Lignin-derived soft templates for the green synthesis of hollow phenolic resin nanocages and their multifunctional applications

The development of multifunctional nanomaterials with unique structural and functional properties is a critical area of research in materials science; however, their synthesis is full of challenges. Herein, we firstly reported a simple synthesis strategy for fabricating resin-based hollow nanocages (RHNCs) with controllable sizes and a unique hollow nanostructure, which exhibited potential for a wide range of multifunctional applications. RHNCs were synthesized using lignin as a soft template through a gradient polymerization process of resin nanospheres, followed by the removal of lignin templates via ethanol dissolution, resulting in the formation of a spherical shell structure with well-defined pores. Lignin addition regulated RHNCs' particle size and morphology while enhancing their specific surface areas and application values. The RHNCs exhibited excellent dispersion stability in various media, attributed to their smaller particle size and greater exposure of hydrophilic functional groups. Additionally, the resulting RHNCs possessed notable antioxidant activity and favorable biocompatibility. As nano-reinforced fillers, the addition of a small amount of RHNCs significantly improved the mechanical performance of polymer materials, owing to cross-linking through interpenetrating networks and reinforcement provided by hydrophobic rigid structures, particularly in terms of tensile strength, elongation at break, and toughness. Furthermore, RHNCs can serve as efficient free radical initiators for hydrogel polymerization, reducing the gelation time to within seconds at room temperature without the need for external stimuli. The unique synthesis strategy and multifunctional properties of RHNCs open new avenues for the development of advanced nanomaterials with tailored properties for specific applications.