Design and characterization of self-healing, shape-memory non-isocyanate polyurethanes with tunable nanostructure and mechanical properties

Abstract

Polyurethanes (PUs) represent one of the most versatile classes of polymers, yet their conventional synthesis relies on toxic isocyanates, posing challenges for sustainable development. Here, we present a scalable and environmentally benign strategy for producing multifunctional non-isocyanate polyurethanes (NIPUs) with performance competitive with that of isocyanate-based analogues. Using a simple, solvent-free, two-step process and commodity monomers, the materials were obtained in quantitative yields (>98%) without hazardous reagents or complex catalysts. Structural and thermal analyses confirmed well-defined nanophase separation and tunable crystallinity, enabling precise control over the mechanical and functional properties. The NIPUs demonstrated tensile strengths of up to 8.93 MPa and elongations at break exceeding 240%, together with remarkable self-healing efficiencies (up to 98%) and excellent shape-memory behavior, with shape-fixity and shape-recovery ratios above 90%. Dynamic interfacial processes associated with the softening of the semicrystalline PCL domains, together with reversible hydrogen bonding, shape-memory-assisted crack closure, and the likely contribution of dynamic disulfide exchange, collectively contributed to the excellent self-healing performance. By uniting green chemistry with advanced performance, this work narrows the long-standing gap between NIPUs and conventional PUs, establishing a sustainable platform for next-generation smart materials for adaptive coatings and flexible electronics.