Methacrylated Biosyrups of Depolymerized Lignin for Radiation-Curable Bioaromatic Resins and Functional Nanoscale Coatings

Radiation-curable resins display some intrinsic sustainable advantages since they are solvent-free and require less energy to cure but are still largely derived from fossil resources. This lack of renewability is especially notable for the important class of aromatic precursors that impart unique properties to the final materials. Herein, we report a new class of photocurable resins derived from depolymerized lignin oil, an emerging class of bio-oil containing low molecular weight bioaromatic compounds such as lignin monomers, dimers, and small oligomers. To do so, we implemented a two-step green synthetic pathway involving ethoxylation of phenolic hydroxyls with ethylene carbonate followed by trans-esterification of aliphatic hydroxyls with methyl methacrylate, thus circumventing the use of traditional (and often toxic) acrylation reagents. This innovative approach was first applied to monomeric (hydroxy)alkylphenol model compounds, and then directly to a pinewood-derived lignin oil . Highly functionalized methacrylated bioaromatic precursors were obtained directly as viscous liquids (without adding reactive diluents), thus mimicking the acrylic “syrups” commonly used in industry. These reactive biosyrups were then UV-cured into functional materials, such as free-standing films and (nanoscale) coatings, and their superior thermomechanical properties were thoroughly investigated, revealing important insights in their tunable structure–property relationships. In summary, we introduce a new class of radiation-curable bioresins leveraging synergies between the sustainable benefits of UV systems and the unique bioaromatic structure of lignin oil and demonstrating significant potential for a wide range of applications in the coatings, microelectronics, nanotechnology, or biomedical industries.