A Charge‐Transfer Complex of Thioxanthonephenacyl Sulfonium Salt as a Visible‐Light Photoinitiator for Free Radical and Cationic Polymerizations

Abstract

A new double chromophoric sulfonium salt photoinitiator possessing both thioxanthone and phenacyl groups, namely 2isopropylthioxanthonium phenacyl hexafluoroantimonate (ITX-PhenS), was synthesized and characterized. ITXPhenS can form a charge-transfer complex (CTC) with the donor N,N-dimethyl aniline (DMA) with absorption characteristics in the visible range as confirmed by spectral analysis, cyclic voltammetry (CV) and density functional theory (DFT). The extension of the absorb-ance shift can be controlled by the ITXPhenS to DMA ratio. The ability of the CTC to initiate free radical and cationic polymerization reactions of various monomers under visible and natural sunlight is demonstrated. The proposed mechanism assumes the generation of radical and ionic species by the heterolytic and/or homolytic cleavage of ITXPhenS within the CTC followed by electron-transfer reactions.

Flavones as natural photoinitiators for light mediated free‐radical polymerization via light emitting diodes

“…The final photoreaction proposed is not to occur through classical dye/quencher interaction: as recently published, NPG can act as an electron donor to for, a CTC with iodonium acceptor . CTCs have been reported as photoinitiators of several resins . The experimental data of Figure S1 validate such an interaction.…”

Review on UV-Induced Cationic Frontal Polymerization of Epoxy Monomers

“…Several photoinitiator systems based on charge transfer complex have also been reported in the cationic polymerization of epoxides [ 99 , 100 , 101 , 102 ]. In one study, Garra et al [ 103 ] reported a charge transfer complex (CTC) based on mixture of N -phenylglycine and iodonium salt (NPG-Iod) CTC that proved to be an efficient photoinitiating system in cationic polymerization of bis-cycloaliphatic epoxy monomer, enabling a curing under LED irradiation with a wavelength of 405 nm.…”

Charge Transfer Complexes based on Various Amines as Dual Thermal and Photochemical Polymerization Initiators: A Powerful Tool for the Access to Composites

“…Recently applied CTCs based on phosphine, aniline, pyrrole, and indole acceptors were exploited as photo/thermal dual initiators but without systematic study . Some amine/Iodonium salt CTCs were also reported to initiate cationic polymerization .…”

“…9,26 Recently applied CTCs based on phosphine, aniline, pyrrole, and indole acceptors were exploited as photo/thermal dual initiators but without systematic study. [24][25][26][27][28] Some amine/ Iodonium salt CTCs were also reported to initiate cationic polymerization. 13 In this article, a series of amines will be systematically investigated to find out the impacts of the amine structure on the CTCs' initiation performance (Scheme 1).…”