Synergistic reinforcement of bio-based non-isocyanate polyurethane by nanocellulose and lignin.

With the growing global demand for sustainable polymeric materials, bio-based non-isocyanate polyurethanes (NIPU) have attracted considerable attention as environmentally friendly alternatives to conventional polyurethanes. However, simultaneously achieving high performance and multifunctionality in NIPU remains challenging. Although nanocellulose (NCs) and lignin (Lig) have been widely employed as bio-based fillers, their potential synergistic effects in NIPU systems remain insufficiently understood. In this study, epoxidized soybean oil (ESO) was converted into cyclic carbonate soybean oil (CSBO) using a deep eutectic solvent (DES)-catalyzed system. The CSBO was then cured with 4,4'-dithiodianiline diamine (DDA) to construct a dynamic dual-network NIPU. Subsequently, NCs and Lig were incorporated as reinforcing components to fabricate NCs/Lig/NIPU composites. The results demonstrated that the synergistic incorporation of NCs and Lig substantially enhanced the overall performance of the composites, including their mechanical properties, thermal stability, and surface hydrophobicity. Moreover, the synergistic effects of dynamic disulfide exchange and multiple hydrogen-bonding interactions endowed the composites with excellent shape-memory behavior and self-healing capability. These composites also exhibited good cyclic stability. These features highlight the strong potential of NCs/Lig/NIPU composites for intelligent packaging applications. Overall, this study provides a promising strategy for constructing high-performance, multifunctional bio-based polyurethane materials and offers further insights into the synergistic reinforcement mechanisms of natural components in bio-based NIPU systems.