Design and Performance Tuning of Degradable, Biomass-Based Self-Healing Cross-Linked Polythioureas

The environmental impact and limited reparability of traditional polymer materials have created an urgent demand for sustainable, long-lasting alternatives. Although self-healing covalent adaptable networks (CANs) can extend material service life, most current systems still rely on petroleum-based feedstocks and lack controllable degradability. Through molecular design, this study has constructed a class of biomass-based self-healing cross-linked polythioureas. With dynamic thiourea bonds as the core, biomass derivatives such as chitosan, aminated cellulose, aminated lignin, aminated starch, and aminated xylan were cross-linked with diisothiocyanates via catalyst-free click reactions, yielding polymer networks that integrate excellent self-healing ability, reprocessability, and tunable degradability. Systematic investigation demonstrates that the materials achieve high-efficiency self-healing (efficiency >73%) under mild conditions and possess complete reprocessing capability. By adjusting the biomass type, cross-linked network structure, and dynamic bond content, the mechanical properties can be effectively tuned, with tensile strength from 14.36 to 48.91 MPa, and elongation at break ranging from 738.94% to 1887.06%. Moreover, the materials exhibit biodegradability in soil, with a maximum mass loss exceeding 40% within 120 days, achieving a closed-loop life cycle from renewable feedstocks to environmental degradation. This work provides a feasible molecular design strategy for balancing material performance, reparability, and ecological compatibility.