Photothermal dual-curing cellulose/castor oil-derived thermosetting resin with enhanced mechanical performance, structural stability, and reparability for 3D printing.

The development of high-performance bio-based thermosetting resins for 3D printing is highly desirable in engineering applications. However, conventional photocurable 3D printing resins are limited by unsatisfactory mechanical properties and structural stability due to insufficient molecular weight growth under UV irradiation and weak interlayer bonding. Herein, we developed a bio-based thermosetting resin with excellent mechanical properties, structural stability, and reparability via photothermal dual-curing 3D printing technology. A castor oil-derived monomer bearing both acrylate groups and hindered urea bonds (HUBs) was first synthesized and blended with ethyl cellulose macromonomers, 2-hydroxyethyl acrylate, isophorone diisocyanate (IPDI), and photo-initiator to prepare photosensitive resins. During the 3D printing stage, photo-initiated radical polymerization of monomers generated the first crosslinking network in the photo-cured resin. Subsequent thermal treatment promoted the reaction between the isocyanate (-NCO) groups of IPDI and the hydroxyl groups of the monomers, thereby enhancing the interlayer bonding strength and forming a dual-crosslinked network. The photothermal dual-cured resin exhibits significantly improved mechanical strength of 26.34 MPa and toughness of 20.01 MJ/m3, achieving 1.56-fold and 1.64-fold increase than photo-cured resin, respectively. The incorporation of HUBs endows the resin with excellent reparability, achieving a mechanical strength recovery efficiency of 102.94%. Notably, the bio-thermosetting resin can be printed into complex three-dimensional architectures and demonstrates considerable potential for applications in lightweight, high-strength structural support components and thermo-responsive shape memory grippers.