Castor Oil-Derived Ionic Liquids for Flexible, Antibacterial Biobased Thermosetting Polymers via Thiol–Ene Click Chemistry

The escalating threat of bacterial infections highlights the urgent need for flexible antibacterial biobased resin materials. In this study, castor oil was transformed into imidazole-based ionic liquids (<b>c1</b> and <b>c2</b>) via a two-step atom-economic synthesis. Thermosetting resins were fabricated through UV-thermal dual-cured thiol-ene click polymerization of <b>c1</b>/<b>c2</b> with multifunctional thiol monomers. A biobased aromatic α,ω-diene carbonate monomer (<b>d</b>) was introduced to modulate the network structure. Thermal curing behavior was optimized by using NMR and FTIR analyses. Tensile testing identified <b>Pc1</b>_<b>1</b><b>d</b>_<b>9</b><b>-4SH</b> and <b>Pc2</b>_<b>1</b><b>d</b>_<b>9</b><b>-4SH</b> as optimal formulations, exhibiting tensile strengths of 9.42 and 9.08 MPa, elongation at break of 279.9% and 280.0%, and a glass transition temperature around 15 °C. DMA and TGA confirmed their viscoelastic behavior and thermal stability, while AFM/SEM revealed phase-separated microstructures contributing to enhanced mechanical properties. Antibacterial tests demonstrated exceptional efficacy (99.9% inhibition) against common pathogens. By integrating molecular design and process innovation, this work establishes a biobased resin system combining flexibility, thermal stability, and potent antibacterial activity, offering a novel strategy for developing infection-resistant biomedical materials.