UV-curable thiol-ene networks with intrinsic antioxidant functionality from eugenol-derived triallyl isocyanurate

The development of bio-based polymers with intrinsic antioxidant functionality offers a sustainable strategy to enhance material longevity and stability while reducing reliance on migratory additives. Herein, a triallyl isocyanurate monomer (TEG) was synthesized via the reaction of eugenol, a renewable phenolic compound, with thermally stable hexamethylene diisocyanate isocyanurate. TEG was subsequently employed to construct functional thiol-ene networks through UV-initiated thiol-ene photopolymerization with multifunctional thiols. Additional formulations incorporating pristine eugenol were designed to preserve pendant phenolic hydroxyl groups, thereby imparting enhanced radical-scavenging capacity. The photopolymerization kinetics, monitored by real-time FTIR and photo-DSC, revealed rapid curing with high thiol conversion (≈78%) achieved within 2 min of irradiation. A slight retardation (conversion ≈72%) was observed in systems containing pendant phenolic hydroxyl due to their free radical quenching effect. Dynamic mechanical analysis confirmed that increasing thiol functionality led to higher crosslink densities and elevated glass transition temperatures (Tg = 16–38 ◦C), while tensile testing demonstrated tunable stiffness (Et = 1.2–54.3 MPa) and elongation (εM = 47–63%). The resulting networks exhibited excellent optical transparency (>80% transmittance at 500 nm), effective UV-shielding (~0% transmittance below 320 nm), and outstanding thermal stability (Tmax ≈ 320 and 460 ◦C). DPPH assay verified strong intrinsic antioxidant activity especially for phenolic hydroxyl containing formulations, achieving up to 86% radical scavenging. Collectively, these findings establish a sustainable design approach for multifunctional thiol-ene networks that unite mechanical adaptability, UV protection, thermal robustness, and built-in antioxidant functionality, suitable for applications in flexible coatings, packaging, and protective materials