β-Carotene/Limonene Derivatives/Eugenol: Green Synthesis of Antibacterial Coatings under Visible-Light Exposure

This study reports for the first time the use of beta-carotene as a natural photosensitizer for both the cationic photopolymerization and thiol-ene click reactions under visible-light irradiation. In an all-green synthesis approach, this performing dye-based system leads to the cationic and thiol-ene polymerization of bio-based monomers, mono- and di-epoxy limonene, with very high final conversions, and appears as efficient as the common visible-light photosensitizers used in free-radical or cationic photopolymerization, that is, thioxanthone derivatives or camphorquinone. Effective antibacterial and tack-free coatings have been synthesized through the incorporation of a natural antibacterial agent (eugenol) in the limonene-derived polymer network. The antibacterial assays have demonstrated a tremendous effect of the eugenol-containing coatings against the adhesion of Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive).