo-reduction or photo-oxidation pathways, respectively.
Highlights
The field of photopolymerization has been one of the most widely and rapidly growing industries in recent years [1,2]
We describe bimolecular photoinitiating systems operating in the long-wave ultraviolet (UV-A) and visible light range, where 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were selected as the effective photosensitizes
The UV−Vis spectra of the 2-amino-4-methyl-6-phenyl-benzene-1,3-dicarbonitrile derivatives were recorded in acetonitrile to determine the maxima of the absorption characteristics and the corresponding extinction coefficient at an absorption maximum wavelength (Table 1 and Figure 1a,b)
Summary
The field of photopolymerization has been one of the most widely and rapidly growing industries in recent years [1,2]. IPN photopolymerization carried out in this way causes problems at the stage of selecting a photoinitiating system; this type of process allows to obtain materials with completely innovative functional, mechanical, and strength properties, which are not available when conducting photopolymerization of one type of monomer For this reason, the development of efficient versatile photoinitiating systems remains a great challenge. The photochemical mechanisms were studied through steady-state photolysis, fluorescence experiments, theoretical calculations of molecular orbitals, and electrochemical analysis This approach allowed the study of the structure/reactivity/efficiency relationships of the investigated biphenyl derivatives as photosensitizes of iodonium salt in cationic, free-radical, and IPN photopolymerization under low intensity LED light sources. Different types of compositions for 3D printing are proposed, including IPN systems and copolymers
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