Lignin Derivative as Visible-Light Photo-Initiating System for the Development of Biocide Materials under Light Irradiation

The design of a new visible-light methacrylated-based kraft lignin photosensitizer (MAcL) of iodonium salt (Iod) for the free-radical polymerization (FRP) of polyethylene glycol dimethacrylate (PEGDMA) under LEDs@405, 455, 470, 505, and 530 nm is reported. As demonstrated by laser flash photolysis (LFP) and electron paramagnetic resonance spin-trapping (EPR ST) experiments, the combination of MAcL with an electron acceptor (Iod) and trimethylolpropane tris(3-mercaptopropionate) (TT) used as a crosslinker, leads to the formation of highly efficient initiating radicals, i.e., thyil and carbon-centred radicals, promoting thus the FRP of PEGDMA. The final methacrylate conversions of PEGDMA are very high and range from 80 to 95% under LED@530 nm and LED@405 nm, respectively. For the first time, MAcL is also used as a biocide agent as it produces singlet oxygen when exposed to visible light. The resulting photoinduced bio-based materials incorporating MAcL demonstrate tremendous antibacterial properties against Staphylococcus aureus (S. aureus), inducing 100% bacterial death.