A Bio-Based Non-Isocyanate Polyurethane with Good Mechanical Properties, Effective Self-Healing Capability, and High Chemical Recyclability

Against the backdrop of green and sustainable development in the polyurethane industry, nonisocyanate polyurethane (NIPU) has increasingly attracted attention as a promising alternative. Among various synthetic strategies, the synthetic route using cyclic carbonates and polyamines to prepare NIPU stands out for its exceptional application potential. In this study, soybean oil-based cyclic carbonate (TSO) was synthesized from soybean oil and thioglycerol under atmospheric pressure. Subsequently, a series of nonisocyanate polyurethanes (S-NIPU) with high biobased content were prepared through copolymerization of TSO with biobased diamines. Different from conventional linear NIPU, TSO provides multifunctional cyclic carbonate groups, enabling the formation of a three-dimensional cross-linked network upon amination. This robust network structure significantly enhances both the thermal stability and mechanical properties of S-NIPU. The results demonstrate that S-NIPU exhibits excellent and tunable tensile properties, with a tensile strength of 2.4 MPa and an elongation at break of 139%. Simultaneously, owing to the dynamic interactions between carbamate and hydroxyl groups, as well as multiple hydrogen-bond rearrangements, S-NIPU displays outstanding self-healing capability. Following thermal treatment, the self-healing efficiency reaches up to 94%. Furthermore, S-NIPU can be chemically recovered, reprocessed, and recycled in ethanol solutions. After three recycling cycles, it retains 91% of its original mechanical performance. This work begins with molecular structure design and employs a green, facile strategy to synthesize biobased S-NIPU materials, which exhibit significant potential for applications in coatings and adhesives.