Terpenes, natural dyes and photochemistry: toward the synthesis of photoactive bio-based materials with biocide properties†

Combining bioresources and photo-induced polymerization is a promising way to design sustainable and high-performing antibacterial materials. In this study, we propose a green synthesis of bio-based materials with dual antibacterial properties by photopolymerization. Two new methacrylate-based hydroxyanthraquinones derived from purpurin and alizarin (P-3Ac and Al-2Ac) have been designed to promote the polymerization of bio-based vegetable oil and terpene blend mixtures under visible-light irradiation up to 470 nm. All the photochemical mechanisms involved in the photopolymerization processes have been described by steady state photolysis, electron spin resonance spin-trapping (ESR ST) and real-time Fourier transform infrared (RT-FTIR) spectroscopy. Interestingly, the photo-initiating properties of P-3Ac and Al-2Ac are greatly enhanced in comparison with the native unmodified purpurin and alizarin. Polymerization of soybean oil acrylate and linalool through a thiol–ene process has led to the formation of photoactive bio-based materials able to generate biocide reactive oxygen species (ROS) upon light exposure which can also be used as contact-killing materials for tremendous inhibition of bacterial growth. The respective effects of each biocide agent (ROS and linalool) were compared and combined, highlighting stunning inhibition properties of the materials (higher than 99.99%) against both E. coli (Gram negative) and S. aureus (Gram positive), even after a second antibacterial recycling test. Prior to photo-printing experiments, rheological studies have been performed to design greener 3D-photoinduced materials. According to the high bio-renewable carbon contents of the photosensitive P-3Ac-based formulation and its great processability, 3D objects have been designed using Digital Light Processing (DLP) technology upon 405 nm light emitting diode exposure.